Coastal Construction Manual

Pile Buck ®, Inc.

NOTICE:The compilation of handbooks on this CD-ROM and the material contained within isprovided without warranty of any kind. Pile Buck®, Inc. hereby disclaims any and allexpress or implied warranties of merchantibility, fitness for any general or particularpurpose or freedom from infringement of any patent, trademark, or copyright inregard to information or products contained or referred to herein. Nothing hereincontained shall be construed as granting a license, express or implied, under anypatents. Anyone making use of this material does so at his or her own risk andassumes any and all liability resulting from such use. The entire risk as to qualityor usability of the material contained within is with the user. In no event will PileBuck®, Inc. be held liable for any damages including lost profits, lost savings or otherincidental or consequential damages arising from the use or inability to use theinformation contained within. Pile Buck®, Inc. does not insure anyone utilizing thismaterial against liability arising from the use of this information and hereby will notbe held liable for "consequential damages," resulting from such use.

Steel Sheet Piling • Timber Piles • Foundations • Geotechnical Engineering • Marine Docks • Marinas • Bridge Building • Dredging •

Pile Hammers • Pipelines • Jetties • Breakwaters • Barges • Cranes • Cofferdams • Harbors • Piers • Wharves • Soils • Moorings •

Bulkheads • Earth Retaining Structures • Ports • Seawalls •Steel Sheet Piling • Timber Piles • Foundations • Geotechnical Engineering

• Marine Docks • Marinas • Bridge Building • Dredging • Pile Hammers • Pipelines • Jetties • Breakwaters • Barges • Cranes •

Cofferdams • Harbors • Piers • Wharves • Soils • Moorings • Bulkheads • Earth Retaining Structures • Ports • Seawalls • Steel Sheet

NEWSPAPERBOOKS

CD ROMSSOFTWARE

To obtain passwords to unlocksecured manuals, contact:

Pile Buck ®, Inc.P.O.Box 1736

Palm City, FL U.S.A. 34991

Phone: (561) 223-1919 • Fax: (561) 223-1995e-mail: [email protected] • www: http://www.pilebuck.com

©Copyright 1997 Pile Buck®, Inc. All Rights Reserved.

Coastal Construction Manual

Federal Emergency Management Agency FEMA-55/ February, 1986

ACKNOWLEDGMENTS

This report was prepared under contract EMW-84-C-1738 withthe Federal Insurance Administration (FIA) of the FederalEmergency Management Agency (FEMA), with additionalsupport from the National Oceanic and AtmosphericAdministration (NOAA), Office of Ocean and Coastal ResourceManagement.

January 1986

FOREWORD

This document is the second edition of the Design and Construction Manual for Residential Buildings in Coastal High Hazard Areas ( Coastal Construction Manual) , developed bythe Federal Insurance Administration (FIA) of the FederalEmergency Management Agency (FEMA) and published inJanuary 1931. It provides technical guidance on how to designand construct buildings in areas subject to coastal flooding,such that the potential risk of damages from both flood andwind are minimized. The technical criteria contained in thismanual can be used to comply with the performance standardsof the National Flood Insurance Program. It is intended for useby designers, builders, developers, community buildingofficials, and the homeowner. Changes to the 1981 manualinclude:

• Design guidance for breakaway wall enclosures • Design equations and procedures and listings of the

computer programs used in the manual • Revision of the design procedures to reflect the 1982 ANSI

standards and other recent design information • A chapter on larger structures (mid-rise and high-rise

buildings) • A sample construction code for coastal areas • A new section on the maintenance of coastal buildings • Additional information on construction cost

The intent of this manual is not to encourage building incoastal flood plains. Rather, when such building does occur, itis to help ensure that it be designed and constructed in amanner that minimizes the potential for flood and winddamage.

DISCLAIMER

The statements, recommendations, and procedurescontained in this manual are those of Dames & Moore andBliss & Nyitray, Inc., and do not necessarily reflect the views ofthe U.S. Government in general or the Federal EmergencyManagement Agency in particular. Dames & Moore and Bliss& Nyitray, Inc., warrant that their services were performed withthe usual thoroughness and competence of the consultingengineering profession, and no other warranty, eitherexpressed or implied, is included or intended.

This manual was developed to provide guidance andminimum requirements for coastal residential structures. Theuser must assume responsibility for adapting and/orsupplementing the information contained herein to meet theparticular requirements of a project. It is intended that thismanual complement state and local codes and ordinances,whose provisions should prevail in the event of conflict.

TABLE OF CONTENTS v

ACKNOWLEDGMENTS ii

FOREWORD iii

DISCLAIMER iv

TABLE OF CONTENTS v

LIST OF FIGURES xv

LIST OF TABLES xxi

CHAPTER 1: INTRODUCTION 1-1

1.1 PURPOSE AND SCOPE 1-1

1.2 NATIONAL FLOOD INSURANCE PROGRAM 1-2

1.2. 1 Emergency Program 1-3

1.2.2 Regular Program 1-3

1.2.3 Flood Plain Management 1-3

1.2.4 V Zones 1-4

1.2.5 A Zones 1-4

1.3 BUILDING CODES 1-5

CHAPTER 2: COASTAL ENVIRONMENT 2-1

2.1 NORTH ATLANTIC COAST 2-3

2.2 MIDDLE ATLANTIC COAST 2-6

2.3 SOUTH ATLANTIC COAST 2-7

2.4 GULF COAST 2-8

2.5 PACIFIC COAST 2-12

2.6 HAWAIIAN COAST 2-13

vi Coastal Construction Manual

CHAPTER 3: SITE DESIGN RECOMMENDATIONS 3-1

3.1 BUILDING CODE AND ZONING REQUIREMENTS 3-1

3.2 SITE LAYOUT 3-2

3.3 LANDSCAPING 3-2

3.4 DUNE PROTECTION 3-3

3.5 BULKHEADS 3-4

3.6 USE OF EARTHFlLL 3-6

CHAPTER 4: STRUCTURE DESIGN RECOMMENDATIONS 4-1

4.1 ENVIRONMENTAL FORCES 4-1

4.1.1 Wind 4-1

4.1.2 Salt Air, Moisture, and Wind-Driven Rain 4-7

4.1.3 Water, Waves, and Debris 4-8

4.1.4 Effects of Forces on Higher and Larger Structures 4-9

4.2 CONSTRUCTION MATERIALS 4-9

4.2.1 Wood 4-9

4.2.1.1 Piling 4-9

4.2.1.2 Main Supporting Members (Beams) 4-10

4.2.1.3 Other Wood Construction Members 4-10

4.2.1.4 Wood Preservatives 4-10

4.2.2 Masonry Materials and Concrete 4-11

4.2.3 Metals 4-11

4.2.3.1 Aluminum 4-11

4.2.3.2 Steel 4-11

4.2.3.3 Dissimilar Metals 4-11

Table of Contents vii4.3 DESIGN DETAILS 4-11

4.3.1 Foundations 4-11

4.3.1.1 Soil Conditions 4-12

4.3.1.2 Piles 4-13

4.3.1.3 Posts 4-18

4.3.1.4 Piers 4-18

4.3.2 Framing 4-20

4.3.2.1 Framing Methods 4-20

4.3.2.2 Beams 4-21

4.3.2.3 Joists and Rafters 4-22

4.3.2.4 Subflooring 4-22

4.3.2.5 Studs 4-23

4.3.2.6 Wall Sheathing 4-23

4.3.2.7 Wall Bracing 4-24

4.3.2.8 Roof Details 4-24

4.3.3 Foundation Bracing 4-27

4.3.3.1 Knee Braces 4-29

4.3.3.2 Grade Beams 4-29

4.3.3.3 Truss Bracing 4-30

4.3.3.4 Shear Walls 4-31

4.3.4 Connections 4-31

4.3.4.1 Roof to Wall 4-33

4.3.4.2 Wall to Floor Joists 4-35

4.3.4.3 Floor Joist to Floor Beam 4-35

4.3.4.4 Floor Beam to Pile, Post, or Pier 4-35

viii Coastal Construction Manual

4.3.5 Breakaway Walls 4-41

4.3.5.1 Breakaway Wall Designs 4-42

4.3.5.2 Design Considerations for Breakaway Walls 4-45

4.3.6 Utilities 4-50

4.3.7 Wind and Storm Protection of Interior 4-52

4.3.7.1 Window Selection 4-52

4.3.7.2 Operable Shutters 4-53

4.3.7.3 Gable and Eave Vents 4-54

4.3.7.4 Roofing Materials 4-54

4.3.8 Maintenance 4-54

CHAPTER 5: LARGER STRUCTURES 5-1

5.1 GENERAL DESIGN CONSIDERATIONS 5-1

5.2 FOUNDATIONS 5-2

5.3 SLABS AT GRADE 5-3

5.4 SUPERSTRUCTURE 5-4

5.5 ELEVATED FLOORS 5-7

5.6 EXTERIOR WALL SYSTEMS 5-8

5.7 RECOMMENDATIONS 5-9

CHAPTER 6: DESIGN PROCEDURES AND EXAMPLES 6-1

6.1 EXAMPLE 1--ELEVATION ON WOOD PILINGS 6-1

6.2 EXAMPLE 2--BRACING REQUIRED 6-11

6.3 EXAMPLE 3--BREAKAWAY WALLS 6-19

Table of Contents ix

APPENDIX A: DESIGN TABLES A-1

APPENDIX B: BRACING B-1

B.1 KNEE BRACING B-1

B.2 TRUSS BRACING B-1

B.2.1 Diagonals B-1

B.2.1.1 Lumber Diagonals B-2

B.2.1.2 Threadbar Diagonals B-4

B.2.2 Struts B-5

B.3 GRADE BEAMS B-6

APPENDIX C: DESIGN WORKSHEETS C-1

PILE DESIGN WORKSHEET 4 pp.

CONNECTION DESIGN WORKSHEET 2 pp.

BRACING DESIGN WORKSHEET 3 pp.

APPENDIX D: DESIGN EQUATIONS AND PROCEDURES D-1

D.1 PROCEDURE A-1: DOWNWARD LOADS PER PILE D-2

D.2 PROCEDURE A-2: HORIZONTAL WIND LOADS PER PILE D-3

D.3 PROCEDURE A-3: MINIMUM EMBEDMENT DEPTH OF PILES D-4

D.3.1 Square Piles D-4

D.3.1.1 Square Piles in Sand D-4

D.3.1.2 Square Piles in Clay D-6

D.3.2 Round Tapered Piles D-7

D.3.2.1 Round Piles in Sand D-7

D.3.2.2 Round Piles in Clay D-8

x Coastal Construction Manual

D.4 PROCEDURE A-4: MAXIMUM UNBRACED HEIGHT OF PILES D-9

D.4.1 Moment of Wave Forces D-10

D.4.2 Moment of Current Drag Forces D-11

D.4.3 Moment of Debris Impact Forces D-12

D.4.4 Moment of Wind Forces D-12

D.4.5 Allowable Bending Moment of Piles D-13

D.4.6 Maximum Unbraced Pile Height D-14

D.5 MAXIMUM UNBRACED HEIGHT FOR PILES SUPPORTING BREAKAWAY WALLS D-15

D.5.1 Moment of Wind Forces on Superstructure D-15

D.5.2 Moment of Breakaway Wall Forces D-15

D.5.3 Allowable Bending Moment in Piles D-15

D.5.4 Calculation of Maximum Unbraced Pile Height D-16

D.6 PROCEDURE A-5: UPLIFT LOADS PER FOOT OF WALL D-17

D.6.1 Rafter Connections D-17

D.6.2 Connections Between Stories D-19

D.6.3 Bottom Floor Connections (Two-story) D-20

D.7 PROCEDURE A-6: UPLIFT LOADS PER PILE D-21

D.7.1 Forces on Roof and Attic D-21

D.7.2 Uplift Forces on Second Story D-22

D.7.3 Uplift Forces on First Story D-22

D.7.4 Uplift at Top of Piles Due to Vertical Loads D-22

D.7.5 Uplift at Top of Piles Due to Moment D-23

D.7.6 Total Uplift at Top of Piles D-24

D.8 PROCEDURE B-1: HORIZONTAL WATER LOADS PER PILE D-25

D.8.1 Wave Forces D-26

Table of Contents xi

D.8.2 Current Drag Forces D-27

D.8.3 Debris Impact Forces D-28

D.8.4 Total Forces on Piles D-29

D.9 PROCEDURE B-2: LOADS TRANSFERRED TO FOUNDATION TRUSS MEMBERS D-30

APPENDIX E: COMPUTER PROGRAM LISTINGS E-1

DOWNLOAD E-2

UPNHORIZ E-3

EMBED E-5

UNBRACED E-6

CUBIC E-7

UNBR E-8

UPLIFT E-9

H2OLOADS E-11

TRUSS E-12

APPENDIX F: CONSTRUCTION COST F-1

F.1 FOUNDATIONS F-1

F.1.1 Wood Piles F-1

F.1.1.1 Types of Wood Piles F-1

F.1.1.2 Wood Pile Costs F-2

F.1.1.3 Pile Support F-4

F.1.2 Concrete Piles F-4

F.1.3 Pile Capsand Grade Beams F-4

F.1.4 Masonry and Concrete Piers F-4

F.1.5 Pile to Floor Beam Connections F-4

xii Coastal Construction Manual

F.2 STRUCTURAL BRACING F-4

F.2.1 Joist to Floor Beam Connection F-5

F.2.2 Stud Straps and Corner Bracing F-5

F.2.3 Roof Truss Connections F-5

F.3 ADDITIONAL COSTS F-5

F.3.1 Breakaway Walls F-6

F.3.2 Other Costs F-6

F.4 COST COMPARISON FOR ELEVATED AND NON-ELEVATED STRUCTURES F-6

APPENDIX G: SAMPLE COASTAL CONSTRUCTION CODE G-1

I. TITLE G-1

2. PURPOSE G-1

3. SCOPE G-2

4. DEFINITIONS G-2

5. ELEVATION STANDARDS G-3

6. DETERMINATION OF LOADING FORCES G-3

6.1 WATER LOADS G-3

6.2 WIND LOADS G-3

7. FOUNDATION STANDARDS G-4

7.1 PILE FOUNDATION DESIGN G-4

7.1.1 Pile Spacing G-4

7.1.2 Pile Embedment G-4

7.1.3 Column Action G-4

7.1.4 Pile Standards G-4

7.1.5 Pile Installation G-5

Table of Contents xiii

7.1.6 Bracing G-5

7.2 COLUMN FOUNDATION DESIGN G-5

8. ANCHORING STANDARDS G-5

8.1 CONNECTORS AND FASTENERS G-5

8.2 BEAM TO PILE CONNECTIONS G-5

8.3 FLOOR AND DECK CONNECTIONS G-6

8.4 EXTERIOR WALL CONNECTIONS G-6

8.5 CEILING JOIST/RAFTER CONNECTIONS G-6

8.6 PROJECTING MEMBERS G-6

9. ROOF SHEATHING G-6

10. PROTECTION OF OPENINGS G-7

11. USE OF SPACE BELOW THE LOWEST ELEVATED FLOOR G-7

11.1 BREAKAWAY WALL DESIGN STANDARDS G-7

11.2 CERTIFICATION OF BREAKAWAY WALLS G-7

12. UTILITIES G-8

13. CERTIFICATION REQUIREMENTS G-8

14. REFERENCE DOCUMENTS G-8

APPENDIX H: INDIVIDUALS CONTACTED DURING STUDY H-1

APPENDIX I: BIBLIOGRAPHY (References) I-1

LIST OF FIGURES xv

Figure 1-1 Home damaged by winds during Hurricane Elena 1-2

Figure 2-1 Hurricane experience of eastern United States, 1886-1970 2-4

Figure 2-2 The United States coastline 2-5

Figure 2-3 Representative beach profiles 2-7

Figure 2-4 Undermining of shallow supported foundations by beach erosion 2-10

Figure 2-5 Contrasting minor and major damage to two

adjacent houses during Hurricane Frederic 2-11

Figure 2-6 U-shaped structure damaged by Hurricane Frederic 2-11

Figure 2-7 Simple bulkhead 2-13

Figure 2-8 Typical bulkhead in Hawaii 2-14

Figure 2-9 Soil erosion potential 2-14

Figure 3-1 Typical dune reconstruction 3-3

Figure 3-2 Walkway structure and fencing protect the dune 3-3

Figure 3-3 Example of use of building setback requirements

to locate structures behind the primary dune 3-4

Figure 3-4 Zoning restrictions on coastal development 3-4

Figure 3-5 Erosion damage to individual bulkhead 3-5

Figure 3-6 Rock riprap used as a bulkhead 3-5

Figure 3-7 Concrete seawall with recurved face 3-6

Figure 4-1 Basic wind speed in miles per hour, 50-year recurrence interval 4-2

Figure 4-2 Wind overturning forces 4-3

Figure 4-3 Wind sliding and bending forces 4-4

Figure 4-4 Wind pressure on roof and eaves 4-4

Figure 4-5 Wind pressure on roof when wall opening occurs 4-5

xvi Coastal Construction Manual

Figure 4-6 Wind pressure on walls when wall opening occurs 4-5

Figure 4-7 Damage from internal pressure 4-6

Figure 4-8 Wind pressure on corner overhangs 4-6

Figure 4-9 Removal of house from foundation piles by wind forces 4-7

Figure 4-10 Waterborne debris deposited against foundation piling 4-8

Figure 4-11 Nearly intact settling of a house when piles lost capacity 4-12

Figure 4-12 Elevating with wood piles 4-13

Figure 4-13 Effect of scour plus wind and water forces on piles 4-14

Figure 4-14 Effect of storm forces on foundation system with

inadequate pile embedment 4-15

Figure 4-15 Pile embedment 4-15

Figure 4-16 Pile embedment using a drop hammer 4-16

Figure 4-17 Square piles set in preaugered holes 4-17

Figure 4-18 Sketch of foundation for house near Malibu Beach, California 4-18

Figure 4-19 Sketch of concrete masonry unit pier 4-19

Figure 4-20 Concrete masonry unit piers supporting reinforced

concrete framing platform 4-19

Figure 4-21 Floor beams bolted to wood piles with metal

straps tying floor joists to floor beams 4-20

Figure 4-22 Pole construction details 4-20

Figure 4-23 Typical pile, floor beam, floor joist arrangement,

showing bolted beam/pile connection and hurricane

clip connections to floor joists 4-21

List of Figures xvii

Figure 4-24 Laminated beam connected to round timber pile

using 1/2-inch steel plate, hot-dipped galvanized after fabrication 4-22

Figure 4-25 Wooden I-beam 4-23

Figure 4-26 Wall sheathing tie from roof to foundation 4-24

Figure 4-27 Corner wood bracing 4-25

Figure 4-28 Gable/overhang failure 4-25

Figure 4-29 Porch overhang damaged by wind uplift 4-26

Figure 4-30 Performance of braced piles at left vs. unbraced piles at right 4-26

Figure 4-31 Performance of braced piles in foreground vs. unbraced piles in background 4-27

Figure 4-32 Effects of Hurricane Frederic's wind and water forces on unbraced pile system 4-27

Figure 4-33 Knee braces 4-28

Figure 4-34 Wood grade beam in both directions 4-28

Figure 4-35 Slab undermined by storm scour 4-29

Figure 4-36 Perimeter grade beam provided additional stability 4-29

Figure 4-37 Slab on grade with thickened edge perimeter grade beam 4-30

Figure 4-38 Double level truss bracing system 4-30

Figure 4-39 Single level truss bracing system 4-31

Figure 4-40 Floor joists insufficiently attached to floor beams by end nailing alone 4-32

Figure 4-41 Metal strap roof anchor 4-33

Figure 4-42 Metal plate roof anchor 4-34

Figure 4-43 Metal hurricane clips 4-36

Figure 4-44 Wood joist anchors 4-36

xviii Coastal Construction Manual

Figure 4-45 Wood joist anchor installation 4-37

Figure 4-46 Double notched spaced beam to pile connection 4-37

Figure 4-47 Connection for built-up beam 4-37

Figure 4-48 Connection at single-notched pile 4-37

Figure 4-49 Spiked grid connection 4-38

Figure 4-50 Mortised gusset connection 4-38

Figure 4-51 Notched pile with gusset 4-38

Figure 4-52 Steel plate insert 4-38

Figure 4-53 Over notched wood pile 4-39

Figure 4-54 Failure of pile connections at floor beam and at knee brace 4-39

Figure 4-55 Steel reinforcing bar inadequate to attach floor beam to this pile 4-39

Figure 4-56 Masonry pier--strap anchor connection 4-40

Figure 4-57 Masonry pier--bolt through beam connection 4-40

Figure 4-58 Masonry pier--beam seat connection 4-40

Figure 4-59 Concrete masonry unit piers connected by galvanized clips to floor beams 4-40

Figure 4-60 Lattice enclosure under elevated structure 4-42

Figure 4-61 Storm damage during Hurricane Alicia 4-42

Figure 4-62 Lattice wall 4-43

Figure 4-63 Wood stud breakaway wall 4-44

Figure 4-64 Light-gauge metal stud breakaway wall 4-45

Figure 4-65 Masonry breakaway wall 4-46

Figure 4-66 a&b Effect of enclosure walls on waves 4-47

Figure 4-67 Pile spacing effect on distribution of wall loads 4-49

List of Figures xix

Figure 4-68 Bracing considerations 4-50

Figure 4-69 Heating/cooling unit elevated to above the BFE 4-52

Figure 4-70 Shutters for window protection 4-53

Figure 4-71 Plywood sheets used for window protection 4-53

Figure 4-72 Loss of roofing in Hurricane Elena 4-55

Figure 4-73 Corrosion of cast iron sewer trap in coastal environment 4-55

Figure 5-1 Typical pile/pile cap/column/grade beam connection 5-2

Figure 5-2 Pile to pile cap connection for high-rise foundations 5-3

Figure 5-3 Skeleton framed building under construction 5-3

Figure 5-4 Typical plan of high-rise building 5-3

Figure 5-5 Typical high-rise shear wall 5-4

Figure 5-6 Shear wall reinforcement 5-5

Figure 5-7 Typical high-rise floor slab section 5-5

Figure 5-8 Typical plan of low- to mid-rise structure 5-6

Figure 5-9 Typical section through low- to mid-rise bearing wall building 5-6

Figure 5-10 Mid-rise residential structure with bearing walls 5-7

Figure 5-11 High-rise structure with poured concrete bearing walls under construction 5-7

Figure 5-12 Two-way floor slab in skeleton framed building 5-8

Figure 5-13 Elevated first floor on high-rise structure, partially enclosed by lattice 5-8

Figure 5-14 Coastal construction with setback requirements 5-9

Figure 6-1 Site plan 6-1

xx Coastal Construction Manual

Figure 6-2 View from beach 6-2

Figure 6-3 Main level plan 6-2

Figure 6-4 Framing plan 6-3

Figure 6-5 Ground level plan 6-4

Figure 6-6 Example I, pile design worksheet 6-5

Figure 6-7 Example I, connection design worksheet 6-9

Figure 6-8 Example 2, pile design worksheet 6-12

Figure 6-9 Example 2, bracing design worksheet 6-16

Figure 6-10 Example 3, pile design worksheet 6-20

Figure A-1 Number of piles required A-1

Figure A-2 Concrete pier cross section A-45

Figure A-3 Grade beams and slabs A-45

Figure B-1 Truss normal to beach B-2

Figure B-2 Exterior diagonal to pile connection B-3

Figure B-3 Interior diagonal to pile connection B-4

Figure B-4 DYWIDAG threadbar diagonal connections B-5

Figure D-1 Water depth relationships D-10

Figure D-2 Resisting force--roof connections D-18

Figure D-3 Resisting force--story connections D-19

LIST OF TABLES xxi

Table 2-1 Saffir-Simpson Hurricane Scale 2-2

Table A-1 Downward Loads per Pile A-4

Table A-2 Horizontal Wind Loads per Pile A-5

Table A-3 Minimum Embedment Depth of Piles A-11

Table A-4 Maximum Unbraced Height of Piles A-13

Table A-4.1 Maximum Unbraced Height of Piles Supporting Breakaway Walls A-20

Table A-5 Uplift Loads per Foot of Wall A-21

Table A-6 Uplift Loads per Pile A-35

Table A-7 Capacity per Bolt of Floor Beam Connections A-42

Table A-8 Concrete Masonry Unit Piers A-43

Table A-9 Concrete Piers A-44

Table A-10 Fastener Capacities in Shear A-46

Table A-11 Fastener Schedule for Breakaway Walls A-47

Table B-1 Horizontal Water Loads per Pile B-7

Table B-2 Loads on Transverse Truss Members B-14

Table B-3 Allowable Loads for Single 2-by-8 Diagonals B-15

Table B-4 Allowable Loads for Single 3-by-8 Diagonals B-15

Table B-5 Allowable Strut Loads B-15

Table F-1 Pile Costs F-2

Table F-2 Costs for Components of Pile Foundations F-3

Table F-3 Costs for Piers and Shear Wall Foundations F-5

Table F-4 Costs for Other Components of Elevated Construction F-6

Table F-5 Breakaway Wall Costs F-7

Table F-6 Elevation Costs for 28-by-32-foot House F-8

Introduction 1-1

Chapter 1

INTRODUCTION

1.1 PURPOSE AND SCOPE

This manual provides guidance for the design andconstruction of coastal residential structures able to resistdamage from flood, wind, and erosion hazards. Includedherein are discussions of new residential structures--principallydetached single-family, attached single-family (townhouse),and low-rise (three-story or less) multifamily houses.Nonresidential structures of similar sizes, loads, andconstruction can also be considered by interpreting the dataand procedures found in this manual, as can retrofitting ofexisting structures.

This introductory chapter is followed by a generaldescription in Chapter 2 of the coastal regions of the UnitedStates, weather conditions, some current constructionpractices, and generalized shoreline constructionconsiderations. Chapter 3 presents general information andrecommendations on site design. Chapter 4 constitutes amajor portion of the manual; it describes forces to be resisted,materials used, and many design and construction details. Adiscussion of application of these coastal constructionconcepts to larger structures is provided in Chapter 5. Designprocedures and worked design examples are presented inChapter 6 to demonstrate the use of the design tables in theappendices. The appendices present the design data tables,bracing details, detailed design equations and procedures,computer program listings, construction cost information, asample coastal construction ode, references, individualscontacted in researching this manual, and other pertinentinformation.

This manual will be of assistance primarily to persons inconstruction of modest (one- and two-story) residentialstructures (and similar-sized nonresidential structures) incoastal areas of the United States. Individual home owners,building contractors, and architects or engineers can all applythe information presented in this design manual. Using thedata included herein, a design professional may extrapolate forresidential (or nonresidential) structures slightly larger than theone- and two-story houses considered in the design equations,charts, and tables and described in the example solutions.

The construction details, design procedures, and chartsin this manual are based upon a comprehensive evaluation ofmany existing beach houses, current construction practicesalong U.S. coastlines, and various building codes applicable tocoastal construction. Practical designs of modest cost andconstruction details are presented to provide for storm-resistantresidential structures.

Examination of both damaged homes (Figure 1-1) andstorm-resistant structures along the Atlantic and gulf coasts hasdemonstrated the desirability of some of the constructiondetails included herein. On the Atlantic coast, public officials,architects, engineers, and builders from Massachusetts to theFlorida Keys were interviewed. They contributed ideas,comments, and recommendations on construction in coastalhigh hazard areas. Similar information was gathered fromFlorida to Texas along the gulf coast, California for the Pacificcoast. This manual presents a composite of recommendedand required construction details for the entire U.S. coastline.

Much information was obtained by evaluating thedamage in Alabama caused by Hurricane Frederic inSeptember 1979; Hurricane Alicia, which hit the Texas gulfcoast in August 1983; Hurricane Elena, which hit the gulf coastin Florida to eastern Texas in September 1985; and

1-2 Coastal Construction Manual

Figure 1-1. Home damaged by winds during Hurricane Elena.

Hurricane Gloria, which in late September 1985 affected theentire east coast before coming ashore on Long Island.Firsthand investigations of the aftermaths of these storms,together with other accounts of storm effects, investigations ofcurrent practice, and personal site visits contributed to thematerial contained in the manual.

Only modest variations in construction practice werefound from one geographic location to another. However, forareas subject to higher winds and waves, special attention toerosion and scour is necessary to ensure sufficient lateralsupport to the foundations. Construction details such as gradebeams have been "borrowed" from certain geographic areas tohandle this problem. Similarly, foundation bracing issuggested for use in many coastal areas where additionalstrength is required due to high wind and wave forces. Whenstructures are elevated more

to 12 feet above grade, a more substantial bracing system isnecessary. A system of trusses built between the elevatingpiles or poles is recommended to resist lateral forces from windand waves.

1.2 NATIONAL FLOOD INSURANCE PROGRAM

Initiated by Congress in 1968, broadened andstrengthened by amendments in 1969, 1971, and 1973, theNational Flood Insurance Program (NFIP) is designed to fulfillone essential purpose: flood hazard mitigation through theamount of property exposed to damage from flooding. Theprogram is administered by the Federal InsuranceAdministration (FIA) of the Federal Emergency ManagementAgency (FEMA), and its scope includes all communitiesidentified by FIA as containing flood hazard areas. To datemore than 17,500 communities have been so identified, of theapproximately 22,000 estimated to contain such areas.

The NFIP is based on the dual principles of making floodinsurance available to property owners in flood-prone areas,and of requiring sound flood plain management in flood-pronecommunities. As long as the community elects to participate inthe program, the program offers flood insurance protection forbuildings and their contents located in the community.

In return for making flood insurance available, the NFIPrequires affected communities to prudently regulate newconstruction and development in special flood hazard areas.These areas include all land inundated by the flood that has a1 percent chance of being equalled or exceeded in any givenyear. This event is known as the "base flood" or "100 yearflood" and is used by virtually every Federal agency in theadministration of programs related to flood plains. In addition,this same standard is required, either by

Introduction 1-3

law or regulation, in many states and is used administratively inthe operations of virtually every state's programs dealing withthe use of flood plains.

1.2.1 Emergency Program

The NFIP is administered in two phases: the EmergencyProgram and the Regular Program.

The function of the Emergency Program is to make floodinsurance readily available to property owners throughoutflood-prone communities. The operation of the program issimple and direct. FEMA notifies a community that it has beenidentified as flood prone by providing the community with aFlood Hazard Boundary Map (FHBM). Prepared from the bestavailable data, this map is a preliminary delineation of specialflood hazard areas within the community. A communityreceiving such a map may participate in the program bycompleting an application to FEMA. Upon approval of theapplication, limited amounts of Federally subsidized insurancebecome available in that community.

The limits of coverage for the initial or first-layerinsurance protection available under the Emergency Programare $35,000 for single-family structures and $100,000 for allother residential and nonresidential structures. Coverage forthe contents of structures may also be purchased. Up to$10,000 per unit may be purchased for residential structuresand up to $100,000 per unit may be purchased fornonresidential structures.

1.2.2 Regular Program

Once a community has qualified for the Emergency Phase ofthe NFIP and insurance protection is available, an

extensive technical Flood Insurance Study of the flood hazardsin the community is conducted by an engineering contractorfor FEMA. This detailed study includes development of aFlood Insurance Rate Map (FIRM) and is conducted at no costto the community. The flood elevations derived from this studyand the resulting FIRM are the basis on which the insurancerates for the community are established and specific flood plainmanagement regulations formulated. Once a communityadopts the appropriate flood plain management regulations,the community enters the Regular Program and additionalflood insurance coverage becomes available, but at actuarialrates. These rates, based on the severity of the flood hazard,are charged for additional or second-layer coverage forexisting structures and for all coverage for new structures. Newconstruction is that which is started after the effective date ofthe FIRM or December 31,1974, whichever is later.

1.2.3 Plain Management

The specific flood plain management regulations thatmust be adopted depend to some degree upon the datadeveloped in the detailed insurance study and provided to thecommunity by FEMA. Therefore, these regulations may beadopted incrementally by the community as the necessary databecome available. For example, throughout the EmergencyProgram the community is required to apply minimal flood plainmanagement regulations based on the FHBM and is requiredto use reasonably any additional data that may be availablefrom other sources to establish the flood elevations.

However, after the Base Flood Elevations (BFE's) andFIRM are available from FEMA, the community must adoptregulations that will protect any new construction frominundation during the 100 year flood.


FIRM's prepared for coastal communities depict the 100year coastal flood plain and the elevations of the 100 yearflood. On this type of FIRM, the 100 year coastal flood plain isdivided into two adjacent zones that define the differentdegrees of hazard present, and thus require different floodplain management techniques to satisfy the damage reductionrequirements of the NFIP. The V zone (velocity zone) is thatportion of the coastal 100 year flood plain that would beinundated by tidal surges with velocity wave action. Generally,the V zone indicates the inland extent of a 3-foot breakingwave, where the stillwater depth during the 100 year flooddecreases to less than 4 feet.

The A zone is that portion of the 100 year flood plain notsubject to wave action. However, the residual forwardmomentum of the breaking wave may be present in this zone.

1.2.4 V Zones

The minimum requirements for construction in V zonesdiffer significantly from the minimum requirements forconstruction in coastal A zones. In V zones, all newconstruction and substantial improvements to existingstructures must be elevated on adequately anchored pilings orcolumns so that the bottom of the lowest horizontal structuralmembers of the lowest floor (excluding the pilings andcolumns) is at or above the BFE. A registered professionalengineer or architect must certify that the structure is securelyfastened to adequately anchored pilings or columns towithstand velocity waters and hurricane wave wash forces. Inaddition, the space below the lowest floor may be used solelyfor parking of vehicles, building access, or storage and mustbe free of obstructions, or may be enclosed with nonsupportingbreakaway walls, open wood lattice work, or insect

screening intended to collapse under wind and water loadswithout damaging the elevated portion of the building or thefoundation.

FIRM's published for coastal communities include BFE’sthat incorporate wave heights or wave runup associated withthe 100 year flood. Due to differing shoreline conditions,FIRM's for east coast and gulf coast communities include waveheights in BFE's, while FIRM's for west coast communitiesinclude wave runup. Use of this manual is unaffected by whichwave characteristic was used for the applicable FIRM, and theterm wave height is generically used.

Additional NFIP standards for V zones require that fill notbe used for the structural support of new or substantiallyimproved structures, and that sand dunes and mangrovestands may not be altered so as to increase the potential forflood damage.

1.2.5 A Zones

In coastal A zones, the FIRM identifies the appropriate100 year flood elevation. The A zone is that portion of the 100year coastal flood plain subject to wave action of lesserseverity. It is important to note that because of momentum ofbreaking waves, water may be moving at high velocities in thiszone, especially in the vicinity of the V zone/A zone interface.

At a minimum, new construction or substantial im-provements of residential structures in coastal A zones must beelevated so that the lowest floor (including basements) is at orabove the BFE. This elevation may be accomplished throughuse of fill, raised foundations, or piles or columns.

Introduction 1-5

1.3 BUILDING CODES

FEMA's NFIP regulations and building coderequirements are essentially parallel efforts, both with thepurpose of providing well constructed and safe housing.Because of its more specialized interests, FEMA has initiatedactions relating to construction improvements in flood proneareas, and is continuing to work with code groups and otherinterested parties. These actions include efforts to ensurecompatibility between NFIP regulations and guidelines andcode provisions (e.g., BOCA, Standard, and Uniform Codes),and updating of publications such as this Coastal Construction Manual and the Elevated Residential Structures manual.

Historically, building codes were developedindependently by communities to meet their specific needs.Although many communities, and some states, continue tohave their own codes, most have now chosen to adopt (withamendments) one of the three model building codes (Standard(Southern Building Code Congress International, Inc., 1982);BOCA (Building Officials and Code AdministratorsInternational, Inc., 1984); and Uniform (International Congressof Building Officials, 1984)). Each of these model codes haslanguage and provisions suitable to large regions of thecountry--the Standard Code being in common use in theSouth, the BOCA Code in the Midwest and East, and theUniform Code in the West. The model codes have beenextensively revised over the years to reflect new constructionmaterials and techniques, changing government regulations,and increasing awareness in such areas as seismic-resistantdesign and energy conservation.

Coastal construction codes have been adopted at thestate and local levels. Other states, in recognizing the needs ofcoastal communities and counties for guidance in this area,have made available coastal code language for adoption bylocal jurisdictions. Appendix G to this manual provides asample coastal construction code that may be adopted, withmodifications as appropriate, by jurisdictions for whom state orother regional guidance has yet to be provided.

Coastal Environment 2-1

Chapter 2COASTAL ENVIRONMENT

Coastal design and construction are affected by anumber of natural and man-influenced factors. These includethe physiography, weather, development patterns, andconstruction practices for a given coastal regime. This chapterprovides a general overview of these factors and theirrelationship to or influence on residential construction incoastal high hazard areas.

Coastal considerations in dwelling development mainlyinvolve the dynamic beach response to wave energy and waterlevels. Long-term beach processes are beyond the scope ofthis manual, but they form an important design checkpoint.Many of our shorelines are moving or naturally eroding, andman's actions to resist or alter these processes must beundertaken with recognition of both the complexity of theinterrelationships and the tremendous energies involved.Erosion of the shore can occur when material supply isreduced and the dynamic beach profile is disrupted. Sucherosion is frequently caused when the area between thesource of littoral sand and the site under study is disrupted.Such alterations include:

• Damming of waterways that previously carried streamerosion material to the shoreline.

• Building of offshore structures such as breakwaters,

jetties, and groins.

• Dredging of offshore channels.

Long-term, gradual shoreline loss and short-term, storm-induced scour and erosion are both significant factors to beconsidered when selecting and building on a coastal site.Long-term erosion rates of 1 to 2 feet per

year are common along sandy shorelines, and even greaterrates are experienced in areas such as tidal inlets. These long-term effects have a variety of causes, including the presentgradual raising of ocean levels due to climatic warming, anddynamic beach processes such as alongshore transport ofsand and the accumulation of sand in tidal inlets, capes, jetties,and various other natural and manmade shoreline features(Rogers, 1982). There is concern that the rising sea level isdeveloping from long-range global climatic changes, that it ispermanent, not cyclic, and due (or at least related) to what isknown as the greenhouse effect. Long-term planning mayneed to consider permanent sea level rise. The sedimentbudget and coastal processes in an area should be analyzedto establish historical shoreline behavior patterns anddetermine housing setback distances.

Short-term erosion and scour at a site can be dramaticover the course of a single storm or storm season. Onceexposed by erosion, bulkheads, pilings, and other manmadestructures are increasingly attacked by wave action andseveral feet of scour can occur. Experience has generallyshown that it is best to locate structures well away from erodingbeaches to avoid the effects of erosion the structure's expectedlifetime. Where this is infeasible, foundations should bedesigned for the anticipated erosion, rather than relying uponerosion control structures such as seawalls, bulkheads, or rockrevetments. Erosion control structures should be built only inareas where protection from an imminent hazard is required.

An assessment of the erosion and storm damage potential ata site can be based on historical and other informationavailable through state coastal zone management agencies,the Corps of Engineers, and state universities. Advisoryservices such as Sea Grant, the county extension office, andthe Soil Conservation Service are good sources and also havepersonnel familiar with


specific local conditions. Long-term residents should not beoverlooked as sources of historical flooding and damageinformation.

Many of the above-named organizations have publishedinformation available to assist the siting and construction ofcoastal structures. The most inclusive and comprehensivesource to date is the "Living With The Shore" series by DukeUniversity Press, which when completed will include more than20 books covering the Atlantic, Pacific, and Great Lakesshorelines.

Beach profile response to storm activity over a shortperiod should be considered. Principal design criteria includebeach profile shape, probable storm surge, and incident wavecharacteristics. Flat beaches signify little storm erosion andrelatively slight storm wave action due to the energy-dissipation effect over the flat slope. Steep profiles are usuallyassociated with coarse beach sands and indicate an areasubject to more severe wave attack. Furthermore, a steeperbeach slope to backshore dunes promotes accelerated erosionrates, particularly during periods of abnormally high tide; sucha situation warrants increased setback distances. Generally,fine beach material and flat beaches are indicative of lesserosion and wave force, while coarse sand and steep beachslopes indicate more forceful erosion and wave action.However, significant erosion can be expected to occur underhurricane conditions even on flat beach slopes.

A beach is constantly in a state of dynamic flux,characterized by two modes of transport: littoral driftalongshore and onshore-offshore movement. Incident waveenergy usually breaks onshore at a slight angle to theshoreline, which results in a net component of energy alongthe coast depending on the wave direction. This combination ofbreaking waves and angular attack can transport considerableamounts of sand alongshore.

Seasonal beach profile changes from erosion and accretionare associated with the incident wave's height, period, andshape characteristics. Short-period plunging storm waveserode beaches, and longer-period prevailing spilling-typewaves cause accretion of foreshore and backshore areas. Thewidth of the beach berm and extent and dimensions ofbackshore dunes determine the amount of natural stormprotection available to coastal dwellings.

To summarize, the particular beach characteristics, thestorm and surge history, and the beach profile response tothese factors determine desirable location and design ofdwelling units and their susceptibility to water level and waveattack. In other words, it is more effective and less costly todesign so as to work with nature rather than trying to fight it.

For the purpose of characterizing some of the severe tostorms to which the U.S. coastline is subject, the Saffir-Simpson Hurricane Scale is presented in Table 2-1. Thisscale is used by the National Weather Service to give publicsafety officials a continuing assessment of the potential forwind and storm-surge damage from a hurricane in progress.

TABLE 2-1SAFFIR-SIMPSON HURRICANE SCALE

Scale No. Winds Storm-Surge Potential (Category) (mph) (ft) Damage

1 74-95 4-5 Minimal2 96-110 6-8 Moderate3 111-130 9-12 Extensive4 131-155 13-18 Extreme5 >155 >18 Catastrophic

A number of studies of tropical cyclones, includinghurricanes, have been made by the National Oceanic and


Atmospheric Administration (NOAA). In one study for theperiod 1886-1970 (Simpson and Lawrence, 1971), tropicalcyclones are divided into three categories. One categoryincludes all cyclones whose maximum (reported) sustainedwinds were 40 mph (gale force) or higher; the second, includestropical cyclones with reported winds of 74 mph (hurricaneforce) or higher; the third category "great hurricanes,"characterizes storms with sustained winds of 125 mph or more.Based on these data, areas with a high probability ofhurricanes (Figure 2-1) were identified, based on observedpast storm occurrences. Sectors not experiencing a "greathurricane" during the period of study are not immune.

For discussion purposes, the coastline of the contiguous48 states and Hawaii was divided into six regions and datawere collected on historical and current construction practices.Information presented in this manual should be applicable toalmost all coastal areas of the United States. Each region hasunique general shoreline features, development patterns, andits own storm history. This regionalization serves an additionalpurpose of providing convenient geographic segments fordiscussion. Construction and design considerations for Hawaiiare not fully included in this document, though a limited amountof information is provided. The designated regions are listedbelow and are based on the coastal classification scheme ofTerrell (1979):

• North Atlantic Coast , the Maine-Canada border southto Cape Cod.

• Middle Atlantic Coast , Cape Cod south to the

Virginia-North Carolina border. • South Atlantic Coast , the Virginia-North Carolina

border south to the southern tip of Florida.

• Gulf Coast , the southern tip of Florida west to Mexico.

• Pacific Coast , the California-Mexico border north tothe Washington-Canada border.

• Hawaiian Coast , the entire coastline of the Hawaiian

Islands.

General descriptions of these differing coastalenvironments follow. Locations referenced in the text areshown on Figure 2-2.

2.1 NORTH ATLANTIC COAST

The North Atlantic region comprises two generalsegments in New England, characterized by their differences interrain and residential development. The natural divisionbetween these two areas is Cape Elizabeth, Maine.

From the Maine-Canada border to Cape Elizabeth thecoastline is rocky, steep, and deeply incised with numerousbays, estuaries, and islands. There are small areas of mudflat,marshes, and shallow areas but generally the coast is of highenergy and experiences high tidal ranges. South of CapeElizabeth to Cape Cod, the shoreline grades from rocky tosandy, especially south of Cape Ann. Beaches are generally ofhigh energy.

The southern portion of the North Atlantic coastline,through Massachusetts, is heavily populated andextensively developed. This portion of the coastline alsocontains many older structures, some of which date from thenineteenth century. Both the mainland and the barrier beacheshave been developed. Because of the desirability of theproperties involved, very small lots with minimal setbacks andlittle space between residences have resulted.


Figure 2-1. Hurricane experience of eastern United States, 1886 to 1970.

Many residences have been winterized and are inhabitedyear-round.

The northern portion of the area is much less developed,consisting primarily of rugged terrain, scattered resortresidences, rural areas, and fishing villages. Where structuresare present, ocean and side yard setbacks are again minimaland there is a tendency toward crowding. The northern portionis much less susceptible to large seasonal influxes ofpopulation than the southern portion.

Much of the development in both the northern andsouthern portions of this region either predates constructioncodes or was constructed under codes with few specificprovisions for coastal construction.

The northern New England area experiences amoderate to severe climate, suffering from increasingly harsherwinters toward the north. Generally, north of Cape Cod,Massachusetts, the northeaster is the most damaging eventand controls design. These are relatively slow moving storms,with large amounts of precipitation and high winds, and areprimary cause of coastal flooding erosion. Hurricanes are notas severe a threat as these winter storms.

In general, the Massachusetts coastal area has acontinuous fluctuation in weather elements due to its northernlatitude and the fact that it is situated in a path followed by low-pressure systems. Statistics developed by the U.S. ArmyCorps of Engineers in Boston indicate that over the past 50-year period, three or four northeaster-type storms haveoccurred during each month between November and March.These generally cause at least some damage, such asshingles and shutters being blown away. Hurricanes in 1938and 1954 as well as northeasters in 1972 and 1978 severelyaffected the area.


Figure 2-2. The United States coastline.


2.2 MIDDLE ATLANTIC COAST

The Middle Atlantic Region also comprises two generalsegments characterized by their differences in terrain anddevelopment; the natural division is Montauk Point. Thecoastline from Cape Cod to Montauk Point, including LongIsland Sound, is fairly irregular with several large islands, bays,and sounds. The beaches are mainly sandy and are variouslycharacterized by high energy areas, marshy areas, barrierislands, and dunes.

From Montauk Point to the Virginia-North Carolinaborder, the coastline contains wide, sandy, high energybeaches. Extensive marsh areas are protected by a series ofbarrier islands with dune systems. Estuaries of varying sizes,including Chesapeake Bay and Delaware Bay, are foundthroughout this portion of the coast.

Development between Cape Cod and Montauk Point issimilar to that described above for the southern portion of theNorth Atlantic coastline. The coastline south of Montauk Pointis characterized by resort towns, summer residencecommunities, and state and Federal park lands and refuges. Inseveral areas, primarily near the mouths of major bays andrivers, harbors have been developed that have fosteredconsiderable growth. Such population centers include NewYork City, at the mouth of the Hudson River, and the HamptonRoads, Virginia, area at the mouth of Chesapeake Bay.Between these population centers, the coastline has adistinctly rural character, with summer tourism the primarycommerce. Much of the land on which resort towns havedeveloped consists of barrier beaches.

Although nineteenth-century structures are at the core ofmost of the towns, a large amount of construction began afterWorld War II and continues to date. Present-day construction isprimarily high-rise apartments and subdivision developments.Generally, lot sizes are larger

than those in New England; side yard and especiallyoceanside setbacks have long been in force, resulting in muchless crowded communities than farther north.

In New Jersey and New England, the U.S. Army Corpsof Engineers and some municipalities have attempted to haltthe landward advance of the ocean with seawalls. Suchdefenses have not been particularly effective. In theundeveloped coastal areas of Maryland and Delaware,oceanside setbacks and the preservation of dunes havegenerally prevented shoreline deterioration. In developedareas, however, municipalities and the Corps of Engineershave attempted to stem the littoral drift and erosion of thebeaches by constructing groins and jetties, and somehomeowners have built individual bulkheads.

The Middle Atlantic States coastline has historicallybeen subjected to numerous coastal storms severe enough toinflict significant property damage. This region averages twoto three winter storms each year and an occasional hurricane.The hurricane controls design along this reach of coastline. Asevere storm in 1962 caused damage along the Middle Atlanticcoast comparable to that inflicted by the February 1978northeaster in Massachusetts.

The 1962 storm caused major damage to numerousstructures, resulting in revised building codes andconstruction techniques. Because a major portion of thestructures in this area received some damage in 1962, newerconstruction incorporates design and construction techniquesthat can better resist storm damage. The performance of thesenewer techniques in less severe recent storms has beensubstantially better than in 1962. Performance has also beenimproved in much of this area by restricting developmentthrough setback regulations.

The Middle Atlantic States received a close call fromHurricane Gloria in September 1985. Gloria had reached


winds of over 150 mph as it approached the United States fromthe Caribbean; these winds had diminished only to 130 mph asthe storm skirted Cape Hatteras, North Carolina. The stormremained offshore, missing the Maryland, Delaware, and NewJersey coasts, finally coming ashore on Long Island. Hitting atlow tide with 100 mph winds, the storm damaged severalcommunities, including Fire Island, before passing intoConnecticut. For all its potential, Hurricane Gloria did onlymodest damage, while providing valuable lessons inemergency preparedness and evacuation planning.

2.3 SOUTH ATLANTIC COAST

The South Atlantic coastline comprises three generalsegments: the Outer Banks from the Virginia-North Carolinaborder to Cape Fear, the coastline and Sea Islands from CapeFear to St. Johns River, and East Florida from St. Johns Riverto the southern tip of Florida. The Outer Banks reach containsnumerous long, narrow barrier islands characterized byrelatively steep, broad quartz sand beaches as shown onFigure 2-3. These islands protect large landward soundcomplexes and front against a turbulent, high energy sea.

The Sea Islands comprise numerous, irregularlyshaped small barrier islands that contain wide, low-slopedquartz sand beaches. In many areas, the difference in width ofbeach between high and low tide often exceeds 300 feet.Behind the islands are expansive tide marshes that are highlydissected by coastal plain rivers and distributaries. The barrierislands of the East Florida segment are long and narrow, andgenerally front high-salinity lagoons. The beaches are low-lying and composed of calcareous sands. In the southernportion of the Florida mainland, the continental shelf is narrowand high-relief coral reefs dominate the nearshore area.Limestone underlying the Florida mainland extends furthersouth in an

undersea ridge that forms the Florida Keys, a chain of 97 low-lying islands. The average ground elevation in the Keys isabout 3 feet above sea level, and only a thin soil cover overliesthe limestone in most areas.

Figure 2-3. Representative beach profiles.

The South Atlantic region has a temperate climate that issubject to the effects of coastal storms and occasionalhurricanes that produce high winds, above-normal tides, andheavy rains. The most frequent storm types are winter cyclonicstorms travelling northeastward up the coast. These averagefrom eight to ten storms per year, many of which, according tolocal residents, cause minor damage to residences and erodeappreciable amounts of beach. Hurricanes, while lessfrequent, are the major cause of damage to residentialstructures and thus are the controlling factor in design. Thearea is vulnerable to tidal flooding, but tides greater than +8feet mean low water (mlw) are rare; the highest recorded tidelevel was 11.2 feet mlw, in August of 1893.


The Outer Banks of North Carolina, the coast near theSouth Carolina-Georgia border, and the east coast of Floridaare the areas within the South Atlantic region most likely to bestruck by a hurricane. National building codes present theirhighest coastal design wind speeds for the Outer Banks andsouthern Florida.

Along this coastline, numerous resort developmentshave been created within the past 15 to 20 years in areaswhere there had been little or no development. Thus, anincreasing number of residences are being constructed thatare susceptible to coastal flooding damage. Hurricane Hazelstruck the North Carolina coast in 1954, prior to the era oflarge-scale coastal development. During that storm, mostbuildings on the barrier islands were destroyed by waves andstorm surge. In 1984, 30 years later, Hurricane Diana madelandfall on the North Carolina coast with sustained winds of104 mph and gusts greater than 115 mph. However, only 2 to4 percent of the existing buildings were damaged. Mostdamage was minor (porches and overhangs) and only 10buildings were judged to be total losses. Major causes werenot waves, erosion, or storm surge, but high winds (Rogers,1985).

Most construction techniques now in use were derivedfollowing Hurricane Hazel in 1954 and after the accelerateddevelopment of the coastline of North Carolina and SouthCarolina. Recent state and local controls are in effect and haveimproved the quality of construction throughout this area.These improvements can be attributed to two primary factors.First, many areas are being developed as relatively exclusiveresort communities, leading to more expensive housing andmore local controls, such as architectural review boards. Theboards contribute to the control of natural vegetation, duneprotection, height and view restrictions, public access tobeaches, and a higher general quality of construction. Inaddition, the fact that these residences are usually

engineer- or architect-designed custom homes contributes tomore carefully detailed joints and closer controls during theconstruction process.

The ability of local building officials to interpret andenforce the requirements for construction has also had aneffect on quality. Some jurisdictions have upgraded theauthority and professional status of their building officials. Themore strict building departments have been able to betterensure better structures; loosely interpreted standards allow alower quality of construction.

Much of Florida's recent coastal development is high-density construction such as hotels, high-rise apartments, andcommercial facilities (see Chapter 5). However, there arecoastal subdivisions not fully developed, some land subject tosubdivision, and isolated building lots in Florida's coastal highhazard areas. The State of Florida and local jurisdictions havealso made substantial efforts to upgrade the quality of coastalconstruction and inspection. One such effort is the adoption byFlorida of a Coastal Control Line, with the State limitingconstruction seaward of the line.

2.4 GULF COAST

The gulf coast is routinely a target for hurricane activity,and the area exhibits some of the highest probabilities oftropical storm occurrence in the country. Within this region,there are eight segments that can be characterized by theirdifferences in physiography. Each exhibits varying conditionsthat determine susceptibility to storm-generated erosion, waveaction, and tides.

From Key West to Cape Romano the low relief coastlineis dominated by a multitude of small mangrove islands, tidalchannels, and extensive swamps. The continental shelf isvery broad, extending over 800 miles


offshore. Human development is minimal due to thepredominance of the Everglades. From Cape Romano toTarpon Springs, a transition occurs from a mangrove-dominated coastline to sandy beaches and marshy bayscharacteristic of the northern Gulf of Mexico. Exposed sandybeaches with scattered mangrove stands and rocky areas arepredominant shoreline features along a series of barrierislands protecting marshy embayments. The continental shelfis broad and regular.

Continuing north to Lighthouse Point, the shoreline ofthe Florida Big Bend is rugged and characterized by rockybottoms, very wide shallow areas, and extensive seagrassbeds, oyster bars, and marshes. The region surrounding theApalachicola Delta to Cape San BIas has an exposedcoastline partially protected by barrier islands and smoothsandy beaches; protected bays are turbid with muddy bottoms.From Cape San BIas to Petit Bois Pass, Alabama, the coastcomprises high energy sand beaches and an extensive systemof dunes and barrier islands. The shoreline is relatively steepand the dunes rise sharply.

The Mississippi Delta, extending from Petit Bois Passwest to Vermilion Bay, is characterized by an extensive andwide marsh and barrier island system. The marshes containmany lakes and bayous and are crossed by numerous streamchannels. From Vermilion Boy to Galveston Bay, the coast isidentified as a strandplain-chenier complex. The shoreline isexposed without substantial barrier islands and ischaracterized by a marshy plain with a series of long, low,narrow brushy beach ridges that lie parallel to the coastline.The Texas barrier island system extends from Galveston Bay tothe United States-Mexico border. This low-relief section ischaracterized by an extensive lagoon system bordered bylong, narrow, sandy barrier islands. On the upper portion, toCorpus Christi, marshes are common in the bays. The bays ofthe southern portion have minimal freshwater inflow;hypersaline

conditions predominate and submerged grass beds arecommon.

Development along the gulf coast is quite variable.Many areas, because of the inhospitable terrain or shorelineprotection (refuges and parks) are relatively undeveloped.These include much of the Texas barrier island system, thechenier plain, the Mississippi Delta, the Florida Big Bend, andthe mangrove swamps of southwest Florida. Development inthese areas usually occurs on the mainland behind the barrierislands (e.g., Corpus Christi, Texas) or on the landward side ofextensive marsh systems (e.g., Lake Charles, Louisiana). Anotable exception is Galveston, Texas, which is built directly ona barrier island.

On the other hand, the central Florida coast, thepanhandle of Florida, and coastal Alabama and Mississippi arehighly developed with beach communities and resorts.Building has occurred both on the barrier islands and on themainland, although the bigger cities such as St. Petersburgand Pensacola tend to be on the mainland, while resorts arelocated on the barrier islands.

A wide range of housing types is found along the gulfcoast. Older structures abound on the gulf; however, asignificant amount of recent construction has taken place thatexhibits familiarity with current construction technology,particularly with regard to elevated structures.

Two gulf coast areas can be distinctly identified ashaving high hurricane probability. These are the areas aroundGalveston, Texas, and Pensacola, Florida. Other areas alsoappear to be prone to hurricane activity, specifically, the areaaround the Florida Keys and the area south of New Orleansnear Grand Isle, Louisiana.

The Florida Panhandle has a moderate climate that isoccasionally influenced by hurricanes. There have been


nine seriously destructive hurricanes since 1879, the worst inSeptember 1879 and September 1926. The area fromPensacoIa, Florida, to Pascagoula, Mississippi, has alsoexperienced relatively frequent hurricane damage. Millionsof dollars of property damage in the Pensacola-Panama City,Florida, area resulted when Hurricane Eloise passed throughthe area in 1975. The heaviest damage was due to erosion(scour) and occurred primarily to residences with slab-on-grade first floors and other nonelevated structures thatdepended on shallow footings for structural stability. Thebeach profile, with its steeper slope and higher dune system, isextremely susceptible to dune toe erosion and rapid duneretreat during a short duration storm. Figure 2-4 shows a slab-on-grade house on Santa Rosa Island, Florida, that wasundermined in a storm and is a total loss. Erosion has alsoundermined the short post foundations supporting the porch onthe house in the foreground.

In September of 1979, Hurricane Frederic didextensive damage to the Gulf Shores-Mobile, Alabama, areas(Figures 2-5 and 2-6). Maximum sustained winds on land wereestimated at over 110 mph, with highest gusts reported at 145mph. The peak storm surge of 12 feet at Gulf Shores, Alabama,destroyed much of the island, while an 11-foot surge atDauphin Island destroyed the causeway connecting the islandto the mainland. The estimated damage total of $2.3 billionmakes Frederic the second most costly U.S. hurricane inhistory.

Coastal areas near the Mississippi-Alabama borderwere hit again in September 1985 by Hurricane Elena. Initiallyprojected to come ashore near Cedar Key in Florida, Elenastalled for several days before moving westward, finally makinglandfall in the Gulfport-Biloxi, Mississippi, area. Locations eastof the landfall received the most damage, primarily from wind,although many

homes sited at the water's edge were damaged by waves,erosion, and debris as well. Considerable wind damage wasreported, from loss of roofs, roof overhangs, porches, andwindows broken by flying debris.

Figure 2-4. Undermining of shallow supported foundations bybeach erosion.


Figure 2-5. Contrasting minor and major damage to twoadjacent houses during Hurricane Frederic.

The southern portion of the Texas coast has a marineclimate that is subject to major tropical storms and hurricanes.Six hurricanes have occurred in the area since 1900; one ofthese, in 1900, completely destroyed the City of Galveston.Other damaging hurricanes have included Debra in 1959,Carla in 1961, and Alicia in 1983. The City of Galveston, andGalveston Island in particular, have frequently receivedhurricane and storm damage. Storms causing high waves andsevere beach erosion occur almost annually on GalvestonIsland. Because of exposure along both the gulf coast andGalveston Bay, significant damage due to storm surge andwave action has occurred in the past and could occur again.Some protection has been provided through construction of theGalveston reentrant

Figure 2-6. U-shaped structure damaged by Hurricane Frederic.

seawall by the U.S. Army Corps of Engineers. Long termerosion is, however, a problem in this area and is common atboth ends of the Galveston seawall.

Hurricane Alicia in August 1983 was the costliesthurricane in U.S. history, mainly because its path included thepopulated areas of Galveston and Houston on the Texas gulfcoast. Damage was estimated at as much as $3 billion; inGalveston County, damage was estimated at $100 million.Alicia severely damaged nearly 1,000 homes, and more than100,000 claims for property damage were filed with insurancecompanies. Several houses on Galveston Beach weredestroyed due to inadequate pile embedment and scour anderosion. The majority of


damage, however, was caused by inadequate wind anchoring,with resultant loss of roofs and collapsing of walls.

Because of the continual threat of hurricanes and severestorms along the gulf coast, builders, designers, engineers,and building officials in this area are generally familiar withelevated structures and storm-resistant constructiontechniques. Application of such techniques is much inevidence, particularly in new construction.

2.5 PACIFIC COAST

The Pacific coast is composed of two basic segments:the southern California coast from the U.S.-Mexican border toPoint Conception and the coasts of California, Oregon, andWashington from Point Conception to the U.S.-Canadianborder.

The southern segment is characterized by a fairlysmooth coastline with long stretches of sandy beachesinterspersed with rocky headlands. Both low and high cliffsborder the landward side of the beaches while a few largeislands occur offshore; nearshore algae and kelp beds arewidespread.

The northern segment has mainly rocky, high-cliffedbeaches with numerous pocket beaches. North to CapeMendocino, extensive algal communities and kelp beds arepresent. From Cape Mendocino to the Canadian border, thecoastline is moderately dissected with numerous rocky islands,small bays, and estuaries with mudflats and eelgrass beds.

Although not subject to the same frequency of highstorm waves from major storms and hurricanes as the Atlanticand gulf coasts, the Pacific coast experiences occasionaltropical cyclones and tsunamis. Some of these storms originatenear Japan and grow as they track across

the Pacific. In addition, tropical cyclones that form off theMexican coast occasionally travel north and affect southernCalifornia. Tsunami activity has also been recorded; the mostdamaging was in 1964, at Crescent City, California.

Storm surges are of limited magnitude on the Pacificcoast because of the great ocean depths close to shore.Numerous hurricanes form off the west coast of Mexico, butthese tend to move seaward. Only rarely does one of thesehurricanes reach the extreme southern California coast, andthose that do are weak compared to east coast hurricanes.Their intensity is limited by the cold temperature of theunderlying water surface and other factors. The hazardscontrolling design for residential buildings along the Pacificcoast are storm waves and swells, possibly originating atdistant storm centers and having full access to the shorebecause of the deep water, and seismic sea waves ortsunamis.

In January and February 1983, intense storms movedthrough the eastern north Pacific and struck the southern andcentral California coast with heavy rains, gale force winds, hightides, and heavy surf. These caused widespread shorelinedamage including beach erosion, flooding of shorelineproperty, and damage to structures. In southern California,more than 1,000 homes and businesses were damaged ordestroyed as well as several State highways and fourmunicipal piers. In northern California, over 1,400 homes andbusinesses were damaged or destroyed.

Coastal development in California relies less onelevation for protection than the more common practice ofconstructing residences behind a bulkhead or seawall.Typically, an entire row of structures is protected by onecommon bulkhead. This consists of piles driven beneath theanticipated scour line and sheeting placed and bolted to them.Deadmen or anchor piles are used to resist rotation of the mainpiles (Figure 2-7).


Most storm damage in this area is the result of scour, orerosion, which undermines bulkhead or seawall supports, andexposes to flooding the properties presumably protected bythem. The California coastline has historically had a higherrate of erosion than other U.S. coastlines. This higher erosionrate, coupled with the fact that many California homes are builttoo close to the beach, has led to the well publicizedfailures that accompany winter storms. Elevated houses havenot been immune to undercutting of the supporting piers orpiles by the often deep seated erosion.

In the northern portion of the Pacific Coast region,development pressures are generally less intense, and landuse policies often prevent new coastal development.

2.6 HAWAIIAN COAST

The Hawaiian islands are the tops of a chain ofsubmerged volcanic mountains. As a result of themountainous terrain inland and a climate extremelyfavorable to tourism, many of Hawaii's coastal areas havebeen intensively developed. Hawaii has a varied coastline,from rocky cliffs to wide sandy beaches; the more intensivedevelopment has occurred along beach areas.

The Hawaiian coast is subject to flooding and waveaction not only from severe storms but also from tsunamisseismic sea waves). For example, the 100-year floodelevations around Oahu are those generated by tsunamis.However, considerable beach erosion and some damage toresidential structures occur annually on the north and westcoasts of Oahu from low-pressure storm centers that mayremain offshore for several days. Severe weather isuncommon in this area, and major storms andthunderstorms are infrequent. In an average year, three stormsof tropical storm or hurricane intensity form in or propagate intothe central North Pacific. However, in the

Figure 2-7. Simple bulkhead.


Figure 2-8. Typical bulkhead in Hawaii.

years since World War II, only two have hit Hawaii directly: Dotin 1959 and Iwa in 1982. Hurricane Dot caused propertydamage slightly in excess of $5.7 million, principally on theisland of Kauai. Iwo struck the islands of Niihau, Kauai, andOahu; damage, due mainly to high surf

and winds gusting to 100 to 120 mph, was estimated at $234million. Most of the significant damage was confined to a 2- to3-mile-wide coastal fringe on Kauai. Approximately 13percent of the homes and 55 to 60 percent of the hotel units inthis area were destroyed or damaged.

Two types of flood waves impact on the Hawaiiancoastline: low-pressure-center northwest storm waves andtsunami waves. The low-pressure storm waves causesignificant damage to coastal construction as a result of beacherosion by the continuous onslaught of waves during the storm.A tsunami occurs less frequently, and only a few significantwaves impact the coast; however, the wave runup isconsiderably greater during a tsunami because of the largevolume of water in each wave. This extended runup causessevere erosion of the materials supporting structures wellinland when the wave recedes rapidly.

Figure 2-9. Soil erosion potential.


The tsunami wave is the critical element controllingdesign on all coasts of the Hawaiian Islands. Tsunamisoriginating in the Alaska-Aleutian area have struck northerlyexposed sites. Primary areas affected by tsunamis from thenorth are Hilo on Hawaii and Hanalei Bay on Kauai; damagemay also occur to the northern shore of Oahu, betweenKahana Bay and Kaena Point. The 1957 tsunami didconsiderable damage at Hanalei. However, the tsunamihaving the greatest effect on the Hawaiian Islands was in 1946.Other significant tsunamis in Hawaii since 1946 include:November 1952, March 1957, May 1960, March 1964, andNovember 1975.

Some tsunamis originate south of Hawaii and thus affectsoutherly exposed sites. Although tsunamis originating nearJapan have not been a major problem, one such surge struckthe Kona Coast of Hawaii in 1896. There has not been anysignificant damage in the State of Hawaii from tsunamisoriginating near California or Mexico, but Peruvian andChilean earthquakes have caused considerable

tsunami damage along the southeastern coastline ofHawaii.

In Hawaii, use of design and construction techniques toresist flooding, wave action, and erosion is limited. Aestheticconsiderations and design tradition have had a significantimpact on the resistance to elevating the first floor. A fewelevated residences exist but these are exceptions rather thanthe rule. Beach erosion and the subsequent exposure offoundations are of great concern in several coastline areas. As a result, constructing ads and other beach protectiondevices is much more common than elevating structures.

Bulkheads are commonly used to protect residences onshallow footings (Figure 2-8). Some structures on the northerncoast are constructed directly on the natural sand dune.During low-pressure storms, the toe of the dune is eroded andwaves encroach on the oceanfront of the structures (Figure 2-9).

Site Design Recommendations 3-1

Chapter 3

SITE DESIGN RECOMMENDATIONS

3.1 BUILDING CODE AND ZONING REQUIREMENTS

Building codes and zoning ordinances are normallyenacted by local jurisdictions, either city or county. Theseregulations are intended to control various aspects of acommunity's physical development, such as constructionmaterials and practices, land use, minimum sizes of lots,setbacks from streets and property lines, density ofdevelopment, parking requirements, and height and sizerestrictions. Such controls are not limited to the urban contextand have been applied to all development areas includingrural lands. Coastal area management through the use ofbuilding code and zoning ordinances is as critical to thesensitive needs of this special environment as it is to thecommercial/retail cores of cities. The ordinances are needed toensure public safety, community development, and the integrityof special areas.

Unfortunately, failure to enact or adequately enforcesuch necessary controls has led to uncontrolled landdevelopment in many coastal zones, particularly in regionswhere beach front property has attracted residents for severaldecades. Areas where building codes and zoning laws werenot in effect prior to development exhibit a beachfront clutteredwith construction; a broad range of often substandardconstruction practices; buildings with only a few feet ofseparation, typical of urban and suburban neighborhoods;destruction of the primary dune and its inherent stormprotection; and the creation of both physical and visual barriersto public access to the natural coastline.

Residential construction is the most common land use incoastal communities, with the single-family housepredominating. There is, however, a general trend to multi-unitbuildings due to the high cost of coastal property. Virtually allcoastal areas now fall within the authority of local zoning andbuilding code ordinances. Many local jurisdictions haveimposed strict regulations on new development, particularly inpopular resort and retirement communities, which havebecome perhaps the most active areas of construction in thecoastal high hazard zones.

Local authority often goes beyond the normalregulations to include such items as architectural review,protection of dunes and dune rebuilding, preservation ofindigenous vegetation, and limits on some architecturalfeatures. A review of current building code and zoningrequirements is a first step in preparing for a new constructionproject, or for an addition to or renovation of an existingstructure. This review should determine such requirements as:

• Required construction materials and practicesMinimum lot size

• Setbacks, including the space between structures• Height and size restrictions• Protection of natural features, including the primary

dune• Elevation requirements Access to the beach, both

physical and visual• Utilities protection• Sewerage facilities

The illustrations in this chapter demonstrate the buildingcode, zoning, and other concepts that must be applied to sitedesign in coastal areas. Building construction requirementsfound in local building codes and


other regulations that may be imposed on coastalconstruction, together with site design requirements, make upthe building permit process. Permits are issued only aftercompliance with these requirements has been assured and isproperly documented. Generally, the project is subject toinspection during construction by an authorized representativeof the local authority.

Building code and zoning requirements plus commonsense and experience have influenced site design practicesthroughout the coastal areas of the nation. It should beemphasized that building code and zoning requirements arestated in terms of minimums. While these minimumrequirements have often become the accepted practice in thelocal construction industry, these practices should always beconsidered minimum acceptable requirements. Requirementsfor specific structures, based on engineering considerations,often exceed the code minimums and should be evaluated ona case-by-case basis.

3.2 SITE LAYOUT

Site planning for coastal buildings should followstandard planning criteria applicable to any site work, notmerely orientation based on flood flow. In layout of the site,typical factors such as slopes, natural grades, drainage,vegetation, orientation, zoning, and surrounding buildings mustall be considered, as well as direction of flood flow. Particularcare should be taken to observe the setback from the meanhigh water line and other coastal zone managementrequirements. Access to and evacuation from the buildingshould be a special consideration in flood hazard zones. Hydrodynamic impacts may severely damage roadways andwalkways, leaving the property potentially unreachable byrescue vehicles. If flood waters approach the BFE with allsurrounding land area inundated, rescue may only be possibleby boat or helicopter.

Consideration of existing neighboring structures, suchas residences, bulkheads, trees, and berms, is oftenoverlooked. Adjacent structures may benefit a particular site byoffering a screening effect or diversion. But these samestructures may be damaged by storms and become floatingobjects capable of severe destruction. When it is practical andpossible to do so, the elevated structure should be alignedparallel to the flood flow with the narrower dimension facing thebeach. This simply presents a smaller surface area upon whicha storm can act. The more surface area exposed, the greaterthe likelihood of damage occurring.

It must be emphasized that hazards to coastalconstruction come from the sea. The hazard may be reducedby building farther from the shoreline. Building near the backor street side of a beach front lot reduces as much as possiblethe beach erosion problem.

3.3 LANDSCAPING

A feature not commonly considered to provide physicalprotection from storm hazards is landscape treatment. Some coastal jurisdictions and private developments requireplanting and protection of indigenous vegetation to obtainpermits to build. This is normally limited to plant materials likedune grass, sea oats, and some shrubs like mangrove. Planting and maintaining vegetation, even in areas where nosuch requirements exist, can be a good way to protect theresidence. Vegetation provides a more stable soil condition,can trap windblown sand, and can even act to deflect highwinds and waves that are pounding the area. Larger materialslike shrubbery and trees can also deflect floating debris thatmight otherwise impact the elevated foundation.Landscaping may also provide a pleasant effect ofscreening and reducing the visual impact of the elevatedbuilding.


3.4 DUNE PROTECTION

Dunes provide a natural shoreline defense againststorm wave and water level attack and are often termed anonstructural coastal protection method. Programs for dunerebuilding or enrichment are being conducted in many areasas a preferred alternative to other protection methods, anddune preservation regulations have been enacted. Figure 3-1shows an example of a building site behind a reconstructeddune. Although the protection to a structure located behind itcan be substantial, a dune should not be consideredindestructible and is subject to erosion and scour in majorstorms.

Beach material is usually deposited in offshore barsduring storms and returns onshore after storm passage tobegin beach rebuilding. Sand is pushed shoreward by fairweather winds and is gradually deposited on the beach.Onshore winds then rebuild the dunes with sand from thebeach. This rebuilding process is diminished by the presenceof man-made obstructions.

Figure 3-1. Typical dune reconstruction

Existing dune fields should be maintained throughvegetation stabilization and sand fencing, which promoteadditional dune growth and limit wind losses. The cutting ofroadways or paths through the dune line should be prohibitedand timber crossovers used instead, as shown on Figure 3-2.In areas where no dunes exist and sufficient beach width ispresent, dune construction using successive tiers of sandfencing will promote further formation.

Dwellings should always be placed behind primarydunes (Figure 3-3). Construction atop or in front of dunes isextremely vulnerable to structural damage from storms andshould be prohibited. Figure 3-4 shows the overall constraintson coastal structures due to zoning and setback requirements.

Figure 3-2. Walkway structure and fencing protect the dune.


Figure 3-3. Example of use of building setback requirements tolocate structures behind the primary dune.

Figure 3-4. Zoning restrictions on coastal development.

3.5 BULKHEADS

In a limited number of circumstances, bulkheads can beeffective in reducing storm damage and erosion if designedproperly. However, there are a number of reservationsconcerning their use, including restrictions on their use in Vzones (velocity zones) to meet minimum elevationrequirements under the National Flood Insurance Program(Section 1.2). Bulkheading on an individual lot basis shouldbe avoided. Because of the abrupt vertical transition in profile,bulkheads generally promote toe scour and this can lead tobeach loss and steepening at sediment-starved beaches. Experience has shown that erosion accelerates at adjacentunprotected areas, possibly resulting in the flanking ofindividual bulkheads as shown on Figure 3-5. Structuralsolutions for coastal protection generally require multiple-siteimplementation for maximum effectiveness.

Use of bulkheads in V zones should be limited toremedial protection of existing structures where othermitigating measures, such as elevating an existing building,are considered infeasible. If used, they should be designedonly to withstand storm wash runup--the forward, high-velocityremnant of a broken wave as it continues to run up on shore.Direct wave attack is less effectively handled by bulkheading. Only massive structures of concrete and/or stone canadequately handle severe conditions. Use of bulkheading torepel frequent events usually implies development too close tothe water, and the need for massive and expensive regionalerosion protection.

Where bulkheading is to be used, rock riprap isrecommended as the most effective protection from waves.Because of its sloped surface, voids, and roughness, itdissipates wave energy effectively. Riprap is flexible from astructural standpoint; timber or rock riprap structures can bedesigned for individual sites. Figure 3-6 shows a riprapstructure at Hilton Head, South Carolina.


Figure 3-5. Erosion damage to individual bulkhead.

The following items should be considered in bulkheaddesign:

• Foundation and backfill conditions • Exposure to wave action and scour • Availability and durability of materials • Cost.

Evaluation of these items will determine the structural materialsand geometry used for shore protection. The Shore Protection Manual (USCOE, 1984) contains detailed information on thissubject.

Figure 3-6. Rock riprap used as a bulkhead.

Foundation conditions should be considered in terms ofcompatibility with the structure, backfill loading, and passiveresistance. Flexible structures should be used for sandyconditions, since the bulkhead wall's flexibility will lessen thelateral force of the backfill compared to a rigid structure.Bulkheads that require penetration for stability are not suitablefor rock bottoms. Vertical solid structures are subject to toeerosion in sands and to a lesser extent in soft clays, and shouldbe protected from toe sliding effects due to bottom scourinduced by the wall itself. This scour can also cause settlementand tipping with gravity structures. Scour problems can bereduced by altering the geometry. A recurved wall shape(Galveston type) as shown on Figure 3-7 directs wave runupaway from the toe of the wall and may lessen scour.


Figure 3-7. Concrete seawall with recurved face.

Wave action may determine the selection of structuraltype and design geometry. Light structures such as timberpiles and lagging or small stone revetment are compatible withsmall wave action. However, direct wave attack dictates moremassive structures, such as curved concrete seawallsdesigned to dissipate wave energy by upward verticaldeflection. Calculation of wave forces, as summarized in the Shore Protection Manual , determines the structural materialnecessary to withstand the anticipated energy.

An important aspect of designing a shore protectionsystem is the selection of materials of adequate strength anddurability for the specific physical conditions of a site.Consideration of initial cost plus maintenance will

determine the most economical design. Durable rock, readilyavailable and inexpensive in one area, may be too distant fromanother.

Professional consultation is recommended to engineer afunctional structure properly. The Shore Protection Manualsummarizes the various analyses of coastal processes thatshould be considered. Structural solutions to shore protectionshould attempt to work with the existing natural forces; themore one resists coastal dynamics, the greater is theprobability of encountering serious problems.

3.6 USE OF EARTHFILL

Constructing residential structures on engineered fill isone means of elevating the living areas of the house a abovea required elevation in riverine flood plains. However, incoastal zones the scouring action of waves can erode the filland expose the foundation to the point of failure. Even ifproper slopes are provided for the fill and protective measuressuch as riprap, vegetation, or landscaping with grass areapplied to the seaward slopes, there will remain concernregarding its adequacy. For these reasons, the use of earthfillto elevate structures in coastal high hazard areas (V zones) isprohibited by NFIP.

The use of earthfill for landscaping purposes may beappropriate for some V zone locations. However, care must beexercised to allow for the unobstructed flow of velocity watersand wave action. Improperly located or large size earthfillsmay ramp damaging waves into the elevated portion of astructure.

In coastal A zones, the use of earthfill for elevationshould be restricted to those areas subject to minimal velocitywater and wave action, due to the potential for scour anderosion.

Structure Design Recommendations 4-1

Chapter 4

STRUCTURE DESIGNRECOMMENDATIONS

This section discusses the design of residentialstructures to resist the effects of coastal winds and flood waters. It includes an examination of various forces present in thecoastal environment, their range of magnitudes, and somerecommendations and sources of additional information. Dataare also presented on various construction materials forresidential structures in coastal high hazard areas, withdiscussions of corrosion and the need for wood treatment. The major portion of this chapter presents recommendeddesign details from the foundation to the roof. Acceptablealternatives are presented wherever possible. One shouldconsider these recommendations as minimum requirements. Local experience or site specific information should be used toimprove the quality of design and construction.

Several cautionary statements are appropriate,however. The information presented in this manual is basedupon values of forces and properties of materials taken from standard engineering references and conventional buildingcodes. A limited range of sizes and configurations for single-family residences has been assumed for purposes ofestablishing design criteria and tables (Appendices A and B).

Since this design manual attempts to informhomeowners and builders in coastal regions throughout theUnited States, site-specific situations have not beenaddressed, only the general cases covered by building codes.An example is the case of wind speeds, for which a realisticrange is considered after evaluating various building codevalues. Generally, conservative approaches

and values have been used to provide conformance with mostapplicable building codes throughout the United States.

The flood forces considered in this work include forcesgenerated by wave action. Water and wave forces arecalculated to be consistent with the wave crest elevations thatwould be present during the base (100 year) flood, the eventthat has a 1 percent chance of being equaled or exceeded inany given year.

4.1 ENVIRONMENTAL FORCES

Conditions found in the coastal environmentsdescribed in Chapter 2 impose stresses on constructionmaterials that are not imposed in the inland environment. Ifspecial precautions are not taken, deterioration of wood andmetal building components is accelerated. Masonry andconcrete are affected to a lesser degree except where noted.

4.1.1 WIND

A major concern in the design of residential structures incoastal regions is the magnitude and effect of high windsduring storms. In this report, the basic wind design data andprocedures follow the recommendations included in NationalStandards Institute Minimum Design Loads for Buildings and Other Structures , ANSI A58.1-1982. A number of otherbuilding codes are also referred to, including the StandardBuilding Code, the BOCA Basic National Building Code, andUniform Building Code.

The wind velocities, pressures, and design coefficientsused in this report are those presented in ANSI A58.1-1982.The recommended basic wind speed at a site should be the 50year mean recurrence interval (Figure 4-1) times animportance factor of 1.11 for correcting to a 100 year


Figure 4-1. Basic wind speed in miles per hour, 50-year recurrence interval.


recurrence interval in coastal areas. The design tables inAppendix A were developed for a range of wind speeds from80 to 140 mph, which satisfies nearly all coastal arearequirements. Because of the large forces exerted by windsgreater than 140 mph, various connections require spacialattention. This is beyond the scope of this manual and a designprofessional should be consulted.

The elevation above grade of the roof of the house is aparticularly important parameter in determining wind upliftforces. As the roof height increases, there is an increased upliftforce on the rafter connections and related components downthrough the foundations. The design tables include such loadincreases, which can be significant on houses with a secondstory or loft area and a first floor elevated 8 to 10 feet abovegrade in order to be above the BFE. In some coastal areas, theheight of water plus waves may approach 20 feet; obviously,the roof of a one-story house in this situation will be quite high.

Elevating above the base flood increases theprobability that the structure will overturn unless adequatelydesigned and constructed. Therefore, the design tablesrequire information regarding the heights above ground levelof various parts of the structure, so that the appropriate forcescan be considered in the design.

The following discussion and illustrations on how windforces act on a typical one-story house will be helpful to homebuilders and other users of this design manual. Sketches areprovided so that these effects may be more easily understood.

Flowing wind exerts pressure on a structure and itscomponent parts. The horizontal pressure on the front wall anda horizontal suction on the rear wall cause an overturningeffect, as shown in Figure 4-2. Also, these

wind pressures can slide the structure off its foundation, asshown in Figure 4-3.

Since the wind speeds up as it flows over the roof, ittends to suck the roof upward and off (Figure 4-4). Internalpressures also change, especially if wind enters the buildingthrough failed windows or doors. With an opening in thewindward wall, internal pressure increases; if an opening

Figure 4-2. Wind overturning forces.


Figure 4-3. Wind sliding and bending forces.

occurs in a side or leeward wall, internal pressure decreases. Figure 4-5 shows how these forces could combine with upliftforces to blow off the roof. Figure 4-6 shows how thecombination of built-up wind pressure inside the structure andsuction pressure on the side walls and rear wall tends toexplode the walls. A house on Dauphin

Figure 4-4. Wind pressure on roof and eaves.

Island, Alabama, that received major damage from windsduring Hurricane Elena is shown on Figure 4-7. The home hada large porch on the windward side that was lifted totally off thestructure, probably in part due to internal pressures. The housealso has several large sliding windows that were damaged,and part of the roof was lost.


A common myth about hurricane resistance is thatwindows should be left open to equalize internal and externalpressures. In reality, if a wind enters a windward opening, theincreased internal pressure on roof and walls is much morelikely to cause damage than if the wind is acting onlyexternally. The houses that best resisted Hurricane Alicia'shighest wind forces invariably had storm-shuttered windowsand doors that remained intact.

Figure 4-5. Wind pressure on roof when wall opening occurs.

The important factors in minimizing wind damage to abuilding generally are use of shutters to keep the buildingenvelope intact, and adequate anchorage to transmit windforces from the roof down through the foundations. At aminimum, buildings should have windows that are rated for thedesign wind speed at the site. For further protection againstwindow breakage from debris impact, storm shutters arestrongly recommended.

Figure 4-6. Wind pressure on walls when wall opening occurs.


Figure 4-7. Damage from internal pressure.

Particularly high wind pressures occur at corners of ahouse, at and under roof eaves, and at the peak of the roof(Figure 4-B). This is caused by the patterns of wind flow atthese critical points. This design manual provides guidance inthe connection details necessary to resist wind forces.

High wind forces tend to stress the connections betweenstructural members, such as those connecting posts and pilesto beams and those connecting beams to joists and verticalsupports. Such stresses cause a progressive weakening ofthese connections to the point where failure is possible. Figure4-9 shows a house that was separated from its foundationplatform during Hurricane Alicia.

It cannot be overemphasized that attention toconnection details for rafters, joists, and stud walls (at cornersand at bottom and top plates) can reduce wind damage. Whenthe structure is tied together as an integral unit it can betterresist dynamic forces such as those due to wind, floodwater,waves, and even earthquake. For this reason, there should bea continuous series of positive connections from the roof raftersdown through the walls to the first floor joists, supportingbeams and piles, or other foundation system. Joist anchors,well-nailed plywood sheathing, metal straps, bolts through floorbeams and piles, and similar connections all contribute to awind-and flood-resistant structure. These elements areaddressed in more detail later in the chapter.

Figure 4-8. Wind pressure on corner overhangs.


Figure 4-9. Removal of house from foundation piles by wind forces.

4.1.2 Salt Air, Moisture, and Wind-Driven Rain

Coastal areas have a highly corrosive atmosphericenvironment resulting from inland transport of salt spray by thewind, combined with generally higher moisture levels in the air.These corrosive conditions can extend several miles inland,but are most severe close to the sea. The undersides ofelevated structures are particularly vulnerable to salt spray,because the exposed surfaces are not washed by rain and staydamp longer due to their sheltered location.

Moisture with a high salt content is extremely corrosiveto ferrous metals and mill-finish or nonanodized aluminum. Italso tends to increase swelling and shrinking

cycles, rot, and insect activity in wood. Galvanizing is the mostcommon protective coating for steel fixtures. Bolts, nails, andother hardware items are usually hot-dipped galvanizedfollowing fabrication. The steel plate connectors--often referredto in coastal areas as "hurricane clips"--described in thismanual are commonly manufactured from pregalvanizedsheet. These connectors perform well in protected locations,such as the interior of a building, but have only a limitedlifespan in exposed areas. Heavier weight connectors that arehot-dipped galvanized after fabrication are preferred inexposed areas. All metal connectors are subject tocorrosion over the life of a structure. Routine inspectionsand maintenance (see Section 4.3.8) are necessary toensure the continuing serviceability of connections.

Wind-driven rain has been a continuing problem incoastal areas under storm conditions. Commonly availablewindows, doors, and roof ventilators were designed for inlandlocations and have been found to leak from the wind-drivenrain of coastal storms. This problem has been recognized;storm-rated products are now available and should bespecified for all new and replacement applications. Carefulinspection of a coastal building should be conducted to identifypotential water pathways through the building's exteriorenvelope, and sealants and caulking applied wherenecessary.

The combination of high winds and moist salt-laden aircan also have a damaging effect on masonry construction byweakening mortar bond and permitting moisture penetration.Although concrete is less affected by the coastal environmentthan other construction materials, special precautions such asincreasing the thickness of concrete cover over thereinforcement should be taken to prevent moisture fromreaching the reinforcing steel through the hairline crackspresent in all concrete. Rusting of the steel may cause stainingand could contribute to


spalling of the concrete and exposure of the reinforcement.Additional precautions for the coastal environment areespecially important for larger buildings (Chapter 5) due to theextensive use of reinforced concrete in these structures.

4.1.3 Water, Waves, and Debris

Structures located in coastal environments aresubject to a number of loads and natural forces associated withsevere storms, including the 100 year flood. If the site is in theV zone, the wave crest elevation of the 100 year flood will be acritical design parameter that must be determined.

The water forces on the piles that elevate structuresabove the ground are primarily the momentum of waterimpinging on the pile and the drag force in the direction of thevelocity of the water. Similar forces act on breakaway or latticewalls, stairways, and utilities below elevated structures. Onemust therefore consider the stillwater storm tide elevation aswell as the associated wave action (wave crest elevation). In Vzones both flowing water and save action are to be considered,while in A zones only a save height less than 3 feet isconsidered in addition to flowing water.

The home builder and/or designer should obtain theBase Flood Elevation for his site by referring to the FIRM for thecommunity. Use of the water depth plus wave height as shownon the FIRM is an important factor since the design tables relyon water depth plus wave height to determine lateral forcesand the proper flood-resistant design.

The velocity of coastal flood waters can result inmovement of debris, which includes portions of houses, utilitypoles, fences, etc., such as the debris shown adjacent to ahouse in Alabama following Hurricane Elena (Figure 4-10).These objects may collide with residential structures; theresulting impact loads are a function of velocity of the object(assumed equal to the velocity of the water) and the timerequired to stop (decelerate) the object upon impact. Thedeceleration time is in turn related to the distance over whichdeceleration occurs, which is considered equal to piledeflection upon impact. This design manual has provided forthe collision of a 300-pound object moving at surface watervelocity and decelerating over a maximum distance of 0.5 foot.The collision is assumed to occur against one pile at thehighest elevation of the flood waters.

Figure 4-10. Waterborne debris deposited against foundation piling.


Note also that larger debris, such as that shown in Figure 4-10,can wedge against foundation piling and bracing, increasingwater forces on the foundation system.

4.1.4 Effects of Forces on Higher and Larger Structures

This report includes design of residential structureselevated up to 22 feet above grade to provide for the bottom ofthe lowest structural beam to be above the BFE. About onestory of elevation is required in many areas. If the clear heightneeded is less than about 8 feet, it is likely that the builder maystill elevate the structure to about one story to provide parkingand storage under the house.

For structures required to be elevated more than about12 feet above grade, forces on the supporting piles increaserapidly with increasing height. Uplift forces will be higherbecause wind suction increases as roof height increases.Also, the overturning forces against the piles will be greaterfrom both wind and water. Therefore, the piles must be longer,stronger, and better braced, and will be more expensive interms of material and installation. For these greater heightstrussed bracing may be required. Design data for this bracingand determination of the need for it are included later in thismanual. Due to the complexities of the design, a qualifiedarchitect or engineer could be helpful in designing thesehigher structures.

Similar considerations are necessary for buildingstructures larger than a two-story house. For example, theforces on a three- or four-story motel are much larger thanthose considered in this report. This is because the upliftforces on a higher roof are larger and because the frontal areaof walls is greater and receives a larger wind force tending tooverturn the structure or move it laterally. Consultation with aqualified professional architect or engineer is recommended.The procedures in

Chapter 5 of this design manual demonstrate the approach tobe used. However, the details of design, including magnitudeof forces, selection of pile type and method of installation, andsize of beams and connections all require specific attentionbeyond the scope of the design guidance and tables includedin this manual. This is also true when wind speeds exceed 140mph, in which case this manual cannot be used alone andprofessional help is needed.

4.2 CONSTRUCTION MATERIALS

Wood is the most available and most commonly usedmaterial for one- or two-family residential structures in thecoastal environment. With proper selection and design, woodcan handle most loadings and spans. Steel and concretematerials are used on a limited basis. Since most steelscorrode severely when placed near the ocean, the use of steelrequires caution and a thorough understanding of itscharacteristics. Certain alloy steels are available, but their useis advised only with the assistance of a qualified professional. Likewise, concrete can be used as a construction material,but the cost of forming and the special nature of connectionsmust be considered. Precast concrete may be suitable forbeams and other structural members. Residences elevatedmore than 15 feet above ground may be built moreeconomically with precast concrete piles and beams becausewood piles need to be longer (embedded deeper) and requirea substantial bracing system.

4.2.1 Wood

4.2.1.1 Piling. The properties desirable in piles includesufficient strength and straightness to carry the weight of thestructure, withstand pile-driving forces at installation, and resistthe bending stresses of wind and waves. Southern


yellow pine, Douglas-fir, and oak are among the principalspecies used for piling, but western red cedar and numerousother species also are used.

Decay resistance and ease of penetration bypreservatives are particularly important. Pilings that supportthe foundations of buildings should be pressure treated withwood preservative to a retention suitable for ground contact.

4.2.1.2 Main Supporting Members (Beams). The mainsupporting beams attached to piling, posts, masonry piers, orwalls in turn carry the floor joists and subflooring. Thesemembers are either solid timbers, such as 4-by-10's, or arebuilt up using standard framing lumber such as two, three, orfour 2-by-10's spiked or bolted together. Where beams arebuilt up using a good grade of lumber for the laminatedmembers, the strength of the built-up beam may equal that of asolid member. All members of the built-up beam should becontinuous between supports, as splices materially reducestrength. Built-up members should include only one splice atany one location. The ends and tops of built-up membersshould not be directly exposed to the weather. Lumber thathas been pressure treated for exposure but not for groundcontact is recommended for beams and decks.

4.2.1.3 Other Wood Construction Members. Floor joists,studs, bridging, blocking, soles, sills, and plates are notrequired to be preservative treated, although such treatmentmay be helpful in regions of highest decay and insectinfestation.

4.2.1.4 Wood Preservatives. Any wood members used forpilings and floor beams, whether exposed or enclosed, solid orbuilt-up, must be treated with chemicals or preservatives toresist insect infestation, dry rot, decay fungi, and the effects ofexposure to salt air and water. It

is important to remember that this environment has as great atendency to harm concealed beams as those left exposed.Enclosed beams may in fact be in more danger, since they lackthe ventilation that would allow collected moisture to evaporateand are not exposed to rain water to wash away precipitatedsalt compounds.

Good wood preservatives, thoroughly applied withstandard retentions and with the wood satisfactorily penetrated,substantially increase the life of wood structures. On this basis,the annual cost of treated wood in service is substantiallybelow that of similar wood without treatment. Woodpreservatives fall into two general classes: oils, such ascreosote and petroleum solutions of pentachlorophenol; andwaterborne salts, such as chromated copper arsenate (CCA).

The degree of protection obtained depends on the kindof preservative used and the thoroughness of application.Some preservatives are more effective than others and someare more adaptable to certain use requirements. Furthermore,the wood is well protected only when the preservativesubstantially penetrates it. Some methods of treatment assurebetter penetration of various species of wood, particularly of theheartwood, which generally resists preservative treatmentmore than sapwood.

Generally, the type of preservative used and the needfor substantial penetration of the wood is of crucial importanceonly in applications where the wood is directly exposed tosaltwater, such as wood used for piers or bulkheads. Housefoundations are somewhat more protected and should beinundated only rarely, so the marine borer problem is lessrelevant. Pressure treatment suitable for ground contact isappropriate for pilings supporting residential structures, andpressure treatment of wood suitable for uses lacking groundcontact is appropriate for all elevated members.


4.2.2 Masonry Materials and Concrete

In general, masonry materials and concrete perform wellin the coastal environment. Adequate reinforcing must beprovided to withstand stresses and, as mentioned earlier,coverage of reinforcement must be sufficient to reduce thedanger of salt water reaching the steel and consequent rustingand staining. Special care should be taken in the quality ofconcrete and masonry units and of mortar used to reduce voidsin surfaces and between joints in masonry work.

4.2.3 Metals

4.2.3.1 Aluminum. Construction elements or assemblies suchas doors, windows, gutters, downspouts, and flashings madefrom mill-finish (uncoated) aluminum sheet or extrusionsdeteriorate rapidly from corrosion in the coastal environment.The heavier anodizing finish (0.7 mil) is recommended.Nevertheless, moving parts, hardware, hinges, sliding doorsand windows, and jalousie operators require additionalmaintenance. A heavy vinyl finish on these components offersprotection approximately equal to the anodizing finish.

4.2.3.2 Steel. Exposed structural steel shapes, beams, pipes,channels, and angles undergo very rapid corrosion and theiruse should be avoided in the coastal environment. Smallconnecting devices such as bolts, angles, bars, and strapsshould be hot-dipped galvanized after fabrication and coatedwith a protective paint after installation. Heavy, hot-dippedgalvanizing can last 20 to 30 years in the coastal environment.Standard galvanized sheet metal joist hangers and otherconnecting devices deteriorate more rapidly despite theirgalvanized coating and require additional protective coatingsand more frequent replacement. Small anchoring devices,nails, spikes, bolts, and lag screws should, whenever possible,be hot-dipped

galvanized. Where sheet metal clips and hangers are used,the special nails should also be galvanized.

Regular inspection, maintenance, and replacement ofcorroded metal parts are necessary when steel is used in thecoastal environment. When selecting new or replacementhardware, consideration should be given to use of 304 or 316stainless steel, Monel, or other more corrosion-resistantmaterials. As noted by Rogers (1985b), the higher initial cost ofthese materials may well be offset by lower future maintenancecosts.

4.2.3.3 Dissimilar Metals. When two different metals are incontact in the corrosive coastal air, rapid corrosion of one of themetals can occur. Cathodic protection systems use thisprinciple to advantage by attaching bars of zinc or othersacrificial material to the steel structure to be protected.Usually, however, the corrosion between dissimilar metalsoccurs when they are inadvertently placed in contact by thebuilder or owner. For example, the use of brass screws (whichare suitable for fastening steel) to attach an aluminum framewill result in rapid corrosion of the aluminum. Wheneverpossible, the use of dissimilar metals together should beavoided unless the safety of the combination ion has beenresearched. Aluminum screws would have been preferred inthe example. Stainless steel reacts less with aluminum thanbrass and would have been an acceptable alternative. Monelshould not be used with either aluminum or galvanized steel.

4.3 DESIGN DETAILS

4.3.1 Foundations

Several types of foundations are suitable for supportingelevated residential structures in coastal high hazard areas.Tapered cylindrical or square wood piles are the most commonfoundation. Another popular but


structurally weak method of elevation uses wood posts restingon a spread footing. A variation of this is reinforced masonrypiers resting on spread footings or concrete grade beamsunder a concrete slab. In some locations shear walls ofreinforced masonry or concrete at right angles to the beach(and thus parallel to the likely flow of flood waters) have beenused. In some instances concrete piles or steel piles havebeen used, particularly for structures larger than a two-storyresidence. Various foundation types are discussed below inmore detail, together with the role of soil conditions infoundation selection and design.

4.3.1.1 Soil Conditions. An important parameter forfoundation design that must be established early in the layoutand design of a structure is the depth and quality of the soil orrock at the building site. Sand is the dominant soil deposit inmost coastal areas. However, in some areas clay underlies athin (several foot) layer of sand. The mechanism anddistribution of strength for supporting piles in clay differ fromthose in sand. Generally, clay soils provide greater capacitywith less penetration than sandy soils. Some builders use awater jet to insert piles into sand; this technique alone is notsufficient to allow piles to penetrate clay, which normallyrequires an auger or pile driver. The design tables in AppendixA include pile capacity for each of four types of soil: mediumdense sand, loose sand, medium stiff clay, and soft clay.

Clay also performs differently from sand under waveaction and is affected little by scour. The depth of scour ofsandy soils under wave action is difficult to predict accurately,but can be several feet from severe storms. It is important thatpiles supporting residences on sandy shorelines penetrate aminimum distance into the ground to provide resistance to windand water loads even after extensive scour from a storm hasoccurred.

Pile penetration depths in sand should allow for scour ofboth loose and dense sand from around the pile foundation aswell as temporary liquefaction of some of the sand near thesurface during storm conditions. Figure 4-11 shows a housethat settled nearly intact when the piles lost their supportthrough scour or liquefaction.

There are other rules of thumb that can assist in theevaluation of soil conditions at a building site. Loose sand ispenetrated with a 1/2-inch reinforcing rod pushed by hand.Medium dense sand is easily penetrated with a 1/2-inchreinforcing rod driven with a 5-pound hammer. Althoughdenser sands may exist at a site, under storm wave action it isexpected that loosening of the sand and scour will occur; thedesign tables in the appendices reflect this. If clay is

Figure 4-11. Nearly intact settling of a house when piles lost capacity.


present at a site, a sample should be obtained. It is classifiedas soft clay if it is easily molded by the fingers and medium stiffclay if molding by the fingers requires strong pressure.

If soil boring data are available, classification into thesoil categories listed above is possible from the standardpenetration test. This involves driving a 2-inch-diameter, thick-walled tube sampler by a 140-pound weight dropping 30inches onto the drill rod. The number of blows per foot to drivethe sampler is counted and is a rough indicator of soilconsistency. In sands, 10 blows per foot (bpf) or fewer indicatea loose sand. Higher blow counts indicate medium densesand for purposes of this design manual. Soft clays are thosewith 4 or fewer bpf, so higher blow counts would indicatemedium stiff clays. Boring data from adjacent or nearby sitesmay be useful in establishing the general soil conditionsunderlying a site. For example, soils on barrier islands areoften more uniform than at inland locations. Adjacent sites thesame distance from shore would likely have similar subsurfaceconditions. When interpreted with care, data from nearby sitescan be quite useful.

Rock is encountered at or near the ground surface alongsome portions of coastline, and specific local foundationpractices have evolved to provide the required lateral and upliftresistance in V zones. In the Florida Keys, for example, it iscommon to install foundation systems socketed into therelatively soft limestone by augering or drilling several feet intothe rock, then filling the socket with concrete. Reinforcing steelin the socket extends into the piers above. Where harder rockis encountered, such as in New England, steel dowels aregrouted into holes drilled in the rock and used to anchorconventional piers.

Figure 4-12. Elevating with wood piles.

4.3.1.2 Piles

Pile Selection. Wood piles are probably the most widelyused foundation for elevated residential structures (Figure 4-12). In some locations, square timbers are preferred overround piles because of cost, availability, and ease of framingand connecting the structural beams to the piles. The mostpopular sizes are 10-inch and 8-inch square, rough-sawnmembers. The latter size is the minimum size generallyapproved for use in coastal high hazard areas. In regionswhere the design wind speed is greater than 100 miles perhour, the row of residences fronting on the beach should have10-by-10 piles if square timbers are used. These


provide greater resistance against uplift and lateral forces than8-by-8's. Current practice in some locales already requires thelarger piles.

Tapered timber piles with a circular cross section arefrequently used in coastal areas. Generally, these areavailable in longer lengths than square timbers, and for lengthsgreater than about 25 feet it may be necessary to use taperedpiles. When longer piles are required, many builders prefer theround piles because they can provide greater cross sectionarea, peripheral area, and stiffness than square sections,particularly the B-by-B timbers. A minimum tip diameter ofabout 8 inches is recommended for tapered piles.

Figure 4-13. Effect of scour--wind and water forces on piles.

Availability may be the controlling factor in selecting amember; locally available products, stocked by local materialdealers, are usually the most cost-effective materials. If bothsquare and round shapes are equally available, the squareprovides some advantages; it is easier to frame beams into, iseasier to plumb while driving, and is usually straighter andmore uniform in appearance. The additional cost of thedressed square pilings may be overshadowed by theirincreased workability and availability at most lumber dealers.Round piles are, however, available in larger sections andlonger lengths.

Concrete piles are commonly used in coastal areaswhen higher capacity or longer length is required. Theirapplication is mainly on mid- to high-rise structures, althoughcircumstances may occasionally warrant their use on smallerresidential structures. Concrete piles are precast offsite, witheither conventional or prestressed reinforcement, and areavailable in a variety of sizes and lengths.

Pile Embedment. Piles must resist downward loadsdue to the weight of the structure, its contents, and itsoccupants. The piles must also resist upward loads due towind uplift. Wind and water impose lateral (horizontal) forces,which piles resist by bearing against the soil. Therefore, pilesshould be well seated in fairly dense soil. Figure 4-13 showspiles with inadequate embedment; the piles rotated but did notbreak at ground level. Inadequate embedment was likely thecause of the leaning shown in Figure 4-14. The figures andtables provided in this design manual recommend depths ofpile penetration into various types of soil as dictated by thewind and flood water conditions anticipated, the size of thebuilding being constructed, and the number, spacing, andarrangement of piles used.


Figure 4-14. Effect of storm forces on foundation system withinadequate pile embedment.

The depth of potential scour during the design storm willvary for each coastal location. It is critical that piles beembedded well below the scour depth to provide adequatefoundation support during a storm. Historical data on localscour may be helpful in determining the embedment depth, asdescribed in Chapter 3. Standard construction practice forpile embedment depth is inadequate in many coastal areas.Rules of thumb, such as "piles should be embedded as muchbelow ground as above ground" generally underestimate therequired pile embedment and have not taken scour intoconsideration.

Determining an appropriate embedment depth requiresconsideration of several factors (see Figure 4-15), such as:

• Pile depth necessary to resist vertical, uplift, andhorizontal loads

• Anticipated scour depth or elevation at the site• Existing ground elevation• Base flood elevation

Figure 4-15. Pile embedment.


To provide minimum embedment criteria for coastalconstruction, it is recommended that piles in the V zonepenetrate sand to at least a tip elevation of -5 msl (5 feet belowmean sea level) if the Base Flood Elevation is +10 msl or less.If the house must be elevated above +10 msl (expected heightof water plus waves) then the pile tips should penetrate at leastto -10 msl. Many communities have adopted the rule of thumbthat piles should be embedded to -10 msl, which may beinadequate, depending on location. This standard should beconsidered as one criterion only, and the tables provided inthis manual should be consulted to determine if deeperembedment is necessary.

The soil surrounding the embedded piles provides theprincipal resistance at the ground line to lateraldisplacement resulting from horizontal wind and water loads.Additional resistance can be achieved by using horizontalbracing (grade beams) as discussed in Section 4.3.3.2.

Pile Installation. A major consideration in theeffectiveness of pile foundations is the method for insertingthe pile into the ground. This can determine the amount ofresistance to load the piles will have. The best procedure forinsertion is the use of a pile driver, which uses leads to hold thepile in position while a single- or double-acting hammer(delivering between 5,000 and 15,000 foot-pounds of energy)drives the pile into the ground.

The pile driver method, while cost-effective for adevelopment with a number of houses being constructed atone time, can be expensive for a single residence. A drophammer (Figure 4-16 is a modest alternative to the pile driver.The drop hammer consists of a heavy weight (several hundredpounds) that is raised by a cable attached to a power-drivenwinch. The weight is then dropped 5 to

Figure 4-16. Pile installation using a drop hammer.

15 feet onto the end of the pile. The advantage of driving thepile compared to other methods that will be mentioned is thatthe driving operation forces soil outward from around the pile,densifying the soil and causing increased friction along thesides of the pile, which provides greater pile load resistance.


Figure 4-17. Square piles set in preaugered holes.

A disadvantage of pile driving, particularly with lightequipment, is that final pile locations and orientation can vary,depending on the driving conditions. This can complicatesubsequent construction of floor beams and bracing, though itis not usually a significant problem in coastal areas underlainby relatively uniform sand and clay

layers. Large buried material such as logs, gravel bars, andabandoned foundations can result in pile installationdifficulties, whatever method is used. It is prudent to inquireabout subsurface conditions at the site of a proposed structureprior to committing to the type of pile or the installation method.

A much less desirable but frequently used method ofinserting piles into sandy soil is "jetting." Jetting involvesforcing a high pressure stream of water through a pipeadvanced alongside the pile. The water blows a hole in thesand into which the pile is continuously pushed or droppeduntil the required depth is reached. Many contractors then tampsand into the cavity around the pile and pound on the and ofthe pile with the heaviest sledge hammer or other weightavailable. Unfortunately, jetting loosens not only the soilaround the pile but also the soil below the tip. Therefore, only alow load capacity is attained, and the piles must be inserteddeeper into the ground than if they were driven. If piles arejetted into position at a site considered to have medium densesand present, pile lengths and embedment depth should becalculated assuming that loose sand is present.

If the soil is sufficiently clayey or silty, a hole may beexcavated by an auger or other means. The hole will stayopen long enough to drop in a pile (Figure 4-17). Even somesands have enough clay or silt to permit the digging or drillingof a hole. Sand or pea gravel may then be poured and tampedinto the cavity around the pile. Final driving is performed with asledge hammer or large weight. Again, this does not provideas good load resistance as driving the pile into the ground.

If precast concrete piles or steel piles are used forfoundation support and elevation, only a regular pile driver withleads and single- or double-acting hammer should be used.The hammer should deliver at least 15,000 foot-pounds ofenergy. Steel piles are less desirable because of


Figure 4-18. Sketch of foundation for house near Malibu Beach, California.

corrosion problems. Concrete piles can be practical whencombined with either precast concrete floor beams or withwood floor beams as shown in Figure 4-18. Such a structuralsystem can be efficient, economical, and weather and stormresistant. Proper connections between piles and floor beamsand between floor joists and floor beams are necessary.

4.3.1.3 Posts. Wood posts are not recommended in coastalhigh hazard areas (V zones) or coastal A zones subject towave forces and/or scour and erosion. This is because woodposts have low resistance to lateral forces, and there ispotential for undermining of the foundation or footingsupporting the post.

Wood posts can be used in locations where theanticipated wind and flood water forces are low enough to beresisted by a simpler substructure system. The bottoms of theposts should be bolted to metal straps or angles that are firmlyattached to the foundation. The foundation may consist ofreinforced concrete spread footings, usually with a reinforcedconcrete slab, or it may be a concrete pile or pier cast in placein the ground with adequate penetration to resist the appliedloads. If the posts have good knee bracing or are otherwiselaterally supported, they can resist the lateral forces of slow-moving flood waters (not waves) as well as winds ofmoderately high velocity.

4.3.1.4 Piers. In some areas it is common to use reinforcedmasonry piers to elevate residential structures. If used in Vzones or coastal A zones, piers must be properly reinforcedand adequately anchored to a foundation that extends tosufficient depth to resist scour and lateral forces. Generally, alikely place for pier construction is back from the beach, or inother areas where flood waters move in and out with lowvelocity, such as small bays.


Figure 4-19. Sketch of concrete masonry unit pier.

One region where piers are commonly used in V zonesis the Florida Keys. Foundations there are socketed severalfeet into holes augered in the limestone, and then eitherconcrete or reinforced masonry piers are used to elevate thefirst floor.

At locations protected from scour and erosion, piers maybe founded on conventional spread footings, grade beams, orslabs on grade. The pier acts as a beam cantilevered from thebase slab, and grade beams or footings resist horizontalbending caused by wind and water forces (Figure 4-19).Therefore, a substantial spread footing or grade beam withreinforcing steel dowels extending into the pier to resist tensilestresses is required.

Figure 4-20. Concrete masonry unit piers supporting concreteframing platform.

Footings should be at least 3 feet square and embedded atleast 2 feet below grade. The grade beams should be at least12 inches deep below the base slab all around the perimeter ofthe house, with similar beams under the slab running at rightangles to the beach and parallel to the direction of potentialwater flow. The grade beams should be at least 18 inches wideand have at least two 5/8-inch-diameter bars top and bottom. Ifclay occurs within 2 feet of the footing or grade beam, aprofessional should design the foundations to provideadequate vertical and lateral resistance. The requiredreinforcement for various pier sizes under ranges of wind andassociated water loads is provided in Appendix A. The slab ongrade should be concrete with suitable steel meshreinforcement.


Figure 4-21. Floor beams bolted to wood metal straps tying floorjoists to floor beams.

Wherever piers are used in coastal areas, there shouldbe a positive connection at the top of the pier from the concretein the hollow-core masonry units to the floor beams. Thisconnection may be reinforcing steel dowels cast into aconcrete floor beam (Figure 4-20) or it may be a well-anchoredmetal strap bolted through the floor beam (Figure 4-19).

4.3.2 Framing

Once the required elevation is achieved by the methodsdescribed in the preceding section, the next step is to frame thefloor, wall, and roof systems. The framing provides thestructural support or skeleton for the remainder of the buildingand is made up of the floor

beams, floor joists, wall studs and plates, roof (ceiling) joist,and wall and floor sheathing.

4.3.2.1 Framing Methods. The most common framing methodpresently in use is platform construction. This method issuitable for all the foundation systems previously discussedand is in widespread use throughout the country for residentialconstruction. Platform construction in the beach environmentprimarily means bringing the elevating

Figure 4-22. Pole construction details.


foundation, either piles or piers, up to the first-floor level (Figure4-21). Between these supports span the floor beams, to whichthe floor joist framing is connected. A diaphragm or wood floorsystem ties the floor joists together to form the platform. Aplatform is constructed for each floor surface. Once the platformis built, walls, subsequent floors, and the roof are framed abovethe platform and properly connected to it.

The other framing method used in residentialconstruction is pole construction. This system differs mainly inthat the foundation members (usually piles) are extendedabove the level of the first floor to the roof framing (Figure 4-22). Floor and roof beams then are framed directly to thesemembers, securely anchoring the entire structure. Thistechnique can be very effective in resisting severe stormconditions, as it ties the structure together throughout its heightand increases the ability to resist laterally applied forces.These systems are usually more successful using square woodpiles for the foundation m. Compared to cylindrical piles,square shapes make framing easier and better accommodateinterior partitioning.

Pole framing can provide an unusual structure andarchitecturally stimulating spaces both inside and outside.Pole frame houses have the disadvantage that errors orDifficulties in pile installation can result in pile spacings andorientations that make subsequent framing and finishing ofthe house difficult. However, careful measurement andother precautions during pile installation can generally preventsuch problems. The best pole framing designs are those thathave ample tolerance for pile installation error.

4.3.2.2 Beams. The primary floor beams spanning betweensupports should preferably span in the direction parallel to heflow of potential flood water and wave action. This orientation(normally at right angles to the beachfront

Figure 4-23. Typical pile, floor beam, floor joist arrangement,showing bolted beam/pile connection and hurricane clipconnections to floor joists.

allows the lowest transverse member perpendicular to flow tobe the floor joist. Thus, in an extreme flood the beams wouldnot be subjected to the full force of the storm water along theirmore exposed surfaces. This also reduces the potential forfloating debris to overturn the structure and places the lowestobstacle to flow above the floor beam.

Typically these beams are either built-up members(Figure 4-23) made from two "two-by" pieces of lumber (i.e., two2-by-10's or two 2-by-12's) or are solid members such as 4-by-10's or 4-by-12's. Solid beam members often are more difficultto obtain and are not always available at local lumber outlets.Solid beams do, however, offer higher fiber stress ratings inrelation to built-up beams of a similar nominal size. Therefore,a solid member is capable of larger load than a member builtup to the same dimensions. In many areas, "glulam" (glued-laminated)


Figure 4-24. Laminated beam connected to round timber pile using1/2-inch steel plate, hot-dipped galvanized after fabrication.

members, pressure treated, are available and suitable for usein place of solid members (Figure 4-24).

Residential structures in coastal high hazard areastypically range from 20 to 40 feet in the dimension parallel toflood flow. Since floor beams in those lengths are difficult tofind and hard to handle, it is common to use splices (Figure 4-23). Splices may occur in several places and should belocated directly over supports. Figure 4-23 also shows metaljoist anchors tying floor joists to the floor beam.

4.3.2.3 Joists and Rafters. A type of joist coming intoincreasing use is the wooden I-beam, manufactured withstructural wood flanges and a structural plywood web (Figure4-25). I-beam joists are lighter and can be produced in longerlengths than standard lumber; the thin

webs simplify the installation of wiring and plumbing the webs.Depths of the beams typically range from 8 to 20 inches (in 2-inch increments), with flange widths up to about 2-1/2 inches.Typically available lengths range up to 36 feet. Web stiffenersmay be required at bearing points. The individualmanufacturer's recommendations should be followed withregard to handling, web stiffening, and selection of size for arequired span.

In the velocity zone, cross bridging of all floor joists isrecommended due to the additional load factors related to thestructure's elevation. The elevation makes the floors(particularly the first floor) more accessible to uplift wind forces,as well as to the forces of moving water, wave impact, andfloating debris.

Cross bridging methods are included here becauselocal building codes may not require this desirable practice.The following are cross bridging recommendations:

• Nominal 1-by-3's at 8-foot-on-center maximum• Solid bridging same depth as joist at 8-foot-on-center

maximum.

4.3.2.4 Subflooring. Presently, two common methods are inuse for subfloor construction. These are the use of nominal 1-by-4 or 1-by-6 boards placed diagonally over the floor joist(either tongue-and-groove or square-edge with expansionspace between boards) and the use of plywood subflooring tocreate a floor diaphragm. When a plywood subfloor isplanned, guidelines for thickness and methods of attachment inrelation to joist spacing can be obtained from the "PlywoodConstruction Guide" of the American Plywood Association.

Due to the high-moisture environment, plywood used assubflooring material must incorporate exterior glue as theadhesive between each layer. Information describing


the glue system can be found in the grade stamp on eachsheet of plywood.

Subflooring is typically nailed directly to the floor joists.In coastal high hazard areas, nailing with annular ring nails ordeformed shank nails is recommended. These nails provideextra strength against pulling out when the floor system isexposed to loads other than gravity. Their holding ability issubstantially greater than common or galvanized nails whenstressed by wind, velocity flooding, or wave impact.

A system of nailing and adhesive application of plywoodwith tongue-and-groove joints along the long edges of thesheet avoids the need for blocking along these edges. Thissystem produces a more level floor and offers a strongerdiaphragm action to resist horizontal wave forces.

4.3.2.5 Studs. Most commonly used are 2-by-4 wood studs,16 inches on center. Recently, in areas where cold weather isanticipated, 2-by-6 studs have been used to permit 50 percentthicker wall insulation. Metal studs have been used for sometime on larger structures and are now becoming common onlow-rise, multifamily structures and, to a lesser extent, onsingle-family residences. The general configurations of metalstud walls are similar to the equivalent wood stud wall.

4.3.2.6 Wall Sheathing. Plywood is the most typical sheathingin use for exterior walls. The major advantages of plywood arethat it braces the wall framing to resist racking stresses andforms a continuous tie from floor beam to top plate whenproperly installed (Figure 4-26).

Plywood used for sheathing structures elevated notmore than 10 feet should be exterior grade and not less than15/32 inch thick. Nailing should be with 6d nails, spaced 6inches along the edges of the panel and 12 inches onintermediate studs.

Figure 4-25. Wooden I-beam.

Structures elevated more than 10 feet should besheathed with 3/4-inch exterior grade plywood, nailed with 8dnails, spaced 6 inches on edges and 12 inches onintermediate studs. Deformed shank or annular ring nails andplywood with exterior glue are recommended, as describedabove in the subflooring section.


Figure 4-26. Wall sheathing tie from roof to foundation.

4.3.2.7 Wall Bracing. Wood frame walls must be braced toresist wind forces, which can cause racking. Bracing of verticalwalls is typically a building industry standard, with severalmethods in common use. Wind forces present in the coastalhigh hazard environment lend more significance to this bracingthan in other areas. Additional wind loadings and lateral forcesof both moving water and wave action add to the total loads ona building and are particularly significant factors in bracingvertical walls.

Typical wall bracing methods are a let-in diagonal woodbrace, diagonal boards, and plywood (Figure 4-27). Onemethod similar to the let-in diagonal brace in common usetoday is a light gauge, galvanized steel strap nailed diagonallyto each stud at the outside corners of framed walls. Plywoodsheathing is the recommended method for wall bracing, andplacement of plywood sheets and nailing should followrecommendations of the American Plywood Association, usingannular ring nails. Plywood sheathing should cover the bottomplate and floor joist and the top plate of the wall, as shown onFigure 4-27. If the height from joist to top plate is greater than8 feet, panels of approximately equal size should be cut tospan the height, rather than using one 8-foot panel with a fill-inof a few inches. Plywood sheathing should be used at allcorners and should extend at least 4 feet in each direction fromeach corner.

4.3.2.8 Roof Details. Roof trusses are nearly universally usedtoday for roof framing, and can be purchased in either stock orcustom sizes and shapes. They are typically made from 2-by-4's and 2-by-6's, with the larger members used for longerspans. Older homes and some remodeling projects have usedthe traditional construction with individual rafters cut from 2-by-6's or 2-by-8's. Trusses and rafters are spaced at either 16inches or 24 inches, and sheathed with plywood. Heavierplywood is generally used for the 24-inch truss or rafterspacing. Trusses or rafters generally extend 1 or 2 feet overthe exterior walls at both the eaves


Figure 4-27. Corner wood bracing.

Figure 4-28. Gable/overhang failure.

and gable ends. Gable end extensions often use a hangingrafter that is essentially supported by the roof sheathing andtrim.

The shape and structural details of a roof are importantdue to the significant wind forces affecting this part of thestructure. Loss of all or part of a roof will result in significantdamage to the building and contents, and can result in the totalfailure or collapse of the entire superstructure. Even amongthose remaining intact, some roof types have been shown toprovide less obstruction to wind, exhibit better structuralintegrity, and be less prone to shingle loss and water leaksthan others.

Of the traditional sloping roof designs, hip roofs appearto perform best, as they do not present any flat


faces to the wind regardless of wind direction. These slopingfaces also add to the performance of the roofing material.

Gable roofs are the most common roof design andgenerally perform well, provided the gable ends of the roof areconstructed properly. Gable ends are vulnerable to damagedue to the significant wind uplift forces at the roof peak,compounded by structurally weak gable vent devices that oftenblow out in storms. Figure 4-2B shows a structure damagedby Hurricane Elena when the gable area failed.

Additional rigidity and stability of a gable roof framingsystem can be provided by installing 2-by-4 blocking on 2-footcenters between the roof rafters or

Figure 4-29. Porch overhang damaged by wind uplift.

trusses for about 8 feet at each end of the house. This will notonly strengthen the roof but will provide additional nailingsurface for roof sheathing materials. Using constructionadhesives in addition to nails when installing roof sheathingwill also improve uplift resistance.

Older flat roofs have not performed well in severestorms. Heavy rainfall causes ponding on the roofs, oftenresulting in water infiltration and interior water damage.Additionally, flat roofs are susceptible to uplift suction forcesfrom high winds, causing loss of roofing material.

Less commonly used designs have often not performedwell, due to overlooked areas of weakness. Gambrel or "barn"roofs, for example, have a mid-roof slope change at whichplywood decking cannot be lapped to strengthen the

4-30. Performance of braced piles at left vs. unbraced piles at right.


Figure 4-31. Performance of braced piles in foreground vs.unbraced piles in background.

joint. One gambrel roof observed by Rogers (1985) was welljoined at the wall connection around the exterior but failed atthe slope change and at the peak.

Roof overhangs and porches are common in coastalconstruction and require careful detailing when used.Overhangs on the water side of a structure provide a shadedseating area and an unencumbered view of the water. Ceilingand roof framing members are extended to provide structuralsupport for the overhang. If column supports are used, theyare commonly only lightly attached. Design of overhangs andporches is particularly important due to the large wind upliftforces on overhangs. Failures of overhangs 2 feet or less inwidth have been

Figure 4-32. Effect of Hurricane Frederic's wind and water forcespile system.

reported (Rogers, 1985), and damage to porches surveyed inthe same study was extensive. Figure 4-29 shows a largeporch overhang that was damaged by wind uplift forces.

4.3.3 Foundation Bracing

Bracing of the foundation piles that elevate coastal zoneresidences can be very effective in minimizing storm damage.As mentioned throughout this manual, connections of structuralelements are critical. Bolting--not nailing--is necessary at alljoints. The size of bracing members is important. Bracingmembers should be considered as critical to the structuralresistance of a foundation system as are the piles and the floorbeams. The sizing of bracing


Figure 4-33. Knee braces.

members and connections is discussed in more detail inAppendix B.

Figure 4-30 shows two adjacent elevated buildings. Thenearer light-colored building had bracing, which can be seenmore clearly in Figure 4-31. Note that wave action duringHurricane Frederic has scoured about 4 feet of sand fromunder these buildings, as can be seen by examining paint linesand discoloration on the piles. The light-colored building'sfoundation piles remain essentially vertical. However, itsneighbor did not have bracing, so the piles lean backward fromthe beach as is visible in Figure 4-31 and shown more clearlyfrom the east end of the building in Figure 4-32. It is alsopossible that the piles of the building in Figure 4-32 wereinadequately embedded.

Figure 4-34. Wood grade beam in both directions.

It must be emphasized that bracing members alone donot make an elevated residence storm resistant. Properlysized piles, adequate pile embedment, and good connectionsfrom the floor beams to the roof are all essential to making abuilding damage resistant. No weak links can be permitted incoastal construction, or storm resistance is reduced oreliminated.

It also should be noted that the use of bracing or gradebeams below the BFE is questioned by some designers,because these members obstruct flow and have a potential forincreasing erosion. Alternative methods for providingresistance to the lateral forces of wind and water are available.One such alternative is the use of battered piles around theperimeter of the structure; batter piles


are more difficult to install but have greater lateral resistancethan vertical piles. Another alternative, where a deck is to beconstructed, is to utilize the lateral resistance of the pilessupporting the deck to supplement the piles supporting thehouse itself. Strong structural connections are required toprovide this support, however.

4.3.3.1 Knee Braces. For residences elevated to about 8 or10 feet, diagonal bracing or knee braces can be effective insupporting the pile against the lateral forces of wind and water.Tables in the appendices of this manual can assist indetermining when bracing is required. But even whencalculations may permit the omission of bracing, it is goodpractice to strengthen the foundation system with somebracing. Knee braces, shown in

Figure 4-35. Slab undermined by storm scour.

Figure 4-33, can be effective in supporting the piles againstlateral forces, providing the brace is substantial with goodconnections. Suggested types and sizes of bracing membersand connections are included in Appendix B.

4.3.3.2 Grade Beams. An important part of bracing piles isproviding some support at the ground line. This may come fromtying the piles together in both directions with wood gradebeams, such as 8-by-8's firmly attached to the piles (Figure 4-34). Reinforced concrete grade beams, as part of a slab ongrade, are also suitable. Figures 4-35 and 4-36 show slabsthat were undermined by scour but remain in place to supportthe piles against lateral forces. It would be better to have theslab thickened at the edge and also extending out and aroundthe exterior piles, as shown in Figure 4-37.

Figure 4-36. Perimeter grade beam provided additional stability.


Figure 4-37. Slab on grade with thickened edge perimeter grade beam.

Some designers believe an underhouse concrete slabshould not be tied to piles or grade beams but purposelyallowed to settle with changes in ground elevation withoutaffecting the piling. This idea has some validity, particularly iferosion is expected. There is also a difference of opinionamong designers regarding the use of grade beams. Their usemay improve the lateral resistance of pile foundations;however, they may increase the wave forces on the foundationand the scour around the foundation. This manualrecommends the use of grade beams because they function tostrengthen the piling during the worst part of severe storms.Disadvantages of

Figure 4-38. Double level truss bracing system.

potentially increased scour are normally more than offset bythe stiffer foundation system.

4.3.3.3 Truss Bracing. When a house must be elevatedabout 10 feet or more above grade, and particularly when thedesign wind speed is 100 mph or greater, more substantialbracing may be necessary and it must be designedcarefully. Figure 4-38 shows a double-level truss systemconstructed perpendicular to the beach to resist water wavesand wind on structures elevated 12 feet or more above grade.Figure 4-39 shows a single-level truss bracing system that canbe used when a house is elevated to about 12 feet abovegrade.


Some details of truss member forces, size of members,and connection details are included in Appendix B. It isobvious that houses elevated to greater heights require morebracing and this increases the costs of the foundationsupporting system. Details of the member connection platesand number and size of bolts are also presented in AppendixB.

4.3.3.4 Shear Walls. Another kind of structure for resistinglateral forces is shear wall construction. A shear wall isgenerally made of reinforced concrete or reinforced concretemasonry. It acts as a deep beam in resisting forces in theplane of the wall. This type of construction is quite substantialand can be expensive relative to the types mentionedpreviously. If there is need to resist winds on the order of 100mph or more, and if water waves will act on the structure, thereis probably a need for a deep foundation. The shear wallsmust be firmly attached through grade beams to the piles. Thisbecomes expensive for single-family residences. However, formotels and apartment or commercial buildings the designprofessional may provide an economical combination of shearwalls and piles, possibly of concrete.

Shear wall concepts are described in Chapter 5;however, the details of such designs require an engineer andare not included in this manual.

4.3.4 Connections

One of the most critical aspects of building in a coastalhigh hazard area is the method of connecting the structuralmembers. A substantial difference exists betweenconventional connections in typical construction and thoserequired to withstand coastal forces and environmentalconditions. Construction in noncoastal areas must supportloads imposed by the weight of the building materials (deadload), weight of people and objects

(live load), and modest loads imposed by wind. Under normalconditions and with typical methods of attachment (toe nailingand anchor bolts), these loads acting downward throughgravity hold the building's structural framework together.

However, these loads represent only a portion of theloads imposed on any structural system in the high hazardcoastal zones. Additional forces are applied to these structuresby wind, velocity flooding, wave impact, and floating debris.The structural systems must be capable of withstanding theseloads and still support the structure and its occupants. Buildingcodes and common sense guide the and/or builder to firmlyconnect the roof to the walls, the walls to the floor joists, thefloor joists to the floor beams, and the floor beams to thefoundation.

Figure 4-39. Single level truss bracing system.


Figure 4-40. Floor joists insufficiently attached to floor beams byend nailing alone.

A vital feature of any acceptable anchorage system isthat it be continuous from foundation through floor framing,walls, and even roof framing in order that all portions of thestructural framework are mechanically tied together.

In the coastal area, anchorage devices are exposed notonly to additional loads but also to a corrosive and destructiveenvironment that can rapidly deteriorate and destroyimproperly protected materials. Extra precautions must betaken to ensure these devices will continue to perform over anextended time period. Though extra precautions in design,detailing, and workmanship are necessary, most appropriateanchorage methods are common to the carpentry trade.Basically, they include the use of bolts, metal straps, tie rods,mechanical

fasteners, and several other items that, when properlydesigned for coastal conditions, meet performance criteria.

Each of the previously discussed means of achievingelevation allows several successful methods for tying the mainfloor beams to the foundation. Some methods are unique to aparticular foundation system, while others apply to severaltypes of elevated foundations with little or no modification. Ananchorage system should meet the following criteria:

• Withstands all anticipated forces without structuralfailure.

• Continues to perform satisfactorily when materials

are wet, as well as under wetting and dryingconditions.

• Is protected to withstand corrosive conditions without

loss of strength for many years, preferably for thelifetime of the building.

• Is readily available and requires only normal

carpentry for installation.

This section of the design manual presents some of therecommended details for connections. Methods of anchoringthe foundation to the floor, floor to walls, and walls to roof arediscussed. Design tables in Appendix A include the averageuplift forces per foot of wall at various locations throughout thestructure. With this information the designer/builder is able todetermine the need for and type of connectors that provideadequate resistance to wind and water forces.

It is emphasized that simple nailing, especially toenailing, is not acceptable for wood construction in the coastalhigh hazard areas. Figure 4-40 shows floor joist and floorbeam connections that failed during Hurricane


Frederic. Generally, galvanized metal straps or other metaljoist anchors (with nails) or specially designed wood-to-woodconnectors are used. In joining wood members subject todynamic loads from wind, waves, or earthquake, it is importantto have strong connections. Bolts, lag bolts, or nails at rightangles to the direction of force (not toe or end nailing) are usedto provide the greatest resistance and reserve, or factor ofsafety. Sketches of various connections are included here forlocations of special concern.

4.3.4.1 Roof to Wall. Probably the most critical structuralconnections are those between the roof and walls. The roofconnections are critical because at that level there can berelatively large wind uplift forces combined with the dead loadof the roof itself. Also, these connections of roof structure tostud walls are limited in number; at most they can occur atevery roof rafter or truss. At lower levels in the house one canuse nailed plywood sheathing in addition to strap connectionson the stud walls to resist uplift forces.

It is most important that toe nailing alone not be used forconnecting roof rafters to the top plate of the walls. This isbecause the pull out resistance of toe nails is low, partially dueto the tendency to split the wood in the toe-nailed member. Anumber of galvanized metal connectors, such as those shownin Figures 4-41 and 4-42, have been developed that place thenails in a preferred orientation to best resist uplift and lateralforces. Manufacturers provide brochures with the necessarydesign information. The local design professional, builder, orbuilding supplier can provide information regarding thecapacity of various connectors when properly used.

The capacity of these connections directly depends onthe number of nails and their individual capacity to resist loadstransverse to their axis. Pull out resistance along the axis is notused; rather, the nails are placed at

Figure 4-41. Metal strap roof anchor.


Figure 4-42. Metal plate roof anchor.

right angles (perpendicular) to the wood members. Thecapacity of various size nails and other connectors to resist theforces in such connections is given in Appendix A. The numberof nails counted in figuring the total connection capacity of agiven joint is the lower number, which may occur on either sideof the joint. For example, in the connection of a roof rafter tothe top plate of a wall, if five nails are driven in the roof rafterand four in the top plate, the capacity of the connection islimited by the four nails on the lower side of the joint, into theplate.

Tables in Appendix A present the uplift forces that mustbe resisted at the roof-to-wall connection as a function ofdesign wind speed and the width and length of the house. Thedata are given as the average force per foot of wall. If the roofrafters or roof trusses are spaced at more than 1 2 inches oncenter (a common spacing is 16 inches on center), the upliftforces are calculated by the following formula:

rafter spacing in inches forces = (force per foot) x 12 inches

This provides the uplift force to be resisted by the connection ofroof rafter to top plate of the wall. For example, with 16-inchrafter spacing, the force per foot of wall would be multiplied(increased) by the ratio of 16/12, or 1.33.

The uplift forces and required connections at the exteriorends of the roof rafters or trusses described above and given inthe referenced design tables are based on only the exteriorwalls resisting uplift forces and no interior walls being tied tothe roof by straps or other metal connectors. To supplementthe exterior connections, it is also effective to have a positiveconnection from the ridge line of the roof down through interiorstud walls to the


floor system and subsequently the foundation. This isparticularly helpful in higher winds.

For the higher design wind speeds the uplift forces aregreat and may require special connections or, at the least,several of the standard connectors at each rafter. Also, roofrafters or trusses should be spaced not more than 16 inches oncenter unless special connections are provided. It is likely thata design professional, an engineer or architect, will be neededto design against these higher wind speeds.

Recommendations in this design manual are notsufficiently specific nor all-inclusive to cover fully all design ofconnections or other structural elements for design windspeeds higher than 140 mph. However, such high windspeeds are limited to a small portion of the U.S. coastline.Moreover, the information in this publication can be ofassistance to the design professional even in this most severewind environment.

4.3.4.2 Wall to Floor Joists. Exterior walls are used astension members to transfer wind uplift forces at the roof downto the resistance provided by the foundation of piles or spreadfootings. The plywood sheathing should be well nailed into thetop plate of the stud wall and at the bottom into the floor joistsand band beams. It is not adequate merely to nail the plywoodsheathing to the bottom plate of the stud wall because thebottom plate nails to the floor joists may pull out. If thesheathing does not extend to the bottom of the floor joists, it isnecessary to use galvanized metal strap connections from theexterior wall studs to the floor joists. The capacity of theseconnections depends on the number of nails used. Asmentioned above, manufacturers' brochures are used bydesigners and builders to ascertain the connectors' capacityand thus the spacing required.

4.3.4.3 Floor Joist to Floor Beam. Below the first-floor level, apositive connection to resist wind uplift forces is requiredbetween the floor joists and the floor beams. The necessity forpositive connections at this and other levels of a coastalstructure was shown in Figure 4-21. Hurricane wind upliftforces raised the structure slightly, stretching the metal straps,which then bulged as shown when the winds subsided. Metalconnectors have been developed by manufacturers thatprovide efficient nail arrangements to resist the uplift forces(Figure 4-43).

A good wood connection detail has also beendeveloped (Figure 4-44). The advantage of this detail overother methods for anchoring these members together is in theuse of wood rather than corrosion-susceptible steel as theconnecting unit. Further details on wood joist anchors areavailable in a pamphlet from University of North Carolina, SeaGrant Publications (1984). Properly treated wood blocking,with annual maintenance and preservative applied to cut ends,will perform as designed for a substantially longer time thansteel connectors. As mentioned earlier, the number and size ofnails into the floor joist or floor beam governs the uplift capacityof the connection.

4.3.4.4 Floor Beam to Pile, Post, or Pier. A major connectionis made between the floor beam and its support. In manylocations, this support is a pile embedded some distance intothe ground and extending far enough above the ground toelevate the bottom of the floor beam above the BFE. The piles,as described previously in this chapter, are frequently taperedround wood members with a top diameter (at the floor beamlevel) of about 11 inches or more. Many builders prefer to usesquare, rough-sawn piles, either 10 by 10 or 8 by 8 inches insize. Where the lateral forces and potential for erosion due toflood waters are less severe than near the ocean beach, woodposts or reinforced concrete masonry unit piers may be used.


Appendix A presents the uplift capacity of various sizebolts used to connect through floor beams to piles or posts.Note that washers should be used under all nuts and boltheads bearing directly on wood. Figures 4-43 through 4-52show typical connections, including metal straps on the sidesof floor beams and piles and floor beams notched into thesides of piles. Care must be taken in designing andconstructing these connections.

For the steel plate connection illustrated in Figure 4-52, a 1/4-inch-thick steel plate is inserted into the top of thepile. The plate may be predrilled for the bolts and galvanizedafter drilling for maximum corrosion protection. A built-upbeam is then bolted through the plate at each pile as indicated.This connection provides a much stiffer joint and reduces the"pull out" potential as compared to a bolt through wood only.This detail would be particularly effective in areas where upliftforces from extremely high winds are likely. An as-builtexample of a steel plate connector is shown in Figure 4-24.The 1/2-inch-thick connector was hot-dipped galvanizedafter fabrication.

Figure 4-53 shows a double-notched pile at a houseunder construction. Only 25 percent of the pile area remains;with water impact, the pile likely would fail at the base of thestub. Generally, the pile should be notched only enough toprovide a shelf for supporting the beam, and total notchingshould not exceed 50 percent of the pile cross section. Figure 5-54 shows weak connections between piles and floorbeams that failed during a storm. Figure 4-55 shows a steelreinforcing bar that was used unsuccessfully to tie floor beamto pile. Connections of floor beams to masonry piers areillustrated in Figures 4-56 through 4-59.

Other methods not shown here are not necessarilyexcluded, but the advice of a qualified professional should besought before their use.

Figure 4-43. Metal hurricane clips.

Figure 4-44. Wood joist anchors.


Figure 4-45. Wood joint anchor installation.

Figure 4-46. Double notched spacedbeam to pile connection.

Figure 4-47. Connection for built-up beam.

Figure 4-48. Connection at single notched pile.


Figure 4-49. Spiked grid connection.

Figure 4-50. Mortised gusset connection.

Figure 4-51. Notched pile with gusset.

Figure 4-52. Steel plate insert.


Figure 4-53. Over notched wood pile.

Figure 4-54. Failure of pile connections at floor beamand at knee brace.

Figure 4-55. Steel reinforcing bar inadequateto attach floor beam to this pile.


Figure 4-56. Masonry pier - strap anchorconnection.

Figure 4-57. Masonry pier - bolt throughbeam connection.

Figure 4-58. Masonry pier - beam seatconnection.

Figure 4-59. Concrete masonry unit piers connected by galvanizedclips to floor beams.


4.3.5 Breakaway Walls

Elevation of a structure on a properly designedfoundation reduces the potential for water damage fromflooding. When the space below the lowest elevated floor ismaintained free of solid obstructions as well, the potential fordamage from waves or debris is further reduced. In recognitionof the desirability of using the sheltered space beneathelevated structures, NFIP regulations permit certain limiteduses of enclosed space below the BFE. Uses such as parkingof vehicles, building access, or storage are permitted, as longas the walls of any enclosures are designed as "breakaway."A breakaway wall is a wall that is not part of the structuralsupport of the building, intended through its design andconstruction to collapse under specific lateral (wind andwater) loading conditions without causing collapse,displacement, or other structural damage to the elevatedportion of the building or supporting foundation system.

To ensure that breakaway walls withstand forces fromwind and everyday use, yet collapse under storm conditions,current NFIP regulations require that a breakaway wall shallhave a design safe loading resistance of not less than 10 andno more than 20 pounds per square foot. The regulationsallow walls with a greater loading resistance under certainconditions, and when the design is certified by a registeredprofessional engineer or architect. The need for greaterloading resistance could be a result of design requirements orrequired by local or State codes. In either case, the designermust certify both of the following:

• Breakaway wall collapse shall result from a waterload less than that which would occur during thebase flood.

• The elevated portion of the building andsupporting foundation system shall not be subjectto collapse, displacement, or other

structural damage due to the effects of wind andwater loads acting simultaneously on all buildingcomponents (structural and nonstructural).Maximum wind and water loading values to be usedin this determination shall each have a I percentchance of being equaled or exceeded in any givenyear (100 year mean recurrence interval).

The uses that owners make of the sheltered spacebeneath elevated homes has historically led to a wide range ofenclosure designs, from insect screening to heavyconventional walls.

Screening and lattice work are the lowest strengthenclosures and when properly constructed can serve theirintended function with little effect on the structural loadings onthe house. These walls provide partial protection andsecurity for items stored under an elevated structure. Latticework is often used for architectural purposes, as shown byFigure 4-60, to visually tie the house to its surroundings.

While screening and lattice provide some protection forvehicles and stored items from salt spray and otherenvironmental conditions, full protection from the elements canonly be provided by a solid wall. Walls providing thisprotection from the elements can be designed to withstandcertain wind and water loads and to break away or fail whendesign loads are exceeded.

Construction of walls stronger than the structural frameof the building was designed to withstand will jeopardize theintegrity of the structure under storm conditions. Thisstrengthening of the walls (i.e., by using extra fasteners) so thatthey do not break away before damaging the structure mayoccur during initial construction or as a result of latermodifications by the


Figure 4-60. Lattice enclosure under elevated structure.

owner. Strong walls would allow excessive scour anddamaging wave runup during severe storms, while weakerwalls will break away before these effects become significant.

In accordance with the current NFIP regulations, whichprovide the specific guidance stated above, this manualrecommends that only screening, lattice work, or lightbreakaway walls be constructed below residential structures,unless specifically designed by a registered professionalengineer or architect. As Figure 4-61 (of storm damage duringHurricane Alicia) shows, structures can survive major stormsrelatively intact when ground-level enclosure walls breakaway.

4.3.5.1 Breakaway Wall Designs

Screening. One means for partially or fully enclosingthe area below the BFE is installation of metal or syntheticscreening to provide insect protection and minimal security.Screening is fastened to pilings by nails, staples, or nailedmoldings, and will fail under small loads imposed by wind,velocity water, or moving debris. Replacement costs are verylow.

Lattice. Lattice work can be used for minimalenclosures beneath an elevated structure. If fabricated usinglight materials and properly connected to the foundation,lattice will break away under small water loads. No portion ofthe lattice wall should overlap the piles supporting the elevatedstructure. The wall should be butt-connected to the piles.

Figure 4-61. Storm damage during Hurricane Alicia.


Figure 4-62 shows a lattice wall design using lightcrisscross lattice that is available premade and sold in 4-by-8-foot sheets. As shown in the figure, a 2-by-4 top plate ispermanently nailed into the floor beam and a 2-by-4 bottomplate is permanently attached to the grade beam. Wall studs (2by 4's) are toe-nailed into the top and bottom plate using two8d nails. The premade lattice (1/4 by 1-1/2 inches) is nailed tothe frame using galvanized nails. This wall will have aworking strength of approximately 10 psf and will fail as aresult of material failure in the lattice.

Lattice walls that use larger (i.e., 1-by-4 to 1-by-8)boards have greater inherent strength than crisscross lattice,even when the open/solid space ratio is the same. While thelight lattice wall will fail in the lattice material even if the frameis overbuilt, the stronger lattice wall likely will fail at theconnections under a much higher loading. Because of thedifficulty in accurately predicting the material strength ofheavier lattice walls, it is recommended that the wall bedesigned to fail at the connections. The wall attachmentconcept and nailing systems for these heavier lattice walls arethe same as described below for wood stud walls.

Wood Stud Walls. Most solid breakaway walls underelevated single-family residences are of wood studconstruction. A wood stud breakaway wall design is shown inFigure 4-63. Permanent top and bottom plates (2 by 4) arerespectively nailed to the floor beam and grade beam withpermanent high strength fasteners or nails. A 2-by-4breakaway frame that consists of studs (toe-nailed with two 10dnails) and top and bottom nailer plates is attached to thepermanent top and bottom plates with nails sized and spacedto give the required lateral capacity. Care should be taken thatthe 10d nails do not penetrate into the permanent top andbottom plates. The frame is then covered with plywood or othersheathing that is either

Figure 4-62. Lattice wall.


Figure 4-63. Wood stud breakaway wall.

butted to the piles or allows for a small clearance. Thesheathing must not overlap the permanent plates or thepiles.

It is planned that the walls would be placed as a unit andthen nailed as prescribed at the top and bottom to permanentnailer plates already securely attached to the floor system andgrade beam or slab. The permanent nailer plate is an essentialcomponent of the wall system and provides a predictable pointof attachment for the wall. The wall is designed to fail at thenailed connections to the permanent nailer plate. Varioussizes and spacings of the nails could be used to achieve thedesired resistance to lateral load. The capacities of 8d through16d common nails in shear are shown on Table A-11. Table A-12 provides a nailing schedule for normal combinations ofbreakaway wall height and pile spacing to result in a wall witha design safe loading resistance between 10 and 20 psf.

Metal Stud Walls. Metal studs, which have beencommonly used on larger structures, are now being used morefrequently on low-rise multifamily structures and to a lesserextent on single-family residences. Unless properlygalvanized, metal studs will corrode rapidly in the coastalenvironment.

Figure 4-64 shows a light-gauge metal stud wall design.The wall attachment concept and nailing system is the same asthe wood stud wall design discussed above. Fastenercapacities for the self-tapping screws commonly used to attachthe metal stud wall to the more firmly secured wood nailer alsoare shown on Table A-11, and a fastener schedule for commonwall height/pile spacings is shown on Table A-12. Note thatthe failure capacity of metal stud wall systems can be moreaccurately determined than for wood systems and a lowersafety factor can be used.


Masonry Walls. Full masonry walls for enclosuresunder structures are common in larger buildings, though insouth Florida they are used in all types of structures. Masonrywalls can be constructed either unreinforced or reinforced.

Figure 4-65 shows a wall that can be constructed with orwithout reinforcement. The pins at the top of the wall are tomaintain the stability of the wall under design wind loadings.The sides and top of the wall must not have bonded contact tothe structure. If unreinforced, the wall will likely fail in shear inthe mortar prior to shearing the retaining pins. Anunreinforced masonry wall with mortared joints, constructed asshown in Figure 4-65, will have a design safe loadingresistance of about 20 psf (assuming an 8-foot-high wall and1,800 psi Type S mortar), and would meet NFIP criteria forbreakaway walls.

If reinforced, the wall is restrained by dowel pins at thetop and reinforcing bars at the bottom. The placement of dowelpins and reinforcing bars permits a more accuratedetermination of the strength of the wall before failure occurs.Failure will begin with the pins shot into the main structurerather than with the mortar in the wall. This is due to thereinforcing. Once the pins fail, the wall will cantilever with thereinforcing bars at the bottom of the wall, providing additionalresistance to failure until the wall's capacity is reached. Thelateral capacity of the reinforced masonry wall will varydepending on the size and spacing of the reinforcing bars.Because the loading resistance of a reinforced masonry wallexceeds NFIP criteria, such walls should be used only whendesigned by a registered professional engineer or architect.

4.3.5.2 Design Considerations for Breakaway Walls. Anumber of design considerations are required when a solidenclosure wall, or even a partially open wall, is placed

Figure 4-64. Light gauge metal stud breakaway wall.


Figure 4-65. Masonry breakaway wall.

beneath the BFE. Governing the design process are thefollowing primary concerns:

• Enclosure walls must be constructed to withstandloading forces from moderately high winds, with anormal factor of safety. At a minimum, this loadcapacity would be the design wind load required bythe local building code. If the code-required designload is greater than the 20 psf allowed by NFIPregulations, the code should prevail.

• At high wind speeds and/or under water loading, the

wall must fail without causing damage to thefoundation or superstructure, either from lateralloading or wave runup/ramping into the rest of thestructure. This is the failure load or ultimate loadcapacity of the wall.

• For small enclosures or relatively close pile

spacings, it can be assumed that all piles within theenclosed area resist wind and water loads againstwalls below the BFE. For larger enclosures or widerpile spacing, only a limited number of piles can bebrought into action to resist lateral loading. Additionalbracing will be required for front row piles supportingthe wall receiving water loading.

• Solid enclosure walls below the BFE increase

potential for wave scour at grade beams and piles,particularly for stronger walls.

Wind Forces. Design for breakaway walls mustconsider wind forces on the house superstructure, which aretransmitted to and resisted by the foundation system, as well aswind forces on the breakaway wall, which are also transmittedto the house frame and foundations until the lateral resistanceof the wall or its fasteners is exceeded.


The wind load on a breakaway wall is considered to be appliedas a uniform load per square foot of vertical wall, which can beresolved into a resultant load applied along the fastenededge(s) of the wall.

Wind direction during storm events is often fromoffshore. However, in design of houses and breakaway walls,the wind should be assumed to blow potentially from anylateral direction relative to the house.

Water Forces. In addition to wind loads on the entirehouse, water loads on the portions of the structure below theBFE must be considered. These water loads include bothsimple hydrostatic pressure from a slow rise in stillwater depthand the forces of waves against the structure. The BFE for agiven area is the maximum height of stillwater plus wavesabove which a structure must be elevated, as illustrated inFigure 4-66a. When the area below the BFE is obstructed by awall, wave runup occurs on the wall. In this case, illustrated inFigure 4-66b, water reaches the BFE on the wall when thestillwater plus unobstructed waves remain well below the BFE. To prevent water damage to floor beams and suspendedutilities, breakaway walls should be designed to fail when orbefore wave runup reaches the BFE.

Structural Considerations. Designing for ultimatecapacity requires that the breakaway wall strength at failure bepredetermined, and that sizes and spacings of components beselected to assure failure at the desired location and loading. Itis not sufficient for enclosure walls to merely break away; theymust do so predictably.

The best enclosure wall designs use simple constructiontechniques, materials, and connections. Recommendedbreakaway wall concepts that meet these requirements weredescribed in the previous section.

Figure 4-66 a&b. Effect of enclosure walls on waves.


Connections. Breakaway walls should be constructedsuch that they are fastened to the structural frame on twoopposite ends only, either top-and-bottom fastening orfastening on each side. Under lateral loading they will thenbend in one plane only, stressing the connectionsapproximately equally. Top-and-bottom connections arepreferred and are recommended in this report for threereasons. First, while wind forces are essentially uniform over aflat wall, water forces will be concentrated at the bottom of thewall as the water rises. It is appropriate structurally to havethe lower edge remain firmly connected at lower water levelsand its connections reach their ultimate capacity uniformlyacross the bottom as the water rises. Second, stud walls aregenerally installed with the studs vertical, and should be flexedalong the length of the studs. Third, and most importantly,loads on breakaway walls need to be directed into the floorsystem of the first elevated floor, in order to assure distributionof the loads to adjacent piles. Side fastening would direct toogreat a portion of the total load into the piles on the loadedwall.

Included in the above considerations is the basicpremise that, unless designed by a registered professional,breakaway walls should be proportioned such that wallstrength is governed by the wall's connections to the pilefoundation/grade beam system and to the bottom of theelevated floor system. Experience has shown that it is morereliable--and much easier--to design connections to fail at aspecified level of force rather than have the wall material failinternally.

Working/Ultimate Strength of Fasteners. The safetyfactor that is used in design depends on the materials usedand the accuracy with which one knows the design loads andmaterial properties. To compensate for these uncertainties,working (or safe) load capacities of materials and connectionsare generally taken

conservatively. The "design safe loading resistance" referredto in the NFIP regulations corresponds to a working capacity.The collapse or ultimate resistance of a wall would be higher,corresponding to the factor of safety appropriate to the wallmaterials and fasteners used. Table A-10 provides workingand ultimate strength values for fasteners that could be usedfor breakaway wall connections.

It is important to note the effect of the different of safetyon the overall safe and ultimate capacities breakaway walls.That is, walls of different construction, designed to the samestandard for safe capacity, will have different ultimatecapacities because of their differing factors of safety.

Distribution of Wall Loads. For breakaway walls, windand water loads cannot be distributed equally among the pilesunder a structure. Compared to the upper superstructure, thefloor beams and joists are an insufficiently stiff system fortransfer of lateral loads over any distance. It is thereforereasonable to limit load distribution to among those piles in theenclosed area, and to further limit distribution if piles are widelyspaced. A breakaway wall connected to a well-constructedfloor system and to a grade beam system can transfer water orwind loads on the wall laterally for about 8 feet maximum.Therefore, only piles that are within an enclosed area, andwithin 8 feet of the outside walls of such enclosed space, mayshare the lateral loads equally with other piles within theenclosed space.

For wider pile spacing perpendicular to the direction ofloading, only those piles supporting the loaded breakawaywall, plus those piles attached to the breakaway walls parallelto the direction of flow, carry the lateral forces. This providessome extra margin of safety if the floor system does resist thepile deflection and distributes the


forces to other piles, which are not directly subjected to thewater loads. The application of these recommendations tothree example pile configurations is shown in Figure 4-67.

It must further be noted that, in general, water loadingscan be assumed to act in a direction perpendicular to theshoreline, but considerable variation can occur. Wind canoccur from any direction. Therefore, the determination of thenumber of piles that would resist lateral loads from wind orwaves should include consideration of loading bothperpendicular and parallel to the shoreline. This would betrue particularly for structures that are not aligned normal tothe general orientation of the shoreline.

Bracing Considerations for Breakaway Walls. For anyhouse with enclosure walls below the BFE, there is anadvantage of having floor beams span in the direction of thewater flow. This is because the floor beams can assist thefrontmost piles, laterally loaded by water against a wall, totransfer the load back to the tops of piles several rows backfrom the breakaway wall. If the floor beams run transverse tothe direction of water flow, as shown in Figure 4-68, acompression strut (an 8-by-8 or three 2-by-12's, for example)should be placed between the tops of all piles assumed tocarry the water loads.

A similar approach should be taken for grade beams.Typical practice is to construct grade beams around thebuilding perimeter only. Grade beams should also beinstalled on the interior of a building in both directions for allpiles considered to carry the breakaway wall load. For theexample structure shown in Figure 4-68, thisrecommendation would require installation of four interiorgrade beams. These beams will also serve to provide propersupport for attachment of the interior breakaway walls.

EXAMPLE A12' SPACING OF PILES

EXAMPLE B8' SPACING OF PILES

EXAMPLE C10' SPACING OF PILES

Figure 4-67. Pile spacing effect on distribution of wall loads.


PREFERRED DIRECTIONFOR FLOOR BEAMS

Compression struts as shownare required when floorbeams are parallel toshoreline

Figure 4-68. Bracing consideration.

Knee braces have the desirable characteristic ofstrengthening both the individual piles to which they areattached and the structure in general. The overall need forknee braces or other bracing is determined using Table A-4.The strengthening effect of knee braces on individual pileswould be especially important for front row piles supportingbreakaway walls subject to water loading, and would assist thepiles in resisting shear forces. The front row piles should beconsidered separately from the overall structure's need forbracing, and knee braces in the direction parallel to expectedwater forces are a minimum requirement for front row piles thatsupport breakaway walls. Where knee braces or other bracingis used in the same plane with breakaway walls, care shouldbe taken that the bracing does not impede the breakawaycapability of the walls.

4.3.6 Utilities

Structures in the coastal high hazard areas arecommonly served by combinations of electricity, water supply,sanitary sewerage, gas (natural or bottled), and telephone.Typical installations for these utilities expose them to potentialdamage from flooding and wave impact. In the case of anelevated first floor, the connection from an underground utilityline to the floor above further exposes the line to possibledamage and/or contamination by flooding and wave action.Underground services are also susceptible to damage whenscour and erosion of the protective soil cover leave themexposed during flooding.

Disruption of these utility services can leave a structureuninhabitable following a storm. Damage to these systems cancreate many dangerous conditions, such as contamination ofdrinking water, discharge of effluent from sewer lines, ruptureof gas lines, and fires and/or shock from damaged electricalsystems or frozen electrical meters.


Recommendations for the protection of these systems arebased on the following criteria:

• Major utilities and mechanical equipment shouldbe protected from inundation by the base flood.

• Utility connections and underground services must

be capable of withstanding forces imparted by avelocity flood condition, without damage orcontamination of other resources.

• The structure should remain habitable following

flooding, with necessary systems for habitation(water, sanitary sewer, and electric power) operatingproperly.

The most vulnerable section of any utility line is theportion between the incoming underground service and theentrance to the elevated first floor. This section is exposed forthe full height of elevation and thus is susceptible to damage.

A minimum amount of protection can be obtained bylocating these utility risers on the sides of interior piles or piersaway from the ocean front. This will minimize damage fromwave impact or floating debris. A more secure method is toplace all vertical utility lines within a protective, floodproofenclosure attached to the side of interior piles or piers awayfrom the beach. This enclosure should be securely fastened tothe pile and should not be more than 2 feet wide unlessdesigned by a professional engineer or architect. Such anenclosure will impart additional loads to the pile to which it isattached.

For an enclosure larger than 2 feet, the supporting pileor piles must be designed to withstand the additional loadsbeyond the maximum design loads for which the pile system isdesigned, requiring either increased pile size or bracing. Inaddition, potentially damaging effects of wave runup on thefloor beams adjoining the enclosure at maximum waveelevation must be considered. Scour around the base of alarger permanent enclosure will also be increased and mayrequire deeper pile embedment.

The incoming power service should be firmly secured tothe structure, but fastened in such a manner that if the wires arepulled from the house, the building's protective envelope is notdamaged. Several cases have been observed where thedowned wires have removed sheathing, allowing rain entry.The entry cable should then be connected through the utilitycompany's meter system, above the BFE. However, thisrequirement is often in direct conflict with the power company'spolicy regarding the reading of meters and their location. Ifelevated connections are not possible, the utility line should beconnected within a waterproof enclosure. All distributionpanels or other major electrical equipment should also belocated above the BFE. Branch circuit wiring should be fedfrom the first-floor ceiling downward to keep wiring out of thefirst floor and above expected flood water heights.

All mechanical equipment (furnaces, hot waterheaters, air-conditioning, water softeners) should beelevated above the BFE. Figure 4-69 shows an elevated airconditioning unit. Where possible, heating/cooling units on theexterior of a structure should be located on the landward side,where they would be sheltered from salt spray but exposed torainfall that will rinse accumulated salt. Heating and/or coolingsystems using ductwork to carry tempered air should beprovided with emergency openings at the lowest elevationsand a minimum slope on


horizontal duct runs, allowing the system to drain should itbecome submerged.

Elevation of utilities to protect them from water damageis becoming an established practice. Elevated utilities such asexterior heat exchangers and roof-mounted solar heatingequipment are also particularly vulnerable to wind damage. Many standard units have mounting fasteners that areinadequate for coastal areas. Straps, tie-bolts, or otherauxiliary hold-downs should be installed if in doubt.

4.3.7 Wind and Storm Protection of Interior

It is estimated that loss of window glass caused a largeportion of the wind and wind-driven rain damage fromHurricanes Alicia, Gloria, and Elena. Even moderate storms orroutine high winds can cause large losses of glass in buildingsalong the coast. Many beach residences have large openingswith glass facing the beach that are susceptible to suchdamage. Broken glass or other unprotected openings mayallow rainwater, seawater, and high winds to enter thestructure, all of which can increase losses. Water damage mayruin furniture and carpets and eventually damage finishes andstructural members.

Wind allowed into an elevated structure increases theuplift load on the structure as it applies pressure to the ceilingand wall surfaces. Many structural failures such as that shownin Figure 4-7 have resulted from window and door failures andsubsequent loss of the roof and interior walls from windpressure. Therefore, openings in a building should havespecial protective coverings available that can be quickly andeasily used when storms approach and when the building isnot occupied during the off-season.

Figure 4-69. Heating/cooling unit elevated to above the BFE.

Several features may be incorporated into an elevatedstructure's design that offer protection from wind, moving water,and debris during a storm. Most of these features involve ideasthat are simple to execute, are normally associated with beachhouses anyway, and add relatively little, if anything, to the cost.These also can offer tighter security during the off-season forresidences not occupied on a year-round basis.

4.3.7.1 Window Selection. Coastal structures are commonlyconstructed with large window areas on the water side tomaximize the view from the interior of the structure. Double-and multiple-section sliding glass doors often extend acrossthe entire front of a house. These arrangements have beenfound to leak excessively in the


wind-driven rain of coastal storms and are vulnerable todamage from windborne debris. Improved window designsnow available greatly reduce water infiltration, and highly ratedwindows should be specified for all new construction orwindow replacements. Generally, for both strength and waterresistance, multiple-panel sliding glass windows should beavoided, and individual panel widths should be limited to 3feet. Door and window openings limited to no more than 30percent of a wall's area are recommended.

4.3.7.2 Operable Shutters. Exterior shutters over windowopenings protect against wave and wind action whilesimultaneously providing vandalism protection during the off-season. Shutters may take several forms.

Figure 4-70. Shutters for window protection.

Figure 4-71. Plywood sheets used for window protection.

For small openings the traditional wood louvered shutterwill offer some protection. Additional protection may berealized by using 1/2-inch plywood attached to the back of theshutter, which will take the direct forces from the storm (Figure4-70). These shutters, when secured from inside, offer securityas well. This method allows coverage of fairly large areas ofcontinuous glass and of sliding glass doors.

Some form of protection of glassed openings is stronglyrecommended for all coastal structures. Precut plywoodpanels can be fabricated and stored onsite. There is generallysufficient warning of impending storms to allow the 1 or 2 hoursrequired to install protective panels. Figure 4-71 showsplywood panels being removed from a house with


a large glassed area following a hurricane. As an alternative,manufacturers now offer permanent roll-up protective panelsthat can be manually or electrically deployed. Some are evenoffered with sensors for automatic deployment. Manualoverrides should be provided for any system, however, for usein the event of a power failure. Also, panels of any kind shouldnot block emergency egress from the structure.

4.3.7.3 Gable and Eave Vents. Attic ventilation is important toboth a house and its occupants, to remove trapped heat andhumidity. Gable vents have been found to be leak-pronebecause standard designs that provide adequate protectioninland are vulnerable to wind-driven rain in coastal locations.Similarly, inexpensive wind-turbine attic vents have failedduring storms, leaving large holes in the roof. Selection of atticventilators should be performed carefully, checking both thewind rating and the overall quality of construction andconnections.

Customized units should be prepared where necessary.One owner reported by Rogers (1985) custom built louveredvents with a louver width twice what is available as standard;even so, he was able to reduce rain infiltration substantially butnot eliminate it. Eave vents provide ventilation of under-roofspace while being less vulnerable to wind and wind-drivenrain than vents installed on flat vertical surfaces. These ventsare typically made from aluminum mesh, backed by aluminumscreen. Heavy gauge or coated metal or plastic vents arepreferred.

4.3.7.4 Roofing Materials. Experience has shown thatalthough loss of roofing material in high winds (as shown inFigure 4-72) may cause little direct structural damage,subsequent water damage to the house may be substantial.Use of quality materials, such as self-sealing, heavyweightshingles, is a prudent investment.

4.3.8 Maintenance

All structures exposed to the elements deteriorate withtime; this process is greatly accelerated in the coastalenvironment. Deterioration of structural members, fasteners,vents, utilities, and other components may go unnoticed untilfailure occurs during a storm.

The best defense against deterioration is to use qualitymethods and materials during initial construction. Rot-resistantor pressure-treated lumber should be used at all directlyexposed locations, and conventional lumber should be fieldcoated with stain or other preservative. All exposed steelshould be hot-dipped galvanized, preferably after fabrication. Stainless steel should be substituted where possible. Weather-resistant fixtures should be used if available. If possible, allunderside beams and floor joists of an elevated house shouldbe protected by sheathing.

Regular, at least yearly, inspections should be made ofany coastal structure, with particular attention to structuralconnections. Items that should be inspected include, but arenot limited to, the following:

• Pilings . Inspect each piling from top to bottom forevidence of rot or damage. Select a fewrepresentative piles and dig down 1 to 2 feet toobserve the soundness of the piles. Check all kneebraces and other bracing.

• Pile-Floor and Beam-Floor Joist Connections . Check

tightness of representative pile-beam bolts, andinspect all other exposed metal fasteners orconnectors for corrosion. Replace or supplementany that show deep-seated corrosion. Typicalmaximum life of fabricated metal connectors underexposed conditions is 5 to 10 years.


Figure 4-72. Loss of roofing in Hurricane Elena.

• Operable Shutters, Lift-Up Decks, and Other Protective Devices . A "dry run" of all devices thatmust be manually activated to provide protectionshould be conducted at least once each season. If astructure is to be unattended for an extended period,all protective devices should be in place beforeleaving. Operate all shutters and lift-up devices, andlubricate joints and locks if appropriate.

• Attic Vents, Attic Fans, Chimney Covers . Check for

loosening, corrosion, or structural cracking that couldfail under high winds, giving water a pathway to thehouse interior.

• Heating/Air Conditioning Units . Units should be

periodically hosed with freshwater to remove saltaccumulation. When not used for extended periods,they should be rinsed, allowed

Figure 4-73. Corrosion of cast iron sewer trap in coastal environment.

to thoroughly dry, coated with a light aerosol oil, andcovered with plastic sheeting or other watertightcover.

• Metal Chimneys . Use of insulated metal chimneysfor fireplaces and stoves is widespread, and mostchimneys have galvanized exteriors, internalspacers, and caps. Although most chimneys areboxed in with wood sheathing, salt spray and wind-driven rain can enter through the top cap area.Inspection of the chimney should be performed atleast annually in conjunction with chimney cleaning.

• Utilities . Inspect all tie-downs, supports, and hangers

and the general condition of all exposed wiring andpiping. Figure 4-73 shows a sewer trap that shouldbe replaced before a leak develops.

Larger Structures 5-1

Chapter 5

LARGER STRUCTURES

In the first edition of this manual, emphasis was placedon the design of light, single-family residential structures. Inupdating and expanding this second edition, it is felt that a briefdiscussion of larger, more substantial buildings would be ofinterest and benefit to design professionals, potential buyers ofcondominium units, building officials, and others interested inthe design and construction of larger mid- to high-risestructures located in coastal high hazard areas. Thisdiscussion will deal generally with more substantial buildingsin excess of two stories in height. Those considered willinclude the mid-rise structures from three to seven stories andhigh-rise structures of eight stories or more. Buildings of thisnature designed for construction in coastal high hazard zonesare subject to the same devastating forces of nature--both windand water--as the smaller structures discussed at greaterlength in this manual.

5.1 GENERAL DESIGN CONSIDERATIONS

Most coastal area design criteria apply equally to bothlow-rise and mid- to high-rise structures. The intention ofregulatory criteria is to promote safe construction at reasonablecost, while protecting the shoreline area to the maximumpractical extent. General siting criteria discussed in Chapter 3,such as setback and dune preservation regulations, apply tomid- and high-rise structures.

Ground level obstructions to flow are also subject torestriction. Enclosures for habitation at grade are prohibitedbeneath mid- and high-rise structures in coastal

high hazard areas, and nonessential enclosures such asentrances, lobbies, parking areas, and storage areas musthave breakaway walls. Below-grade construction (as forparking) is prohibited because of the flooding potential.

In addition to regulatory criteria, many features of coastalarea design and construction have evolved throughexperience and should be considered when developing plansfor a coastal property. For example, thicker concrete coverover reinforcing steel is commonly used in coastal areas toprovide added corrosion protection to the steel. Salt air hasbeen found to defeat the "weathering" feature of special steelthat can be left exposed in inland areas, by causing excessiveweathering and flaking of the weathered surface. Additionally,the likelihood during their useful lives of inundation and/orwave damage to decks, bulkheads, swimming pools, andother ground level construction should be anticipated.

Design of mid- and high-rise structures in coastalregions must consider forces from wind or water that producevery large lateral loads, due to the large surface areas of thesestructures. These loads tend to dictate the most appropriatestructural systems. The foundation and framing systems mustbe able to cost-effectively resist the lateral forces from wind andwater as well as the vertical forces from dead and live loads.

In high-rise structures, lateral forces created by wind aregenerally far greater than those generated by water. Windpressures therefore provide the governing design parametersfor larger structures. Even broken or breaking waves do notgovern the design of the primary structural frame of a high-risebuilding when compared to those forces created by hurricaneforce winds on large surface


areas. These are somewhat different conditions from thosegoverning the design of low-rise structures, where water forceson the parts of the structure below the BFE can be a significantportion of total lateral loads.

In a mid-rise structure greater than about four stories,wind is again a controlling factor in the design of the structuralframe, but water may play a significant role in the design of thelower walls of the building. In structures of three or fourstories, the effects of breaking or broken waves will be a majorconsideration, in addition to the requirements imposed by highwinds.

5.2 FOUNDATIONS

Foundation systems for mid- and high-rise structures aretypically pile foundations that are embedded deeply belowexisting ground elevations to provide a safety margin againstscour, as well as the required greater pile carrying capacity.Large load capacity is necessary because of the much highergravity loads, as well as the large lateral loads on high- or mid-rise structures.

High-rise buildings produce column loads far greaterthan those of even the most sophisticated low-rise buildings.Therefore, support must be provided by high-capacity, deeplyembedded foundations, usually piles. A 12-story residentialbuilding commonly has column loads of 250 to 300 tons at thefoundation; loads of such magnitude generally require pilegroups for adequate support. These pile groups are formedinto a single element by a pile cap of reinforced concrete uponwhich a building column is supported. Figure 5-1 shows atypical pile group and pile cap, and the connections of thereinforcement to the column and grade beam. A partiallycompleted pile cap for a three-pile group is shown in Figure 5-2.

Figure 5-1. Typical pile/pile cap/column/grade beam connection.

The most common types of piling used for the support ofmid- to high-rise structures are precast/prestressed concrete,cast-in-place concrete, steel, and timber. Precast concrete orsteel piles are usually driven with a large power (diesel orsteam) hammer to safe capacities of 50 to 100 tons. Timber isused at much lower capacities (maximum 25 tons per pile),primarily in smaller mid-rise structures.

In zones of reduced velocity and wave action, stripfoundations or combined footings and mat foundations areoccasionally used. These foundations must be buried to anadequate depth to protect against scour. If strip foundations a-re used, they should be oriented perpendicular to the shoreline(i.e., parallel to the expected flow of flood waters and waves).


5.3 SLABS AT GRADE

Floor slabs placed at ground level fall into two basiccategories for mid- to high-rise structures. Slabs that providefor parking areas or light traffic usage are typically supportedonly by the ground and are thin (4-inch) concrete slabs withminimal reinforcing in the form of welded wire mesh. The slabsare supported directly on the soil present at the site (usually acompacted sand), and in the event of a storm they areexpected to be undermined and lost. The other categoryincludes slabs that are essential to the safe functioning of thestructure, and must resist storm forces and erosion. These areslabs in storage areas, stairwells, mechanical rooms, etc.,whose necessary or useful functions are deemed desirable tohave as a permanent element of the building. In this case theyare

Figure 5-2. Pile to pile cap connection for high-rise foundations.(Note: Cap reinforcement not yet placed)

Figure 5-3. Skeleton framed building under construction.

Figure 5-4. Typical plan of high-rise building.


NOTE: FOR CLARITY, HORIZONTAL AND VERTICALREINFORCING IN THE SHEAR WALLIS NOT SHOWN. (SEE FIGURE 5-6)

Figure 5-5. Typical high-rise shear wall.

structurally designed, reinforced slabs, supported directly onpilings or indirectly on grade beams that are in turn supportedon pilings.

Grade beams such as the one shown in Figure 5-1areused not only to support structural ground floor slabs and wallsbut also to tie together individual piles or two-pile groups,which would otherwise be structurally unstable in at least onedirection. They are also used to increase lateral resistance of apile foundation system. In addition, grade beams (sometimescalled "strap beams") may be used to tie together columns thatform a part of a moment-resisting wind frame.

5.4 SUPERSTRUCTURE

The superstructure in most high-rise and some mid-risebuildings is generally of the type of construction known as askeleton frame. This framework of columns, beams, and slabsforms the skeleton of the building, which is then infilled withwalls and partitions. The building under construction in Figure5-3 has a skeleton frame. The most common framing materialfor high-rise construction in coastal areas is reinforcedmonolithic or poured-in-place concrete. Structural steel framedbuildings are occasionally used.

Figures 5-4 through 5-7 illustrate the key features ofhigh-rise construction. A typical skeleton high-rise is shown inplan in Figure 5-4. This building might be constructed asfollows:

Precast concrete piles are formed into pile caps, asshown in Figure 5-5. These pile caps support reinforcedconcrete columns, which in turn support a two-wayreinforced concrete slab (flat plate as shown in Figure 5-7). Shear walls would be placed at strategic locationswithin the building, generally


replacing two or more columns. Figure 5-6 shows theheavy reinforcement required for shear walls. The stairand elevator cores might be framed with beams andcolumns designed to carry both gravity and lateral loads.

High-rise buildings of more than seven stories generallyincorporate shear walls to provide for the transfer to thefoundation system of the lateral forces resulting from wind andwater loads. The shear walls are generally reinforcedconcrete walls 8, 10, or 12 inches in thickness, and arepositioned in the building such that wind loads are equallydivided among the walls. Wind loads are transferred to theshear walls by means of the floor diaphragm systems, whichact as deep beams. The shear walls then act as cantileverbeams fixed at their base to carry loads down to thefoundations. These shear walls are subjected to a variableshear that is greatest at the base, a

Figure 5-6. Shear wall reinforcement.

Figure 5-7. Typical high-rise floor slab section.

bending moment that causes tension at the loaded edge andcompression at the far edge, and an axial compression due toordinary gravity loading of the building.

In addition to shear walls, reinforced beam and columnframes may take a portion of the wind load so that the shearwalls do not have to do all of the work. Indeed, the floorsthemselves and their supporting columns interact with theshear walls to provide resistance to the lateral forces. Thisinteraction is the basis for modern efficient high-rise design.For mid-rise buildings that do not utilize bearing walls, thelateral forces are frequently taken by a combination of the slabsand columns, and/or the beam and column moment-resistingframes.

Bearing wall construction is very common for low- tomid-rise structures, although among the taller mid-rise


Figure 5-8. Typical plan of low- to mid-rise structure.

structures there are probably as many skeleton framedbuildings as bearing wall buildings. Bearing walls can be avery efficient means of construction in coastal regions. Bearingwalls provide not only for transferring gravity loads to thefoundation but also for very efficient lateral-force-resistingelements to transfer wind and/or water loads to thefoundations.

A typical low- to mid-rise bearing wall building is shownin plan in Figure 5-8. The bearing walls are aligned in thedirection of the primary water forces, although the building isdesigned for wind from any direction and water

forces over a range of angles to the shoreline. A sectionthrough the structure is shown on Figure 5-9, and illustratesthe reinforcement and connections between the foundations,bearing walls, and first elevated floor. A system of bearingwalls typically consists of reinforced masonry or pouredconcrete; the building illustrated in Figure 5-9 is reinforcedmasonry.

Figure 5-9. Typical section through low- to mid-rise bearing wall building.


Figure 5-10. Mid-rise residential structure with bearing walls.

Figure 5-10 shows a typical mid-rise condominium orapartment structure with grade level parking. Note that in thisexample the habitable floors are constructed using bearingwalls, while the elevated platform is supported on reinforcedconcrete columns and beams. Figure 5-lI shows a tallerstructure under construction that utilizes bearing walls; in thiscase the walls are poured concrete. Wood is a less frequentlyused structural material in mid-rise construction and isseldom found in structures over four stories high. Even heavytimber is generally inefficient for these larger structures.

5.5 ELEVATED FLOORS

Typical floor systems consist of poured-in-place, re-inforced concrete or composite precast concrete, in which

a portion of the floor is precast and a portion poured in place.

The reinforced concrete floors typically used inconjunction with bearing walls are one-way, in which theprimary reinforcing is in one direction and supported by thebearing walls. In skeleton construction, the floor slabs aretypically two-way reinforced (flat plate) slabs, in which there areno supports other than the columns and occasionally spandrel(perimeter) beams. Figure 5-12 shows a two-way slab in askeleton framed building. Note the masonry infill wall underconstruction on the upper floor.

The first elevated living floor in some mid-rise buildingsmay consist of a series of beams supported by the foundationpiles. These beams (shown in Figure 5-9) are monolithic withthe reinforced concrete slab, providing a heavy diaphragmthrough which the lateral forces are

Figure 5-11. High-rise structure with poured concrete bearing wallsunder construction.


Figure 5-12. Two-way slab in skeleton framed building.

transmitted to the piles. This system ties all of the piles togetherthrough this first-level diaphragm. The bottom of such a floorsystem should be considered to be exposed to weather, whichwould require greater concrete cover in accordance with theAmerican Concrete Institute (ACI) Code. It is also essential tosecurely connect the beams to the foundation piles.

5.6 EXTERIOR WALL SYSTEMS

The exterior wall systems used on the larger structures may bemasonry or metal stud with a finish of either

Figure 5-13. Elevated first floor on high-rise structure, partially enclosed bylattice.

stucco or composite material, of which there are several brandson today's market. These walls must be designed to resist thelateral forces imposed by hurricane winds. Most of thegoverning codes provide adequate requirements for theanchoring of masonry walls.

In utilizing metal studs, normal design criteria usingcode-specified loads will provide an adequate design;however, care must be taken in selecting proper techniques forfastening metal studs to a structural frame. Too often selectionof the fastening is left to the installer, and this can lead to poorlydesigned walls that will fail under hurricane or severe windloads.


Figure 5-14. Coastal construction with setback requirements.

More test data are required on the use of some of thefastening methods for exterior walls, such as powder-activateddrive pins, into various substrates. The effect of the length ofthe pin, its diameter, the power of the shot, etc., all affect thecapacity of the fastener. It is necessary, in the absence ofadequate test data, that manufacturers' recommendedstandards and a safety factor of 10 be applied to all powder-activated fasteners into concrete. The use of expansion bolts orother such devices also must be looked at carefully by thedesigner, not left up to the installer. Here again, adequatesafety factors, as recommended by the manufacturer (typically4), should be followed closely.

For exterior walls below the first living floor, thebreakaway wall design described elsewhere in this manualshould be followed, as illustrated by lattice enclosures inFigure 5-13. Exceptions include walls enclosing elevators,stairwells, and other essential areas, which should bedesigned to resist the anticipated lateral loads.

Interior walls are frequently stud partitions, metal orwood, although metal is used almost exclusively in mid- andhigh-rise structures. These partitions should be installedaccording to governing codes.

5.7 RECOMMENDATIONS

It is essential when designing a mid-rise or high-risestructure, particularly in a coastal area, that an experienceddesign professional be in charge of the design of such abuilding. Particularly for high-rise buildings, the design teamoften includes a geotechnical engineer and a coastal engineer.In addition to structural aspects discussed above,consideration must be given to subsurface conditions, erosionpotential, and other site-specific conditions affecting design.There also should be a requirement that a capable individualbe responsible for observing the construction of the building.

It is also important, as with smaller structures, thatsetback and dune protection provisions of local codes beobserved, as illustrated in Figure 5-13. Although in compliancewith minimum setback requirements, mid- and high-risestructures such as those shown in Figure 5-14 are vulnerableto major storms.

Design Procedures and Examples 6-1

Chapter 6

DESIGN PROCEDURESAND EXAMPLES

This chapter presents three design examples that detailthe step-by-step procedures for using the data and designtables in the appendices of this manual. The residentialstructure chosen for these examples is a one-story house 24feet wide and 40 feet long, with a wood pile foundation system.The general site layout and tentative house plans are shown inFigures 6-1 through 6-5.

The initial example is a one-story residential structure forwhich a foundation system is designed to be substantialenough not to require bracing. The second example is thesame house with a lighter foundation system, which requiresbracing. The third example considers the effects on thefoundation system of a breakaway wall installed below theBFE.

Procedures follow those outlined on the designworksheets presented in Appendix C, and follow the designrecommendations discussed in Chapter 4. Sampleworksheets illustrating these design examples appear with thedescriptions of the design procedures.

6.1 EXAMPLE 1--ELEVATION ON WOOD PILINGS

The owner or builder must determine the governingzoning and building code requirements, property lineclearances, easements, and site restrictions. The next step is toobtain the best available information on the severity of the floodhazard, specifically the design wind speed and the Base FloodElevation for the building site. In this example, the design windspeed is 110 mph and the BFE requires a clearance abovegrade of 7 feet (that is, the BFE

Figure 6-1. Site Plan


Figure 6-2. View from beach.

Figure 6-3. Main level plan.


minus the site elevation equals 7). Soil conditions should beinvestigated to determine proper pile lengths. Local buildingofficials are usually aware of general site and soil conditions;soil borings will provide the most reliable information. For thisdesign example the soil is assumed to be medium dense sand,and piles will be driven rather than jetted into place. (If pileswere to be jetted, loose sand conditions should be used in thecalculations.)

Entering all the data mentioned above on the PileDesign Worksheet (Figure 6-6) enables step-by-step use of theinformation in Appendix A. From Figure A-1, the possiblecombinations of numbers of piles in each direction aredetermined. In the 24-foot width, parallel to the beach, eitherthree piles at 12-foot spacing or four piles at 8-foot spacing canbe used, so this is entered onto the worksheet. The designtables are based upon equal spacing of piles, with 8-footspacing the minimum and 12 feet the maximum spacing. Forthe length of 40 feet, either five piles at 10-foot spacing or sixpiles at 8-foot spacing may be considered, and this is enteredonto the form. The total number of piles could thus be 15, 18,20, or 24. The reason for considering several pilearrangements is that the pile embedment and bracingrequirements are reduced when more piles are used. A finaldecision is best made after looking at several pilearrangements.

From Table A-1, the downward load per pile can bedetermined for a one-story house for the various numbers ofpiles to be considered. For example, for the configurationthree piles wide by six piles long, 18 piles total, the downwardforce on each pile is 5,598 pounds. The values for the variouspile arrangements are entered on the checklist.

Figure 6-4. Framing plan.


Figure 6-5. Ground level plan.

The pile embedment depth is next determined usingTable A-3. The data are presented for three types of piles:square 10-by-10 or 8-by-8-inch piles, or round piles with a tipdiameter of 8 inches. Interpolating in Table A-3 shows that forthe 18-pile group and 5,598-pound downward load, therequired pile penetration is 10.9 feet for an 8-by-8, 10.0 feet fora 10-by-10, and 12.8 feet for the round pile. Since this is abeachfront house, 8-by-8 piles should not be used, and only10-by-10 or round piles are appropriate. (The 8-by-8 data willbe carried forward, however, to demonstrate use of the tables.)Remember that, to accommodate scour, the pile tip must be atleast at -5 msl if the BFE (including wave height) is less than+10 msl, and the tip must be at least down to -10 msl if the BFEis +10 msl or higher. Note that recommendations in thismanual should be considered minimum requirements;deeper embedment is most beneficial.

The horizontal wind load per pile is obtained from TableA-2. For the 18-pile case the load per pile is 915 pounds.Again, the values for the various pile arrangements are enteredon the design worksheet form.

Next, one must check that the pile is capable of resistinghorizontal forces without bracing. A grade beam between allpiles is required. This may be wood or reinforced concrete,securely connected to the piles. Table A-4 presents data onmaximum unbraced height of piles above grade for the designwind speed considered (with associated water and debrisforces), so that allowable shear and bending stress in the pileis not exceeded. For example, to resist a horizontal wind forceof 915 pounds, the 8-by-8 pile can extend 6.0 feet above gradewithout bracing, the 10-by-10 about 8.6 feet, and the round pileabout 8.0 feet. Since the clear elevation of the bottom of floorbeams is 7 feet above grade, the pile combinations requiringbracing are all four of those using 8-by-8 square piles.


FIGURE 6-6

DESIGN EXAMPLE 1PILE DESIGN WORKSHEET

1 of 4

General Building Information

Width 24 feet

Length 40 feet

Number of Stories 1

Type of Soil MED DENSE SAND

Clearance Above Grade 7 feet

Design Wind Speed 110 miles per hour

Number of Piles Required (Figure A-1)

Along Width 3 or 4

Along Length 5 or 6

Combination (Width/Length) 3/5 or 3/6 or 4/5 or 4/6

Total Number (Width x Length) 15 or 18 or 20 or 24

Downward Load Per Pile (Table A-1) 6717 or 5598 or 5038 or 4198 pounds

Pile Embedment Depth (Table A-3)(No enclosure below BFE)

8x8 Square Pile 12.4 or 10.9 or 10.1 or 10.0 feet


8-inch Tip Round Pile 14.6 or 12.8 or 11.8 or 10.4 feet

Horizontal Wind Load Per Pile (Table A-2) 1098 or 915 or 823 or 686 pounds


FIGURE 6-6 (continued)

DESIGN EXAMPLE 1PILE DESIGN WORKSHEET (CONTINUED)

2 of 4

Maximum Unbraced Height of Pile (Table A-4)(No enclosure below BFE)




Is Bracing Required? (Does clearance above grade exceed maximum unbraced pile height?)(No enclosure below BFE)

8x8 Square Pile YES YES YES YES

10x10 Square Pile NO NO NO NO

8-inch Tip Round Pile NO NO NO NO

Information on Enclosure Below BFE NO ENCLOSURE

Width x Length __x__ or __x__ or __x__ or __x__ feet

Piles/Spacing Along Width __/__ or __/__ or __/__ or __/__

Piles/Spacing Along Length __/__ or __/__ or __/__ or __/__

No. of Piles in Enclosure ____ ____ ____ ____

No. of Piles Carrying Load ____ ____ ____ ____

Regulatory Breakaway Wall 10 to 20 psfPressure

Wall Height ____ feet




3 of 4

Load Resistance of Breakaway Walls NO BREAKAWAY WALLS

Selected Fastener Size

No. Fasteners per Loaded Panel ____ or ____ or ____ or ____

(Table A-11)

Ultimate Capacity per Fastener ____ pounds

(Table A-10)

Panel Ultimate Capacity ____ or ____ or ____ or ____ pounds

(No. fasteners x ultimate capacity each)

Total Breakaway Wall Capacity ____ or ____ or ____ or ____ pounds (Panel Ultimate Capacity ÷ No. Loaded Panels)

Horizontal Load per Pile at Breakaway N/A ____ or ____ or ____ or ____ pounds Wall Collapse (Total Wall Capacity ÷ No. of Piles Carrying Load)

Horizontal Load on Top Fasteners N/A ____ or ____ or ____ or ____ pounds (Horizontal Load ÷ 2)

Combined Horizontal Load per Pile N/A ____ or ____ or ____ or ____ pounds (Wind + Top Fastener Loads)

Maximum Unbraced Height of Pile (Table A - 4.1) N/A (Enclosure below BFE)

8x8 Square Pile ____ or ____ or ____ or ____ feet


8-inch Tip Round Pile ____ or ____ or ____ or ____ feet




4 of 4

Is Bracing Required? (Does clearance above grade exceed maximum unbraced pile height?) NO BRACING (Enclosure Below BFE)

8x8 Square Pile ____ ____ ____ ____

10x10 Square Pile ____ ____ ____ ____

8-inch Tip Round Pile ____ ____ ____ ____

Summary Information on Piles to be Used for BuildingNumber of Piles Selected

Along Width 3

Along Length 6

Total Number (Width x Length) 18

Size of Pile 10x10

Pile Embedment Depth 10.0 feet

Is Bracing Required? NO (if yes, see 'Bracing Design Worksheet')


FIGURE 6-7

DESIGN EXAMPLE 1CONNECTION DESIGN WORKSHEET

1 of 2

General House Information

Width 24 feet

Length 40 feet

Number of Stories 1


Connections Between Floors Uplift Loads per Foot of Wall (Table A-5)

Roof Connection 322 pounds per foot

Second Floor Connection N/A pounds per foot

First Floor Connection 300 pounds per foot

Connectors Selected Based on Manufacturers' Data (see Chapter 4.3.5)

Type TECO ANCH ORS

Spacing 16 inches



DESIGN EXAMPLE 1CONNECTION DESIGN WORKSHEET (CONTINUED)

2 of 2

Floor Beam Connection

Number of Piles Required (Figure A-1) 3/5 or 3/6 or 4/5 or 4/6

Combination (Width/Length)

Downward Load per Pile (Table A-1)

100% of Load 6717 or 5598 or 5038 or 4198 pounds

50% of Load 3359 or 2799 or 2519 or 2099 pounds

Uplift Load per Pile (Table A-6) 3039 or 2591 or 2280 or 1943 pounds

Capacity per Bolt of Selected Floor Beam Connection (Table A-7) 1450 pounds

Type of Connection STRAP

Beam

Bolt Diameter 3/4 inches

Number of Bolts 2

Pile

Bolt Diameter 3/4 inches

Number of Bolts 1


At this point in the design, for this house withoutenclosures below the BFE, it is possible to select the pilearrangement that is preferred and economical. However, theconnections of the floor beams to the piles may influence thedecision. Therefore, let us determine the forces on some of theconnections that must be designed (see Connection DesignWorksheet, Figure 6-7).

Table A-5 presents the net uplift forces that must beresisted by connections at the various levels of a house: roof,second floor, and first floor. The data are presented as upliftload per foot so that one can decide on the type of connector.For our example the upward force at the roof line is 322pounds per foot along two walls, so the roof members must beconnected to the top of the stud wall to resist this load.Similarly, the upward force at the first floor is 300 pounds perfoot; wall anchor straps and joist anchors to floor beams arerequired to resist this force.

One must also provide a positive connection of floorbeam to pile to resist upward wind loads. Table A-6 gives theuplift force per pile that must be provided for in the design ofthe connection. For the 18 piles of the design example, theuplift force is 2,591 pounds; suitable bolts are needed. TableA-7 gives the capacities of various connections of floor beamsto piles. Figures in Chapter 4 illustrate the various connectionslisted in Table A-7. A reasonable connection to select for theloads to be resisted in the 18-pile case would be a strap withtwo bolts of 3/4 inch at the beam and one 3/4-inch bolt at thepile. This would not be adequate for the 15-pile case, and thusmay influence the selection of an appropriate pile system forthe house.

One can finalize the pile selection, based upon theseveral arrangements that will work, by choosing that which isconsidered the most suitable in terms of cost and aesthetics.For example, a reasonable selection would be

18 of the 10-by-10 piles, with three piles widthwise and sixlengthwise. The piles would be embedded to at least 10.0 feetbelow grade, with an overall pile length of 17 feet.

6.2 EXAMPLE 2--BRACING REQUIRED

This example will consider the same house and pileconfigurations evaluated in Example 1. However, in this casethe BFE will be assumed higher and clearance above gradewill be assumed as 11 feet, in order to illustrate use of theBracing Design Worksheet in Appendix C.

The Pile Design Worksheet is completed as in Example1, except this time the clearance above grade is 11 feet (Figure6-8). Pile configurations, downward load per pile, and pileembedment depth are the same as Example 1. Horizontalwind loads per pile are increased by a factor of 1.07 for theincreased building height above grade, as noted in Table A-2.Maximum unbraced height of piles resisting the input wind loadand associated water load is again obtained from Table A-4. Inthis example, clearance above grade exceeds maximumunbraced height, and bracing is required for all pile systemsbeing considered.

Proceeding to the Bracing Design Worksheet (Figure 6-9), house information and maximum unbraced pile heights arerepeated for ease of reference. If clearance above grade (pileheight) exceeds maximum unbraced height by 4 feet or less,knee braces can be used. For purposes of this example, it willbe assumed that 8-by-8 square is the only readily availablepile type in the area. (In reality, as noted in Chapter 4, largerpiles are generally recommended for the first row of housesfrom shore.) Since pile height exceeds maximum unbracedheight for all configurations of the 8-by-8 piles, bracing will berequired.


FIGURE 6-8


1 of 4


Width 24 feet

Length 40 feet

Number of Stories 1





Along Width 3 or 4

Along Length 5 or 6












2 of 4








8-inch Tip Round Pile YES YES YES YES

Information on Enclosure Below BFE NO ENCLOSURE

Width x Length __x__ or __x__ or __x__ or __x__ feet

Piles/Spacing Along Width __/__ or __/__ or __/__ or __/__

Piles/Spacing Along Length __/__ or __/__ or __/__ or __/__

No. of Piles in Enclosure ____ ____ ____ ____

No. of Piles Carrying Load ____ ____ ____ ____


Wall Height ____ feet




3 of 4

Load Resistance of Breakaway Walls NO BREAKAWAY WALLS

Selected Fastener Size

No. Fasteners per Loaded Panel ____ or ____ or ____ or ____

(Table A-11)

Ultimate Capacity per Fastener ____ pounds

(Table A-10)

Panel Ultimate Capacity ____ or ____ or ____ or ____ pounds


Total Breakaway Wall Capacity ____ or ____ or ____ or ____ pounds (Panel Ultimate Capacity ÷ No. Loaded Panels)

Horizontal Load per Pile at Breakaway N/A ____ or ____ or ____ or ____ pounds Wall Collapse (Total Wall Capacity ÷ No. of Piles Carrying Load)

Horizontal Load on Top Fasteners N/A ____ or ____ or ____ or ____ pounds

(Horizontal Load ÷ 2)

Combined Horizontal Load per Pile N/A ____ or ____ or ____ or ____ pounds (Wind + Top Fastener Loads)

Maximum Unbraced Height of Pile (Table A - 4.1) N/A (Enclosure below BFE)



8-inch Tip Round Pile ____ or ____ or ____ or ____ feet




4 of 4

Is Bracing Required? (Does clearance above grade exceed maximum unbraced pile height?) NO BRACING (Enclosure Below BFE)

8x8 Square Pile ____ ____ ____ ____

10x10 Square Pile ____ ____ ____ ____

8-inch Tip Round Pile ____ ____ ____ ____


Along Width 3

Along Length 6


Size of Pile 8x8


Is Bracing Required? YES (if yes, see 'Bracing Design Worksheet')


FIGURE 6-9

DESIGN EXAMPLE 2BRACING DESIGN WORKSHEET

1 of 3


Width 24 feet

Length 40 feet

Number of Stories 1





Maximum Unbraced Height of Pile (Table A-4)




Can Knee Braces Be Used? (Is clearance above grade minus maximum unbraced height 4 feet or less?)

8x8 Square Pile NO or NO or NO or NO

10x10 Square Pile YES or YES or YES or YES

8-inch Tip Round Pile YES or YES or YES or YES

If Knee Bracing Cannot Be Used, Continue on for Truss Bracing



DESIGN EXAMPLE 2BRACING DESIGN WORKSHEET (CONTINUED)

2 of 3

Horizontal Water Loads per Pile (Table B-1)

8x8 Square Pile 2738 pounds

10x 10 Square Pile ____ pounds

8-inch Tip Round Pile ____ pounds

Horizontal Wind Loads per Pile (Table A-2) 1175 or 979 or 881 or 734 pounds

Combined Horizontal Loads per Pile (Wind + Water)

8x8 Square Pile 3913 or 3717 or 3619 or 3472 pounds

10x10 Square Pile ____ or ____ or ____ or ____ pounds

8-inch Tip Round Pile ____ or ____ or ____ or ____ pounds

Truss Width = B = Pile Spacing Along Length 10 or 8 or 10 or 8 feet

A/B Ratio for Diagonal Members (Figure B-I) 1.1 or 1.4 or 1.1 or 1.4 feet

Loads on Transverse Members (Table B-2)

Struts




Diagonals






DESIGN EXAMPLE 2BRACING DESIGN WORKSHEET (CONTINUED)

3 of 3

Information on Bracing to be Used for Selected Pile Combination

Strut Size (Table B-5) 4x8

Diagonals (Tables B-3 and B-4)

Single or Double D oubl e

Size 2x8

"A" Bolt (yes/no) YES


Horizontal water loads per pile are obtained from TableB-1 and combined with horizontal water loads from Table A-2.This is the input load for Table B-2. For the A/B ratio for thistable, A is the pile height and B is the pile spacing, as indicatedby Figure B-1. A single level of truss bracing can be used forpile heights up to about 12 feet, above which a double levelshould be used. Loads on the struts and diagonals are theninterpolated from Table B-2 for the given combined loads andA/B ratios.

Based on these loads in the truss members, the size ofmembers can be selected from Tables B-3, B-4, and B-5. Forthis example, the strut should be at least 4-by-8 or equivalent(Table B-5). For the 18-pile case, the diagonal load of 9,592pounds exceeds the capacity of a single 3-by-8 with one "A"bolt (9,000-pound capacity, Table B-4). The diagonal loadcould be carried by a double 2-by-8 with one "A" bolt;alternatively, the designer could consider one of the other pileconfigurations, which do not require doubling the beams. Tocomplete the Pile Design Worksheet, if the 18-pile combinationis chosen, it is recorded as the selected combination of 8-by-8piles, with pile embedment depth of at least 10.9 feet.Connection design is then checked as in Example 1.

6.3 EXAMPLE 3--BREAKAWAY WALLS

In this example, the same one-story house fromExample 1 is to have part of the space below the BFE enclosedby breakaway walls. These walls are to be designed to breakaway before the storm forces applied to the walls become largeenough to damage the house foundation system.

The Pile Design Worksheet (Figure 6-10) is filled outsimilarly to Example 1, up through the determination of whetherabove-grade bracing is required without

breakaway walls. For the pile combinations being consideredfor the house, several breakaway enclosure areas can beconsidered as illustrated on the worksheet. The number ofpiles attached to or enclosed by the walls is then recorded.The number of piles carrying the load of the breakaway walls isconsidered to be those piles attached to or within 8 feet of thewall.

Regulatory breakaway wall pressure is the range ofworking load within which breakaway walls must be designed,presently specified by NFIP as between 10 and 20 psf, unlessthe walls and the effects of the walls on the overall structure aredesigned by a registered engineer or architect. Wall height isthe height of each panel (7 feet in this example).

Load resistance of each breakaway wall panel isconsidered to be the total capacity of the fasteners, which areinstalled along the top and bottom of the panel. Table A-11gives the range of total number of fasteners per panel that willresult in a wall with a design safe loading resistance between10 and 20 psf; these numbers are developed for severalcommon wall sizes directly from the fastener capacities inTable A-10.

If 10d nails are considered for this example, the numberrequired per panel is selected from Table A-11 and noted onthe worksheet. (Choosing the minimum number of nailsminimizes the load applied to the piles before breakaway wallcollapse.) The pile spacing is that along the wall directlyloaded by the storm forces.

The total load resisted by the breakaway wall beforecollapse equals the ultimate capacity of all the fasteners on allthe directly loaded panels. Ultimate capacity per fastener isgiven in Table A-10. This value times the number of fastenersper panel times the number of loaded panels gives totalbreakaway wall capacity. Dividing by


FIGURE 6-10


1 of 4


Width 24 feet

Length 40 feet

Number of Stories 1




Number of Piles Required (Figure A-I)

Along Width 3 or 4

Along Length 5 or 6












2 of 4









Information on Enclosure Below BFE

Width x Length 24 x 20 or 12 x 32 or 16 x 30 or 16 x 32 feet

Piles/Spacing Along Width 3 / 12’ or 2 / 12’ or 3 / 8’ or 3 / 8’

Piles/Spacing Along Length 3 / 10’ or 5 / 8’ or 4 / 10’ or 5 / 8’

No. of Piles in Enclosure 9 10 12 15

No. of Piles Carrying Load 7 10 12 15


Wall Height 7.0 feet




3 of 4

Load Resistance of Breakaway Walls

Selected Fastener Size 10d

No. Fasteners per Loaded Panel 10 or 10 or 6 or 6

(Table A-11)

Ultimate Capacity per Fastener 425 pounds

(Table A-10)

Panel Ultimate Capacity 4250 or 4250 or 2550 or 2550 pounds


Total Breakaway Wall Capacity 8500 or 4250 or 5100 or 5100 pounds (Panel Ultimate Capacity ÷ No. Loaded Panels)

Horizontal Load per Pile at Breakaway 1214 or 425 or 425 or 340 pounds Wall Collapse (Total Wall Capacity ÷ No. of Piles Carrying Load)

Horizontal Load on Top Fasteners 607 or 213 or 213 or 170 pounds (Horizontal Load ÷ 2)

Combined Horizontal Load per Pile 1705 or 1128 or 1036 or 856 pounds (Wind + Top Fastener Loads)

Maximum Unbraced Height of Pile (Table A - 4.1) (Enclosure below BFE)







4 of 4

Is Bracing Required? (Does clearance above grade exceed maximum unbraced pile height?) (Enclosure Below BFE)





Along Width 3

Along Length 6


Size of Pile 10x10


Is Bracing Required? NO (if yes, see 'Bracing Design Worksheet')


the number of piles carrying the load (previously determined)gives the maximum load per pile at the moment of collapse.

In order to evaluate whether the foundation system canwithstand the forces applied to the enclosure walls before theybreak away, the combined horizontal loads which producemoment about the pile base must be considered. Thiscombined load consists of the half of the breakaway wall loadapplied at the top of the pile (the other half is applied at thebottom, producing no moment), plus the wind load on thesuperstructure. For this combined load, Table A-4.l gives themaximum height a pile can extend above grade withoutbracing. If house clearance above grade exceeds this height,bracing is required.

In this example, none of the configurations of pile typesand enclosure areas considered are found to require bracingagainst the breakaway wall loads. Therefore a foundationsystem of 10-by-10 piles such as that selected in Example 1will withstand the loads transmitted to the piles beforebreakaway wall collapse. As in Example 1, connectionsshould be checked and may influence the foundationconfiguration selected.

For all breakaway walls, whether or not bracing isindicated by these calculations, knee braces should beinstalled on the front row piles attached to the wall directlyloaded by the storm forces, to assist in load distribution. Inaddition, if floor beams do not run in the direction of theexpected water loading, compression struts should be installedin the direction of loading between the tops of all pilesassumed to carry the water load.

Design Tables A-1

Appendix A

DESIGN TABLES

In this appendix are presented tables for use indesigning residential structures in coastal high hazard areas.Their use is explained and demonstrated in Chapter 6, andmany of the concepts on which they are based are discussedin Chapter 4. The computer programs that generate the tablesare presented in Appendix E.

The data in these tables represent a range of typicalhouse dimensions, 20 to 40 feet in width (parallel to beach) orlength (perpendicular to beach), and one or two stories inheight. Each story is assumed to be 9 feet high. The roof isassumed to be sloped 3 horizontal to 1 vertical, with ridgeparallel to the wind, and with 2-foot eaves all around. Unlessprovided for otherwise, the clearance from ground to loweststructural member of the house frame is assumed to be 8 feet.Input design wind speeds are intended to be those specified bythe local building code or those given by ANSI for a 100 yearmean recurrence interval.

FIGURE A-1 NUMBER OF PILES REQUIRED

This figure permits one to read off thenumber of piles that will be required for eachdimension of a house. It is assumed that piles areequally spaced, with a minimum spacing of 8 feetand a maximum spacing of 12 feet. For example,if the length of a side is 32 feet, one can use fourpiles at about 10-foot-8-inch spacing or five pilesat 8-foot spacing.

Figure A-1. Number of piles required.

A-2 Coastal Construction Manual

TABLE A-1 DOWNWARD LOADS PER PILE

This table presents the design loads fromthe house that each pile must support andleads to the selection of pile embedmentdepth.

TABLE A-2 HORIZONTAL WIND LOADS PER PILE

This table presents the design loads fromwind that each pile must withstand and leadsto a determination of the type of bracing thepiles may need.

ABLE A-3 MINIMUM EMBEDMENT DEPTH OF PILES

This table presents the minimum depthsto which piles must be placed in order tosupport the indicated loads.

TABLE A-4 MAXIMUM UNBRACED HEIGHT OF PILES

This table presents the maximum heightabove grade a pile can be used withouthorizontal bracing being necessary.

TABLE A-4.1 MAXIMUM UNBRACED HEIGHT OF PILESSUPPORTING BREAKAWAY WALLS.

TABLE A-5 UPLIFT LOADS PER FOOT OF WALL

This table presents the design wind loadsapplied to the connectors between floors.

TABLE A-6 UPLIFT LOADS PER PILE

This table presents the design loads dueto wind that the floor beam to pile connectionmust resist in order to keep the house on thepiles.

TABLE A-7 CAPACITY PER BOLT OF FLOOR BEAMCONNECTIONS

This table presents design loads forvarious sizes of bolts and various types of floorbeam connections.

TABLE A-8 CONCRETE MASONRY UNIT PIERS

This table presents the reinforcing steelrequirements for these piers. Since wind froma hurricane can occur in most directions,square piers with the same reinforcements inall four faces should be used. Matchingvertical steel dowels should be anchored inthe footing or grade beam.

TABLE A-9 CONCRETE PIERS

This table presents the reinforcing steelrequirements for these piers. Since wind canoccur in most directions from a hurricane,square piers with the same reinforcements inall four faces should be used. Matchingvertical steel dowels should be anchored inthe footing or grade beam.

Design Tables A-3

FIGURE A-2 CONCRETE PIER CROSS SECTION

This graphic illustrates and providessupplementary information to Table A-9.

FIGURE A-3 GRADE BEAMS AND SLABS

Nominal reinforcement is required ingrade beams and slabs, as shown in thisdiagram. Grade beams should be firmlyanchored to piers or piles, whether concrete orwood.

TABLE A-10 FASTENER CAPACITIES IN SHEAR

Working and ultimate capacities (inpounds) are provided for No. 6, S-I2 screwsand for nail sizes 8d through 16d, both lateraland toe nailed. Capacity for the common sizedowel pin used in masonry walls is alsoprovided.

TABLE A-11 FASTENER SCHEDULE FORBREAKAWAY WALLS

The ranges of total numbers of fastenersneeded to achieve a design safe loadingresistance between 10 and 20 pounds persquare foot are provided for combinations ofwall height and pile spacing. The tables covernail sizes from 8d to 16d (for wood stud walls)and No. 6, S-12 screws (for metal stud walls).


TABLE A-1

DOWNWARD LOADS PER PILE (POUNDS)

FOR ONE-STORY HOUSES

WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40LENGTH NUMBER(FEET) OF PILES 3 3 4 4 4 4 5 5 5 6

20 3 4971 5872 4404 5079 5754 6430 4603 5144 5684 473624 3 5872 6936 5202 6001 6800 7598 5440 6078 6717 559824 4 4404 5202 3902 4501 5100 5699 4080 4559 5038 419828 4 5079 6001 4501 5192 5884 6575 4707 5260 5813 484432 4 5754 6800 5100 5884 6668 7452 5334 5961 6588 549036 4 6430 7598 5699 6575 7452 8328 5961 6662 7364 613632 5 4603 5440 4080 4707 5334 5961 4267 4769 5271 439236 5 5144 6078 4559 5260 5961 6662 4769 5330 5891 490940 5 5684 6717 5038 5813 6588 7364 5271 5891 6511 542640 6 4736 5598 4198 4844 5490 6136 4392 4909 5426 4521

FOR TWO-STORY HOUSES


20 3 6682 7925 5944 6876 7808 8740 6246 6992 7737 644824 3 7925 9400 7050 8157 9264 10370 7411 8296 9181 765124 4 5944 7050 5288 6118 6948 7778 5558 6222 6886 573828 4 6876 8157 6118 7079 8040 9001 6432 7200 7969 664132 4 7808 9264 6948 8040 9132 10224 7305 8179 9052 754436 4 8740 10370 7778 9001 10224 11447 8179 9157 10136 844632 5 6246 7411 5558 6432 7305 8179 5844 6543 7242 603536 5 6992 8296 6222 7200 8179 9157 6543 7326 8108 675740 5 7737 9181 6886 7969 9052 10136 7242 8108 8975 747940 6 6448 7651 5738 6641 7544 8446 6035 6757 7479 6232

NOTE: SEE APPENDIX INTRODUCTION FOR ASSUMED HOUSE DIMENSIONS.

Design Tables A-5

TABLE A-2

HORIZONTAL WIND LOADS PER PILE (POUNDS) IN 80 MPH WINDS



20 3 781 967 726 873 1028 1190 822 952 1088 90624 3 781 967 726 873 1028 1190 822 952 1088 90624 4 586 726 544 655 771 892 617 714 816 68028 4 586 726 544 655 771 892 617 714 816 68032 4 586 726 544 655 771 892 617 714 816 68036 4 586 726 544 655 771 892 617 714 816 68032 5 469 580 435 524 617 714 493 571 653 54436 5 469 580 435 524 617 714 493 571 653 54440 5 469 580 435 524 617 714 493 571 653 54440 6 391 484 363 436 514 595 411 476 544 453



20 3 1477 1804 1353 1606 1867 2136 1494 1709 1930 160824 3 1477 1804 1353 1606 1867 2136 1494 1709 1930 160824 4 1108 1353 1015 1205 1400 1602 1120 1282 1448 120628 4 1108 1353 1015 1205 1400 1602 1120 1282 1448 120632 4 1108 1353 1015 1205 1400 1602 1120 1282 1448 120636 4 1108 1353 1015 1205 1400 1602 1120 1282 1448 120632 5 886 1082 812 964 1120 1282 896 1025 1158 96536 5 886 1082 812 964 1120 1282 896 1025 1158 96540 5 886 1082 812 964 1120 1282 896 1025 1158 96540 6 739 902 677 803 934 1068 747 854 965 804

NOTES: 1. THESE VALUES APPLY FOR CLEARANCE ABOVE EXISTING GRADE OF 8 FEET OR LESS. FOR CLEARANCESGREATER THAN 8 FEET, LESS THAN OR EQUAL TO 14 FEET, MULTIPLY THESE VALUES BY 1.07. FORCLEARANCES GREATER THAN 14 FEET, LESS THAN OR EQUAL TO 22 FEET, MULTIPLY THESE VALUES BY 1.13.

2. SEE APPENDIX INTRODUCTION FOR ASSUMED HOUSE DIMENSIONS.


TABLE A-2 CONTINUED



WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40LENGTH NUMBER (FEET) OF PILES 3 3 4 4 4 4 5 5 5 6

20 3 989 1225 918 1105 1301 1506 1041 1205 1377 114724 3 989 1225 918 1105 1301 1506 1041 1205 1377 114724 4 742 918 689 829 975 1130 780 904 1033 86028 4 742 918 689 829 975 1130 780 904 1033 86032 4 742 918 689 829 975 1130 780 904 1033 86036 4 742 918 689 829 975 1130 780 904 1033 86032 5 593 735 551 663 780 904 624 723 826 68836 5 593 735 551 663 780 904 624 723 826 68840 5 593 735 551 663 780 904 624 723 826 68840 6 494 612 459 552 650 753 520 602 688 574



20 3 1870 2284 1713 2033 2363 2704 1891 2163 2443 203624 3 1870 2284 1713 2033 2363 2704 1891 2163 2443 203624 4 1402 1713 1285 1525 1773 2028 1418 1622 1832 152728 4 1402 1713 1285 1525 1773 2028 1418 1622 1832 152732 4 1402 1713 1285 1525 1773 2028 1418 1622 1832 152736 4 1402 1713 1285 1525 1773 2028 1418 1622 1832 152732 5 1122 1370 1028 1220 1418 1622 1134 1298 1466 122236 5 1122 1370 1028 1220 1418 1622 1134 1298 1466 122240 5 1122 1370 1028 1220 1418 1622 1134 1298 1466 122240 6 935 1142 856 1017 1182 1352 945 1081 1222 1018



Design Tables A-7

TABLE A-2 CONTINUED

HORIZONTAL WIND LOADS PER PILE (POUNDS) IN 100 MPH WINDS FOR

ONE-STORY HOUSES


20 3 1221 1512 1134 1364 1606 1859 1284 1487 1700 141624 3 1221 1512 1134 1364 1606 1859 1284 1487 1700 141624 4 915 1134 850 1023 1204 1394 963 1115 1275 106228 4 915 1134 850 1023 1204 1394 963 1115 1275 106232 4 915 1134 850 1023 1204 1394 963 1115 1275 106236 4 915 1134 850 1023 1204 1394 963 1115 1275 106232 5 732 907 680 818 963 1115 771 892 1020 85036 5 732 907 680 818 963 1115 771 892 1020 85040 5 732 907 680 818 963 1115 771 892 1020 85040 6 610 756 567 682 803 930 642 744 850 708



20 3 2308 2819 2114 2510 2917 3338 2334 2670 3016 251324 3 2308 2819 2114 2510 2917 3338 2334 2670 3016 251324 4 1731 2114 1586 1882 2188 2503 1750 2003 2262 188528 4 1731 2114 1586 1882 2188 2503 1750 2003 2262 188532 4 1731 2114 1586 1882 2188 2503 1750 2003 2262 188536 4 1731 2114 1586 1882 2188 2503 1750 2003 2262 188532 5 1385 1691 1269 1506 1750 2003 1400 1602 1810 150836 5 1385 1691 1269 1506 1750 2003 1400 1602 1810 150840 5 1385 1691 1269 1506 1750 2003 1400 1602 1810 150840 6 1154 1409 1057 1255 1459 1669 1167 1335 1508 1257




TABLE A-2 CONTINUED




20 3 1477 1829 1372 1650 1943 2250 1554 1800 2057 171424 3 1477 1829 1372 1650 1943 2250 1554 1800 2057 171424 4 1108 1372 1029 1238 1457 1687 1166 1350 1542 128528 4 1108 1372 1029 1238 1457 1687 1166 1350 1542 128532 4 1108 1372 1029 1238 1457 1687 1166 1350 1542 128536 4 1108 1372 1029 1238 1457 1687 1166 1350 1542 128532 5 886 1098 823 990 1166 1350 933 1080 1234 102836 5 886 1098 823 990 1166 1350 933 1080 1234 102840 5 886 1098 823 990 1166 1350 933 1080 1234 102840 6 739 915 686 825 971 1125 777 900 1028 857



20 3 2793 3411 2559 3037 3531 4039 2824 3231 3650 304124 3 2793 3411 2559 3037 3531 4039 2824 3231 3650 304124 4 2095 2559 1919 2278 2648 3029 2118 2423 2737 228128 4 2095 2559 1919 2278 2648 3029 2118 2423 2737 228132 4 2095 2559 1919 2278 2648 3029 2118 2423 2737 228136 4 2095 2559 1919 2278 2648 3029 2118 2423 2737 228132 5 1676 2047 1535 1822 2118 2423 1695 1939 2190 182536 5 1676 2047 1535 1822 2118 2423 1695 1939 2190 182540 5 1676 2047 1535 1822 2118 2423 1695 1939 2190 182540 6 1397 1706 1279 1519 1765 2019 1412 1616 1825 1521



Design Tables A-9

TABLE A-2 CONTINUED




20 3 1758 2177 1633 1964 2312 2677 1850 2142 2448 204024 3 1758 2177 1633 1964 2312 2677 1850 2142 2448 204024 4 1318 1633 1225 1473 1734 2008 1387 1606 1836 153028 4 1318 1633 1225 1473 1734 2008 1387 1606 1836 153032 4 1318 1633 1225 1473 1734 2008 1387 1606 1836 153036 4 1318 1633 1225 1473 1734 2008 1387 1606 1836 153032 5 1055 1306 980 1178 1387 1606 1110 1285 1469 122436 5 1055 1306 980 1178 1387 1606 1110 1285 1469 122440 5 1055 1306 980 1178 1387 1606 1110 1285 1469 122440 6 879 1089 816 982 1156 1339 925 1071 1224 1020



20 3 3324 4060 3045 3614 4201 4806 3361 3845 4343 361924 3 3324 4060 3045 3614 4201 4806 3361 3845 4343 361924 4 2493 3045 2284 2711 3151 3605 2521 2884 3257 271528 4 2493 3045 2284 2711 3151 3605 2521 2884 3257 271532 4 2493 3045 2284 2711 3151 3605 2521 2884 3257 271536 4 2493 3045 2284 2711 3151 3605 2521 2884 3257 271532 5 1994 2436 1827 2169 2521 2884 2017 2307 2606 217236 5 1994 2436 1827 2169 2521 2884 2017 2307 2606 217240 5 1994 2436 1827 2169 2521 2884 2017 2307 2606 217240 6 1662 2030 1522 1807 2101 2403 1681 1923 2172 1810

NOTES: 1. THESE VALUES APPLY FOR CLEARANCE ABOVE EXISTING GRADE OF 8 FEET OR LESS. FOR CLEARANCESGREATER THAN 8 FEET, LESS THAN OR EQUAL TO 14 FEET. MULTIPLY THESE VALUES BY 1.07. FORCLEARANCES GREATER THAN 14 FEET, LESS THAN OR EQUAL TO 22 FEET, MULTIPLY THESE VALUES BY 1.13.



TABLE A-2 CONTINUED




20 3 2063 2555 1916 2305 2714 3142 2171 2514 2873 239424 3 2063 2555 1916 2305 2714 3142 2171 2514 2873 239424 4 1547 1916 1437 1729 2035 2357 1628 1885 2155 179528 4 1547 1916 1437 1729 2035 2357 1628 1885 2155 179532 4 1547 1916 1437 1729 2035 2357 1628 1885 2155 179536 4 1547 1916 1437 1729 2035 2357 1628 1885 2155 179532 5 1238 1533 1150 1383 1628 1885 1303 1508 1724 143636 5 1238 1533 1150 1383 1628 1885 1303 1508 1724 143640 5 1238 1533 1150 1383 1628 1885 1303 1508 1724 143640 6 1032 1278 958 1153 1357 1571 1086 1257 1438 1197



20 3 3901 4765 3574 4242 4931 5641 3945 4513 5098 424824 3 3901 4765 3574 4242 4931 5641 3945 4513 5098 424824 4 2926 3574 2680 3182 3699 4231 2959 3385 3823 318628 4 2926 3574 2680 3182 3699 4231 2959 3385 3823 318632 4 2926 3574 2680 3182 3699 4231 2959 3385 3823 318636 4 2926 3574 2680 3182 3699 4231 2959 3385 3823 318632 5 2341 2859 2144 2545 2959 3385 2367 2708 3059 254936 5 2341 2859 2144 2545 2959 3385 2367 2708 3059 254940 5 2341 2859 2144 2545 2959 3385 2367 2708 3059 254940 6 1951 2382 1787 2121 2466 2821 1973 2257 2549 2124

NOTES: 1. THESE VALUES APPLY FOR CLEARANCE ABOVE EXISTING GRADE OF 8 FEET OR LESS. FOR CLEARANCESGREATER THAN 8 FEET, LESS THAN OR EQUAL TO 14 FEET. MULTIPLY THESE VALUES BY 1.07. FORCLEARANCES GREATER THAN 14 FEET, LESS THAN OR EQUAL TO 22 FEET, MULTIPLY THESE VALUES BY 1.13.


Design Tables A-11

TABLE A-2 CONTINUED




20 3 2393 2963 2223 2674 3147 3644 2518 2916 3332 277624 3 2393 2963 2223 2674 3147 3644 2518 2916 3332 277624 4 1795 2223 1667 2005 2361 2733 1888 2187 2499 208228 4 1795 2223 1667 2005 2361 2733 1888 2187 2499 208232 4 1795 2223 1667 2005 2361 2733 1888 2187 2499 208236 4 1795 2223 1667 2005 2361 2733 1888 2187 2499 208232 5 1436 1778 1334 1604 1888 2187 1511 1749 1999 166636 5 1436 1778 1334 1604 1888 2187 1511 1749 1999 166640 5 1436 1778 1334 1604 1888 2187 1511 1749 1999 166640 6 1196 1482 1111 1337 1574 1822 1259 1458 1666 1388



20 3 4525 5526 4145 4920 5719 6543 4575 5234 5912 492724 3 4525 5526 4145 4920 5719 6543 4575 5234 5912 492724 4 3393 4145 3108 3690 4289 4907 3431 3926 4434 369528 4 3393 4145 3108 3690 4289 4907 3431 3926 4434 369532 4 3393 4145 3108 3690 4289 4907 3431 3926 4434 369536 4 3393 4145 3108 3690 4289 4907 3431 3926 4434 369532 5 2715 3316 2487 2952 3431 3926 2745 3140 3547 295636 5 2715 3316 2487 2952 3431 3926 2745 3140 3547 295640 5 2715 3316 2487 2952 3431 3926 2745 3140 3547 295640 6 2262 2763 2072 2460 2860 3271 2288 2617 2956 2463

NOTES: 1. THESE VALUES APPLY FOR CLEARANCE ABOVE EXISTING GRADE OF 8 FEET OR LESS. FOR CLEARANCESGREATER THAN 8 FEET, LESS THAN OR EQUAL TO 14 FEET, MULTIPLY THESE VALUES BY 1.07. FORCLEARANCES GREATER THAN 14 FEET, LESS THAN OR EQUAL TO 22 FEET. MULTIPLY THESE VALUES BY 1.13.



TABLE A-3

MINIMUM EMBEDMENT DEPTH OF PILES (FEET)

VERTICAL MEDIUM DENSE SAND LOOSE SAND MEDIUM STIFF CLAY SOFT CLAY LOAD 8x8 10x10 8INCH 8X8 10x10 8INCH 8X8 10x10 8INCH 8X8 10X10 8INCH(POUNDS) PILES PILES TIP PILES PILES TIP PILES PILES TIP PILES PILES TIP

3000 10.0 10.0 10.0 13.4 10.0 15.5 10.0 10.0 10.0 10.0 10.0 10.03500 10.0 10.0 10.0 15.0 11.3 17.3 10.0 10.0 10.0 10.0 10.0 10.04000 10.0 10.0 10.0 16.5 12.5 18.9 10.0 10.0 10.0 10.5 10.0 10.04500 10.0 10.0 10.8 17.9 13.7 20.4 10.0 10.0 10.0 12.0 10.0 10.95000 10.0 10.0 11.7 19.3 14.8 21.8 10.0 10.0 10.0 13.5 10.1 12.15500 10.7 10.0 12.6 20.6 15.9 23.2 10.0 10.0 10.0 15.0 11.3 13.46000 11.4 10.0 13.4 21.9 17.0 24.5 10.0 10.0 10.0 16.5 12.5 14.66500 12.1 10.0 14.2 23.1 18.0 25.8 10.0 10.0 10.0 18.0 13.7 15.87000 12.8 10.0 15.0 24.3 19.0 27.0 10.2 10.0 10.0 19.5 14.9 16.97500 13.5 10.0 15.8 25.4 20.0 28.1 11.0 10.0 10.1 21.0 16.1 18.18000 14.2 10.5 16.5 26.6 21.0 29.2 11.8 10.0 10.8 22.5 17.3 19.28500 14.9 11.1 17.2 27.6 21.9 30.3 12.7 10.0 11.4 24.0 18.5 20.49000 15.5 11.6 17.9 28.7 22.8 31.3 13.5 10.1 12.1 25.5 19.7 21.59500 16.1 12.1 18.6 29.7 23.7 32.4 14.3 10.8 12.8 27.0 20.9 22.6

10000 16.8 12.6 19.3 30.7 24.5 33.3 15.2 11.5 13.5 28.5 22.1 23.710500 17.4 13.1 19.9 31.7 25.4 34.3 16.0 12.1 14.2 30.0 23.3 24.811000 18.0 13.6 20.5 32.7 26.2 35.2 16.8 12.8 14.8 31.5 24.5 25.911500 18.5 14.0 21.1 33.6 27.0 36.1 17.7 13.5 15.5 33.0 25.7 26.912000 19.1 14.5 21.7 34.5 27.8 37.0 18.5 14.1 16.1 34.5 26.9 28.012500 19.7 15.0 22.3 35.4 28.6 37.9 19.3 14.8 16.8 38.0 28.1 29.013000 20.2 15.4 22.9 36.3 29.4 38.7 20.2 15.5 17.4 37.5 29.3 30.1

NOTE: FOR PILES IN SAND, ADD ANTICIPATED SCOUR DEPTH. IF LOCAL SCOUR DATA ARE NOT AVAILABLE,ADD SCOUR DEPTH OF 4 FEET FOR FIRST ROW HOUSES, 2 FEET FOR INLAND HOUSES.

Design Tables A-13

TABLE A-4MAXIMUM UNBRACED HEIGHT OF PILES (FEET) IN 80 MPH WINDS

AND FLOOD FORCES

HORIZONTAL 8-INCH TIP PILESWIND LOADS 8X8 10X10 WITH EMBEDMENTS OF (POUNDS) PILES PILES 10 FT 20 FT 30 FT

400 8.1 10.2 9.8 11.1 12.2500 7.8 10.1 9.5 10.8 11.9600 7.6 9.9 9.2 10.5 11.7700 7.3 9.7 8.9 10.2 11.5800 7.1 9.5 8.6 10.0 11.2900 6.9 9.3 8.3 9.7 11.0

1000 6.6 9.2 8.0 9.5 10.81100 6.4 9.0 7.8 9.2 10.61200 6.2 8.8 7.5 9.0 10.31300 6.0 8.6 7.2 8.7 10.11400 5.8 8.5 7.0 8.5 9.91500 5.6 8.3 6.8 8.3 9.71600 5.4 8.1 6.5 8.1 9.51700 5.3 8.0 6.3 7.8 9.31800 5.1 7.8 6.1 7.6 9.11900 4.9 7.7 5.9 7.4 8.92000 4.8 7.5 5.7 7.2 8.72100 4.6 7.4 5.6 7.1 8.52200 4.5 7.2 5.4 6.9 8.32300 4.3 7.1 5.2 6.7 8.22400 4.2 6.9 5.1 6.5 8.0

NOTES: 1. WATER AND DEBRIS LOADS ASSOCIATED WITH THE INPUT WIND LOADS ARE INCLUDED IN THE CALCULATION OFUNBRACED HEIGHTS.

2. PILE HEIGHT ABOVE GRADE IS ASSUMED EQUAL TO DESIGN WATER HEIGHT. IF TOP OF PILE IS ABOVE BFE, USE THISTABLE OR CALCULATE HIGHER ALLOWABLE UNBRACED HEIGHT BY PROCEDURE IN APPENDIX D.


TABLE A-4 CONTINUEDMAXIMUM UNBRACED HEIGHT OF PILES (FEET) IN 90 MPH WINDS

AND FLOOD FORCES

HORIZONTAL 8-INCH TIP PILESWIND LOADS 8X8 10X10 WITH EMBEDMENTS OF (POUNDS) PILES PILES 10 FT 20 FT 30 FT

500 7.8 10.0 9.4 10.7 11.9600 7.5 9.8 9.1 10.4 11.8700 7.3 9.8 8.8 10.2 11.4800 7.0 9.5 8.5 9.9 11.2900 8.8 9.3 8.2 9.7 11.0

1000 6.6 9.1 8.0 9.4 10.71100 6.4 8.9 7.7 9.2 10.51200 6.2 8.8 7.4 8.9 10.31300 5.9 8.6 7.2 8.7 10.11400 5.8 8.4 6.9 8.5 9.91500 5.8 8.3 6.7 8.2 9.71600 5.4 8.1 6.5 8.0 9.41700 5.2 7.9 6.3 7.8 9.21800 5.0 7.8 6.1 7.6 9.11900 4.9 7.6 5.9 7.4 8.92000 4.7 7.5 5.7 7.2 8.72100 4.6 7.3 5.5 7.0 8.52200 4.4 7.2 5.3 6.8 8.32300 4.3 7.0 5.2 6.7 8.12400 4.2 6.9 5.0 6.5 8.02500 4.1 6.8 4.9 6.3 7.82600 4.0 6.6 4.8 6.2 7.62700 3.8 6.5 4.6 6.0 7.52800 3.7 6.4 4.5 5.9 7.32900 3.6 6.2 4.4 5.7 7.23000 3.5 6.1 4.3 5.6 7.03100 3.5 6.0 4.1 5.5 6.9



Design Tables A-15


AND FLOOD FORCESHORIZONTAL 8-INCH TIP PILESWIND LOADS 8X8 10X10 WITH EMBEDMENTS OF (POUNDS) PILES PILES 10 FT 20 FT 30 FT

600 7.3 9.7 8.9 10.2 11.5700 7.1 9.5 8.6 10.0 11.2800 6.9 9.3 8.3 9.7 11.0900 6.6 9.1 8.0 9.5 10.8

1000 6.4 9.0 7.8 9.2 10.61100 6.2 8.8 7.5 9.0 10.31200 6.0 8.6 7.3 8.7 10.11300 5.8 8.4 7.0 8.5 9.91400 5.6 8.3 6.8 8.3 9.71500 5.4 8.1 6.6 8.1 9.51600 5.3 8.0 6.3 7.9 9.31700 5.1 7.8 6.1 7.6 9.11800 4.9 7.6 5.9 7.4 8.91900 4.8 7.5 5.8 7.3 8.72000 4.6 7.3 5.6 7.1 8.52100 4.5 7.2 5.4 6.9 8.32200 4.4 7.1 5.2 6.7 8.22300 4.2 6.9 5.1 6.5 8.02400 4.1 6.8 4.9 6.4 7.82500 4.0 6.6 4.8 6.2 7.72600 3.9 6.5 4.7 6.1 7.52700 3.8 6.4 4.5 5.9 7.32800 3.7 6.3 4.4 5.8 7.22900 3.6 6.1 4.3 5.6 7.03000 3.5 6.0 4.2 5.5 6.93100 3.4 5.9 4.1 5.4 6.83200 3.3 5.8 4.0 5.3 6.63300 3.2 5.7 3.9 5.1 6.53400 3.2 5.6 3.8 5.0 6.43500 3.1 5.5 3.7 4.9 6.23600 3.0 5.4 3.6 4.8 6.13700 2.9 5.3 3.5 4.7 6.03800 2.9 5.2 3.4 4.6 5.9





AND FLOOD FORCESHORIZONTAL 8-INCH TIP PILESWIND LOADS 8x8 10x10 WITH EMBEDMENTS OF (POUNDS) PILES PILES 10 FT 20 FT 30 FT

900 6.3 8.8 7.6 9.1 10.41000 6.1 8.6 7.4 8.8 10.21100 5.9 8.5 7.1 8.6 10.01200 5.7 8.3 6.9 8.4 9.81300 5.5 8.1 6.6 8.1 9.51400 5.3 8.0 6.4 7.9 9.31500 5.2 7.8 6.2 7.7 9.21600 5.0 7.7 6.0 7.5 9.01700 4.8 7.5 5.8 7.3 8.81800 4.7 7.4 5.6 7.1 8.61900 4.5 7.2 5.5 6.9 8.42000 4.4 7.1 5.3 6.8 8.22100 4.3 6.9 5.2 6.6 8.02200 4.2 6.8 5.0 6.4 7.92300 4.0 6.7 4.9 6.3 7.72400 3.9 6.5 4.7 6.1 7.62500 3.8 6.4 4.6 6.0 7.42600 3.7 6.3 4.5 5.8 7.22700 3.6 6.2 4.3 5.7 7.12800 3.5 6.1 4.2 5.6 7.02900 3.4 5.9 4.1 5.4 6.83000 3.4 5.8 4.0 5.3 6.73100 3.3 5.7 3.9 5.2 6.53200 3.2 5.6 3.8 5.1 6.43300 3.1 5.5 3.7 5.0 6.33400 3.0 5.4 3.6 4.9 6.23500 3.0 5.3 3.6 4.7 6.13600 2.9 5.2 3.5 4.6 5.93700 2.8 5.1 3.4 4.6 5.83800 2.8 5.0 3.3 4.5 5.73900 2.7 4.9 3.3 4.4 5.64000 2.7 4.9 3.2 4.3 5.54100 2.6 4.8 3.1 4.2 5.44200 2.6 4.7 3.1 4.1 5.34300 2.5 4.6 3.0 4.0 5.24400 2.5 4.5 2.9 4.0 5.14500 2.4 4.5 2.9 3.9 5.14600 2.4 4.4 2.8 3.8 5.04700 2.3 4.3 2.8 3.8 4.94800 2.3 4.3 2.7 3.7 4.8

4900 2.2 4.2 2.7 3.6 4.75000 2.2 4.1 2.6 3.6 4.75100 2.2 4.1 2.6 3.5 4.65200 2.1 4.0 2.6 3.5 4.55300 2.1 3.9 2.5 3.4 4.45400 2.1 3.9 2.5 3.3 4.45500 2.0 3.8 2.4 3.3 4.3

NOTES: 1. WATER AND DEBRIS LOADS ASSOCIATED WITH THE INPUT WIND LOADSARE INCLUDED IN THE CALCULATION OF UNBRACED HEIGHTS.

2. PILE HEIGHT ABOVE GRADE IS ASSUMED EQUAL TO DESIGN WATERHEIGHT. IF TOP OF PILE IS ABOVE BFE, USE THIS TABLE OR CALCULATEHIGHER ALLOWABLE UNBRACED HEIGHT BY PROCEDURE IN APPENDIXD.

Design Tables A-17



700 6.9 9.3 8.4 9.8 11.0800 6.7 9.1 8.1 9.5 10.8900 6.5 9.0 7.8 9.3 10.6

1000 6.2 8.8 7.6 9.0 10.41100 6.0 8.6 7.3 8.8 10.21200 5.8 8.5 7.1 8.6 9.91300 5.7 8.3 6.8 8.3 9.71400 5.5 8.1 6.6 8.1 9.51500 5.3 8.0 6.4 7.9 9.31600 5.1 7.8 6.2 7.7 9.11700 5.0 7.7 6.0 7.5 8.91800 4.8 7.5 5.8 7.3 8.71900 4.7 7.4 5.6 7.1 8.62000 4.5 7.2 5.4 6.9 8.42100 4.4 7.1 5.3 6.7 8.22200 4.3 6.9 5.1 6.6 8.02300 4.1 6.8 5.0 6.4 7.92400 4.0 6.7 4.8 6.2 7.72500 3.9 6.5 4.7 6.1 7.52600 3.8 6.4 4.6 5.9 7.42700 3.7 6.3 4.4 5.8 7.22800 3.6 6.2 4.3 5.7 7.12900 3.5 6.0 4.2 5.5 6.93000 3.4 5.9 4.1 5.4 6.83100 3.3 5.8 4.0 5.3 6.73200 3.3 5.7 3.9 5.2 6.53300 3.2 5.6 3.8 5.0 6.43400 3.1 5.5 3.7 4.9 6.33500 3.0 5.4 3.6 4.8 6.23600 3.0 5.3 3.5 4.7 6.03700 2.9 5.2 3.5 4.6 5.93800 2.8 5.1 3.4 4.5 5.83900 2.8 5.0 3.3 4.4 5.74000 2.7 4.9 3.2 4.4 5.64100 2.7 4.8 3.2 4.3 5.54200 2.6 4.8 3.1 4.2 5.44300 2.6 4.7 3.1 4.1 5.34400 2.5 4.6 3.0 4.0 5.24500 2.5 4.5 2.9 4.0 5.14600 2.4 4.5 2.9 3.9 5.0


2. PILE HEIGHT ABOVE GRADE IS ASSUMED EQUAL TO DESIGN WATERHEIGHT. IF TOP OF PILE IS ABOVE BFE. USE THIS TABLE ORCALCULATE HIGHER ALLOWABLE UNBRACED HEIGHT BY PROCEDUREIN APPENDIX D.



AND FLOOD FORCES

HORIZONTAL 8-INCH TIP PILESWIND LOADS 8x8 10x10 WITH EMBEDMENTS OF (POUNDS) PILES PILES 10 FT 20 FT 30 FT

1000 5.9 8.5 7.1 8.6 10.01100 5.7 8.3 6.9 8.4 9.81200 5.5 8.1 6.7 8.2 9.51300 5.3 8.0 6.4 7.9 9.31400 5.2 7.8 6.2 7.7 9.21500 5.0 7.7 6.0 7.5 9.01600 4.8 7.5 5.9 7.3 8.81700 4.7 7.4 5.7 7.1 8.61800 4.6 7.2 5.5 7.0 8.41900 4.4 7.1 5.3 6.8 8.22000 4.3 6.9 5.2 6.6 8.12100 4.2 6.8 5.0 6.4 7.92200 4.1 6.7 4.9 6.3 7.72300 3.9 6.5 4.7 6.1 7.62400 3.8 6.4 4.6 6.0 7.42500 3.7 6.3 4.5 5.8 7.32600 3.6 6.2 4.4 5.7 7.12700 3.5 6.1 4.2 5.6 7.02800 3.4 5.9 4.1 5.4 6.82900 3.4 5.8 4.0 5.3 6.73000 3.3 5.7 3.9 5.2 6.63100 3.2 5.6 3.8 5.1 6.43200 3.1 5.5 3.7 5.0 6.33300 3.1 5.4 3.7 4.9 6.23400 3.0 5.3 3.6 4.8 6.13500 2.9 5.2 3.5 4.7 5.93600 2.9 5.1 3.4 4.6 5.83700 2.8 5.0 3.3 4.5 5.73800 2.7 4.9 3.3 4.4 5.63900 2.7 4.9 3.2 4.3 5.54000 2.6 4.8 3.1 4.2 5.44100 2.6 4.7 3.1 4.1 5.34200 2.5 4.6 3.0 4.1 5.24300 2.5 4.5 3.0 4.0 5.14400 2.4 4.5 2.9 3.9 5.14500 2.4 4.4 2.8 3.8 5.04600 2.3 4.3 2.8 3.8 4.9

4700 2.3 4.3 2.7 3.7 4.84800 2.3 4.2 2.7 3.6 4.74900 2.2 4.1 2.6 3.6 4.75000 2.2 4.1 2.6 3.5 4.65100 2.1 4.0 2.6 3.5 4.55200 2.1 3.9 2.5 3.4 4.45300 2.1 3.9 2.5 3.4 4.45400 2.0 3.8 2.4 3.3 4.35500 2.0 3.8 2.4 3.2 4.35600 2.0 3.7 2.4 3.2 4.25700 1.9 3.7 2.3 3.2 4.15800 1.9 3.6 2.3 3.1 4.15900 1.9 3.6 2.3 3.1 4.06000 1.9 3.5 2.2 3.0 4.06100 1.8 3.5 2.2 3.0 3.96200 1.8 3.4 2.2 2.9 3.86300 1.8 3.4 2.1 2.9 3.8


2. PILE HEIGHT ABOVE GRADE IS ASSUMED EQUAL TO DESIGN WATERHEIGHT. IF TOP OF PILE IS ABOVE BFE, USE THIS TABLE OR CALCULATEHIGHER ALLOWABLE UNBRACED HEIGHT BY PROCEDURE IN APPENDIXD.

Design Tables A-19



1200 5.3 8.0 6.5 7.9 9.31300 5.2 7.8 6.2 7.7 9.11400 5.0 7.6 6.0 7.5 8.91500 4.8 7.5 5.9 7.3 8.81600 4.7 7.4 5.7 7.1 8.61700 4.6 7.2 5.5 7.0 8.41800 4.4 7.1 5.3 6.8 8.21900 4.3 6.9 5.2 6.6 8.02000 4.2 6.8 5.0 6.4 7.92100 4.1 6.7 4.9 6.3 7.72200 3.9 6.5 4.7 6.1 7.62300 3.8 6.4 4.6 6.0 7.42400 3.7 6.3 4.5 5.8 7.22500 3.6 6.2 4.4 5.7 7.12600 3.5 6.1 4.3 5.6 7.02700 3.5 5.9 4.1 5.4 6.82800 3.4 5.8 4.0 5.3 6.72900 3.3 5.7 3.9 5.2 6.63000 3.2 5.6 3.8 5.1 6.43100 3.1 5.5 3.8 5.0 6.33200 3.1 5.4 3.7 4.9 6.23300 3.0 5.3 3.6 4.8 6.13400 2.9 5.2 3.5 4.7 5.93500 2.9 5.1 3.4 4.6 5.83600 2.8 5.0 3.4 4.5 5.73700 2.7 4.9 3.3 4.4 5.63800 2.7 4.9 3.2 4.3 5.53900 2.6 4.8 3.1 4.2 5.44000 2.6 4.7 3.1 4.1 5.34100 2.5 4.6 3.0 4.1 5.24200 2.5 4.5 3.0 4.0 5.24300 2.4 4.5 2.9 3.9 5.14400 2.4 4.4 2.9 3.8 5.04500 2.3 4.3 2.8 3.8 4.94600 2.3 4.3 2.7 3.7 4.84700 2.3 4.2 2.7 3.6 4.74800 2.2 4.1 2.7 3.6 4.7

4900 2.2 4.1 2.6 3.5 4.65000 2.1 4.0 2.6 3.5 4.55100 2.1 3.9 2.5 3.4 4.55200 2.1 3.9 2.5 3.4 4.45300 2.0 3.8 2.4 3.3 4.35400 2.0 3.8 2.4 3.3 4.35500 2.0 3.7 2.4 3.2 4.25600 1.9 3.7 2.3 3.2 4.15700 1.9 3.6 2.3 3.1 4.15800 1.9 3.6 2.3 3.1 4.05900 1.9 3.5 2.2 3.0 4.06000 1.8 3.5 2.2 3.0 3.96100 1.8 3.4 2.2 2.9 3.86200 1.8 3.4 2.1 2.9 3.86300 1.8 3.3 2.1 2.9 3.76400 1.7 3.3 2.1 2.8 3.76500 1.7 3.2 2.0 2.8 3.76600 1.7 3.2 2.0 2.7 3.66700 1.7 3.2 2.0 2.7 3.66800 1.6 3.1 2.0 2.7 3.56900 1.6 3.1 1.9 2.6 3.57000 1.6 3.1 1.9 2.6 3.47100 1.6 3.0 1.9 2.6 3.47200 1.6 3.0 1.9 2.5 3.37300 1.5 2.9 1.8 2.5 3.37400 1.5 2.9 1.8 2.5 3.3


2.PILE HEIGHT ABOVE GRADE IS ASSUMED EQUAL TO DESIGN WATERHEIGHT. IF TOP OF PILE IS ABOVE BFE, USE THIS TABLE OR CALCULATEHIGHER ALLOWABLE UNBRACED HEIGHT BY PROCEDURE IN APPENDIXD.


TABLE A-4.1MAXIMUM UNBRACED HEIGHT OF PILESSUPPORTING BREAKAWAY WALLS (FEET)

COMBINED 8-INCH TIP PILES LOAD 8X8 10x10 WITH EMBEDMENTS OFPER PILE (LB) PILES PILES 10 FT 20 FT 30 FT

700 17.6 34.3 21.0 28.8 38.3800 15.4 30.0 18.3 25.2 33.5900 13.7 26.7 16.3 22.4 29.8

1000 12.3 24.0 14.7 20.1 26.81100 11.2 21.8 13.3 18.3 24.41200 10.2 20.0 12.2 16.8 22.31300 9.5 18.5 11.3 15.5 20.61400 8.8 17.2 10.5 14.4 19.11500 8.2 16.0 9.8 13.4 17.91600 7.7 15.0 9.2 12.6 16.71700 7.2 14.1 8.6 11.8 15.81800 6.8 13.3 8.2 11.2 14.91900 6.5 12.6 7.7 10.6 14.12000 6.1 12.0 7.3 10.1 13.42100 5.9 11.4 7.0 9.6 12.82200 5.6 10.9 6.7 9.1 12.22300 5.3 10.4 6.4 8.8 11.62400 5.1 10.0 6.1 8.4 11.22500 4.9 9.6 5.9 8.1 10.72600 4.7 9.2 5.6 7.7 10.32700 4.6 8.9 5.4 7.5 9.92800 4.4 8.6 5.2 7.2 9.62900 4.2 8.3 5.1 6.9 9.23000 4.1 8.0 4.9 6.7 8.93100 4.0 7.7 4.7 6.5 8.63200 3.8 7.5 4.6 6.3 8.43300 3.7 7.3 4.4 6.1 8.13400 3.6 7.1 4.3 5.9 7.93500 3.5 6.9 4.2 5.8 7.73600 3.4 6.7 4.1 5.6 7.43700 3.3 6.5 4.0 5.4 7.23800 3.2 6.3 3.9 5.3 7.13900 3.2 6.2 3.8 5.2 6.94000 3.1 6.0 3.7 5.0 6.74100 3.0 5.9 3.6 4.9 6.54200 2.9 5.7 3.5 4.8 6.4

Design Tables A-21

TABLE A-5UPLIFT LOADS PER FOOT OF WALL (POUNDS) IN 80 MPH WINDS

ACTING ON ROOF CONNECTIONS OF ONE-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 67 74 81 88 96 104 113 122 131 141 15222 65 72 78 85 93 100 108 116 125 134 14424 64 70 76 83 90 97 104 112 120 128 13726 63 69 75 81 88 94 101 109 116 124 13228 62 68 73 80 86 92 99 106 113 120 12830 61 67 72 78 84 90 97 104 110 117 12532 60 66 71 77 83 89 95 102 108 115 12234 60 65 71 76 82 88 94 100 106 113 11936 59 64 70 75 81 87 93 99 105 111 11738 59 64 69 75 80 86 91 97 103 109 11640 58 63 69 74 79 85 91 96 102 108 114

ACTING ON ROOF CONNECTIONS OF TWO-STORY HOUSESLENGTH W I D T H (F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 78 86 94 102 111 120 130 140 151 162 17422 76 84 91 99 107 116 125 134 144 154 16524 75 82 89 97 104 112 121 130 139 148 15826 73 80 87 94 102 110 118 126 134 143 15328 72 79 86 93 100 107 115 123 131 139 14830 71 78 85 91 98 105 113 120 128 136 14432 71 77 83 90 97 104 111 118 126 133 14134 70 76 83 89 96 102 109 116 124 131 13936 69 76 82 88 95 101 108 115 122 129 13738 69 75 81 87 94 100 107 114 120 127 13540 68 74 81 87 93 99 106 112 119 126 133

ACTING ON FIRST FLOOR OF ONE-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 98 105 112 119 126 133 139 146 153 160 16722 90 96 103 109 115 122 128 134 140 146 15324 83 89 95 101 107 113 118 124 130 136 14126 78 83 89 94 100 105 111 116 121 127 13228 73 78 84 89 94 99 104 109 114 119 12430 69 74 79 84 89 94 99 103 108 113 11832 66 71 76 80 85 89 94 99 103 108 11234 63 68 72 77 81 86 90 94 99 103 10736 61 65 70 74 78 82 87 91 95 99 10338 59 63 67 71 76 80 84 88 92 96 9940 57 61 65 69 73 77 81 85 89 92 96


TABLE A-5 CONTINUEDUPLIFT LOADS PER FOOT OF WALL (POUNDS) IN 80 MPH WINDS, CONTINUED

ACTING ON SECOND FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 54 57 61 64 68 71 75 79 82 86 9022 45 48 51 54 57 61 64 67 70 74 7724 38 41 44 46 49 52 54 57 60 63 6626 33 35 37 39 42 44 46 49 52 54 5728 28 30 32 33 36 38 40 42 44 46 4930 24 25 27 28 30 32 34 36 38 40 4232 20 21 23 24 26 27 29 30 32 34 3634 17 18 19 20 21 23 24 26 27 29 3036 14 15 16 17 18 19 20 21 23 24 2638 12 12 13 14 15 15 17 18 19 20 2140 9 10 10 11 12 12 13 14 15 16 17

ACTING ON FIRST FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 189 199 208 218 227 236 245 253 261 270 27822 162 171 180 188 197 205 212 220 228 235 24224 141 149 157 164 172 179 186 193 200 206 21326 123 130 137 144 151 157 163 170 176 182 18828 108 114 121 127 133 139 144 150 156 161 16730 95 101 107 112 118 123 128 133 138 143 14932 84 89 95 99 104 109 114 119 123 128 13334 75 79 84 88 93 97 101 106 110 114 11836 66 71 75 79 83 87 91 94 98 102 10638 59 63 66 70 74 77 81 84 88 91 9540 53 56 59 62 66 69 72 75 79 82 85


Design Tables A-23

TABLE A-5 CONTINUEDUPLIFT LOADS PER FOOT OF WALL (POUNDS) IN 90 MPH WINDS


20 138 151 165 179 193 208 223 239 256 273 29122 135 148 161 174 187 201 216 231 246 262 27924 133 145 157 170 183 196 210 224 239 254 26926 131 143 155 167 180 192 206 219 233 247 26228 129 141 152 164 177 189 202 215 228 242 25630 128 139 151 162 174 186 199 211 224 237 25132 127 138 149 160 172 184 196 208 221 233 24634 125 136 148 159 170 182 194 206 218 230 24336 125 135 146 157 169 180 192 203 215 227 24038 124 134 145 156 167 178 190 201 213 225 23740 123 134 144 155 166 177 188 200 211 223 235

ACTING ON ROOF CONNECTIONS OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T ) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 153 167 182 197 212 228 245 262 280 299 31822 149 163 177 191 206 222 237 254 270 288 30524 147 160 173 187 202 216 231 247 262 279 29526 144 157 171 184 198 212 226 241 256 272 28728 143 155 168 181 195 208 222 236 251 266 28130 141 153 166 179 192 205 219 232 247 261 27632 140 152 164 177 190 203 216 229 243 257 27134 138 151 163 175 188 200 213 226 240 253 26736 137 149 161 174 186 198 211 224 237 250 26438 137 148 160 172 184 197 209 222 235 248 26140 136 147 159 171 183 195 208 220 233 245 258


20 162 173 183 193 202 212 221 231 240 249 25922 153 163 172 182 191 200 209 218 226 235 24424 146 155 164 173 182 190 199 207 215 224 23226 140 149 158 166 175 183 191 199 207 214 22228 135 144 153 161 169 177 184 192 200 207 21430 132 140 148 156 164 172 179 186 194 201 20832 128 137 145 152 160 167 175 182 189 196 20334 126 134 142 149 157 164 171 178 185 192 19936 124 131 139 147 154 161 168 175 182 188 19538 122 129 137 144 152 159 166 172 179 186 19240 120 128 135 143 150 157 164 170 177 183 189



ACTING ON SECOND FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T)(FEET) 20 22 24 28 28 30 32 34 38 38 40

20 106 112 118 123 129 134 140 145 151 156 16222 97 102 107 113 118 123 128 133 138 143 14824 89 94 99 104 109 113 118 122 127 132 13626 83 88 92 97 101 105 110 114 118 123 12728 78 82 87 91 95 99 103 107 111 118 11930 74 78 82 86 89 93 97 101 105 108 11232 70 74 78 81 85 88 92 96 99 103 10634 67 71 74 78 81 84 88 91 94 98 10136 64 68 71 74 78 81 84 87 90 94 9738 62 65 68 71 75 78 81 84 87 90 9340 60 63 66 69 72 75 78 81 84 87 90

ACTING ON FIRST FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T)(FEET) 20 22 24 28 28 30 32 34 38 38 40

20 288 303 317 330 343 356 368 380 392 403 41522 257 270 283 296 308 319 331 342 352 363 37324 231 244 256 267 278 289 300 310 320 330 33926 210 222 233 244 254 264 274 283 293 302 31128 193 204 214 224 234 243 252 261 270 279 28730 178 188 198 207 216 225 234 242 250 259 26732 165 175 184 193 202 210 218 226 234 241 24934 154 163 172 181 189 197 204 212 219 226 23436 145 154 162 170 177 185 192 199 206 213 22038 137 145 153 160 168 175 182 189 195 202 20840 129 137 145 152 159 166 172 179 185 192 198


Design Tables A-25



20 218 238 259 280 301 323 346 370 394 419 44522 214 233 253 273 294 315 336 359 381 405 42924 210 229 248 267 287 308 328 350 371 394 41726 207 225 244 263 282 302 322 342 363 385 40628 205 223 241 259 278 297 317 336 357 377 39830 202 220 238 256 274 293 312 331 351 371 39132 201 218 236 253 271 290 308 327 346 366 38534 199 216 234 251 269 287 305 323 342 361 38036 198 215 232 249 267 284 302 320 339 357 37638 196 213 230 247 265 282 300 317 336 354 37240 195 212 229 246 263 280 297 315 333 351 369

ACTING ON ROOF CONNECTIONS OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 236 257 279 302 325 349 373 399 425 452 47922 231 252 273 295 317 339 363 387 411 436 46224 227 247 268 289 310 332 354 377 400 424 44926 224 243 264 284 305 326 347 369 392 415 43828 221 240 260 280 300 321 342 363 385 407 42930 219 238 257 277 296 317 337 358 379 400 42232 217 235 254 274 293 313 333 353 374 395 41634 215 234 252 271 290 310 329 349 369 390 41036 213 232 250 269 288 307 326 346 366 386 40638 212 230 249 267 286 305 324 343 362 382 40240 211 229 247 265 284 302 321 340 359 379 398


20 234 248 262 275 288 300 313 325 337 349 36122 224 237 250 263 275 287 299 311 322 334 34524 216 229 242 254 266 277 289 300 311 322 33326 210 223 235 247 258 269 280 291 302 312 32328 205 218 229 241 252 263 274 285 295 305 31530 201 213 225 237 248 258 269 279 289 299 30932 198 210 222 233 244 255 265 275 285 295 30434 196 207 219 230 241 251 262 272 281 291 30036 193 205 217 228 239 249 259 269 279 288 29838 192 204 215 226 237 247 257 267 277 286 29540 190 202 214 225 235 246 256 265 275 284 294




20 165 173 181 189 197 204 212 219 227 234 24222 154 162 170 177 185 192 199 206 213 220 22724 146 154 161 168 175 182 189 195 202 208 21526 140 147 154 161 167 174 180 187 193 199 20528 134 141 148 155 161 167 173 179 185 191 19730 130 137 143 149 156 162 168 173 179 185 19132 126 133 139 145 151 157 163 168 174 180 18534 123 129 136 142 147 153 159 164 170 175 18036 120 127 133 138 144 150 155 161 166 171 17638 118 124 130 136 141 147 152 158 163 168 17340 116 122 128 134 139 145 150 155 160 165 170


20 399 419 438 456 473 490 506 522 538 553 56722 362 381 399 415 432 447 462 477 492 506 51924 332 350 367 382 398 413 427 441 454 467 48026 308 325 340 355 370 384 397 410 423 436 44828 288 303 318 333 347 360 373 385 397 409 42130 270 286 300 314 327 340 352 364 376 387 39832 256 270 284 297 310 322 334 346 357 368 37934 243 257 271 283 296 308 319 330 341 352 36236 233 246 259 271 283 295 306 317 327 337 34838 223 236 249 261 272 284 294 305 315 325 33540 215 228 240 252 263 274 284 295 305 314 324


Design Tables A-27


ACTING ON ROOF CONNECTIONS OF ONE-STORY HOUSESLENGTH W I D T H ( F E E T) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 306 334 362 391 421 451 483 515 548 582 61722 300 327 355 382 411 440 470 500 531 563 59624 295 322 348 375 403 431 459 488 518 549 58026 291 317 343 369 396 423 451 479 507 537 56728 288 313 338 364 390 417 444 471 499 527 55630 285 310 335 360 386 411 438 464 491 519 54732 282 307 331 356 381 407 433 459 485 512 53934 280 304 329 353 378 403 428 454 480 506 53336 278 302 326 350 375 400 424 450 475 501 52738 277 300 324 348 372 397 421 446 471 496 52240 275 298 322 346 370 394 418 443 468 493 518

ACTING ON ROOF CONNECTIONS OF TWO-STORY HOUSESLENGTH W I D T H (F E E T)(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 327 357 387 418 450 482 515 550 585 621 65822 321 350 379 409 439 470 502 534 567 601 63624 316 344 372 401 430 460 491 522 553 586 61926 311 339 366 395 423 452 481 511 542 573 60528 308 335 362 389 417 445 474 503 533 563 59430 305 331 358 385 412 440 468 496 525 554 58432 302 328 354 381 408 435 462 490 518 547 57634 300 325 351 378 404 431 458 485 513 541 56936 297 323 349 375 401 427 454 481 508 535 56338 296 321 346 372 398 424 450 477 503 531 55840 294 319 344 370 395 421 447 473 500 526 553

ACTING ON FIRST FLOOR OF ONE-STORY HOUSESLENGTH W I D T H (F E E T)(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 313 331 349 366 382 398 414 430 445 460 47522 302 320 336 353 369 384 399 414 429 443 45724 294 311 327 343 358 373 388 402 417 430 44426 287 304 320 336 351 365 380 394 407 421 43428 282 299 315 330 345 359 373 387 400 413 42630 278 295 310 326 340 354 368 382 395 408 42132 275 291 307 322 337 351 365 378 391 404 41634 273 289 305 320 334 348 362 375 388 401 41336 271 287 303 318 332 346 360 373 386 399 41138 269 286 301 316 331 345 359 372 385 397 41040 268 284 300 315 330 344 358 371 384 396 409




20 229 241 251 262 272 282 292 302 311 321 33022 218 229 239 249 259 269 278 287 296 305 31424 209 220 230 239 249 258 267 276 285 293 30226 202 212 222 232 241 250 258 267 275 284 29228 197 207 216 225 234 243 251 260 268 276 28430 192 202 211 220 229 237 246 254 262 270 27732 188 198 207 216 225 233 241 249 257 265 27234 185 194 204 212 221 229 237 245 253 260 26836 182 192 201 210 218 226 234 242 250 257 26438 180 189 198 207 216 224 232 239 247 254 26240 178 187 196 205 214 222 230 237 245 252 259

ACTING ON FIRST FLOOR OF TWO-STORY HOUSESLENGTH W I D T H (F E E T) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 522 548 572 595 617 639 659 679 699 718 73622 479 503 526 548 569 589 608 627 646 664 68124 444 467 489 510 530 549 567 585 603 620 63626 416 438 459 479 498 516 534 551 568 584 60028 392 414 434 453 471 489 506 523 539 554 56930 373 393 413 431 449 466 483 499 514 529 54432 356 376 395 413 430 447 463 478 493 508 52234 342 361 380 397 414 430 446 461 476 490 50436 330 349 367 384 400 416 432 446 461 475 48838 319 338 355 372 388 404 419 434 448 461 47540 310 328 346 362 378 393 408 423 436 450 463


Design Tables A-29


ACTING ON ROOF CONNECTIONS OF ONE-STORY HOUSESLENGTH W I D T H ( F E E T)(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 403 439 476 514 552 592 832 673 716 759 80422 395 430 466 502 539 577 615 655 695 736 77824 389 423 458 493 529 565 602 640 679 718 75826 384 417 451 485 520 556 592 628 665 703 74228 379 412 445 479 513 548 583 618 654 691 72830 375 408 440 474 507 541 575 610 645 681 71732 372 404 436 469 502 535 569 603 637 672 70734 369 401 433 465 497 530 563 597 630 665 69936 367 398 430 461 493 526 558 591 625 658 69238 364 395 427 458 490 522 554 587 619 653 68640 362 393 424 455 487 518 550 582 615 648 681


20 428 466 506 546 586 628 671 715 760 806 85322 420 457 495 533 573 613 653 695 738 781 82624 413 449 486 524 562 600 640 680 721 762 80526 407 443 479 516 553 590 628 667 706 747 78728 403 438 473 509 545 582 619 657 695 734 77330 399 433 468 503 539 575 611 648 685 723 76132 395 429 464 498 533 568 604 640 677 714 75134 392 426 460 494 528 563 598 634 670 706 74336 390 423 456 490 524 558 593 628 663 699 73538 387 420 453 487 520 554 589 623 658 693 72940 385 418 451 484 517 551 585 619 653 688 723

ACTING ON FIRST FLOOR OF ONE-STORY HOUSESLENGTH W I D T H (F E E T) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 400 423 444 465 485 505 525 544 563 581 60022 388 410 431 451 471 490 509 527 545 563 58024 379 400 421 441 460 479 497 515 532 549 56626 372 393 413 433 452 470 488 506 523 539 55628 367 388 408 427 446 464 482 499 516 532 54830 363 383 404 423 441 460 477 494 511 527 54332 359 380 400 420 438 456 474 491 507 523 53934 357 378 398 418 436 454 472 488 505 521 53736 355 376 397 416 435 453 470 487 504 520 53538 354 375 396 415 434 452 469 486 503 519 53540 353 375 395 415 433 452 469 486 503 519 535




20 300 314 328 342 354 367 379 392 404 416 42722 288 302 315 328 340 353 364 376 388 399 41024 278 292 305 317 330 341 353 364 375 386 39726 271 284 297 309 321 333 344 355 366 376 38728 265 278 290 303 314 326 337 348 358 368 37930 260 273 285 297 309 320 331 342 352 362 37232 256 269 281 293 305 316 327 337 348 358 36734 253 266 278 290 301 313 323 334 344 354 36436 240 263 275 287 299 310 321 331 341 351 36138 248 261 273 285 297 308 318 329 339 349 35940 246 259 271 283 295 306 317 327 337 347 357

ACTING ON FIRST FLOOR OF TWO-STORY HOUSESLENGTH W I D T H (F E E T) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 657 688 719 747 775 801 826 851 875 898 92122 607 637 666 693 709 744 768 792 814 836 85824 567 596 623 649 674 698 721 744 765 787 80726 534 562 588 614 638 661 683 705 726 746 76628 507 534 560 584 608 630 652 673 693 713 73230 485 511 536 560 583 605 626 646 666 685 70332 466 492 516 539 562 583 604 624 643 662 68034 450 475 499 522 544 565 585 605 623 642 66036 436 461 484 507 528 549 569 588 607 625 64338 424 449 472 494 515 536 555 574 593 611 62840 414 438 461 483 504 524 544 563 581 598 616


Design Tables A-31


ACTING ON ROOF CONNECTIONS OF ONE-STORY HOUSESLENGTH W I D T H ( F E E T)(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 508 553 600 647 695 744 794 846 898 852 100822 498 542 587 633 679 726 774 823 873 924 97724 490 533 577 621 666 712 758 805 853 902 95226 484 526 569 612 655 700 745 791 837 884 93228 478 520 562 604 647 690 734 778 824 869 91630 474 514 556 597 639 682 725 768 812 857 90232 469 510 550 591 633 675 717 759 803 846 89134 466 506 546 586 627 668 710 752 794 837 88136 463 502 542 582 622 663 704 745 787 829 87238 460 499 538 578 618 658 699 740 781 822 86440 457 496 535 575 614 654 694 735 775 816 858


20 537 585 634 684 735 787 840 894 950 1007 106522 527 574 621 669 718 768 819 871 923 978 103324 519 564 610 657 705 753 802 852 902 954 100726 512 557 602 647 693 740 788 836 885 935 98628 506 550 594 639 684 730 776 823 871 920 96930 501 544 588 632 676 721 767 813 859 906 95432 497 539 582 626 669 714 758 803 849 895 94234 493 535 578 620 664 707 751 795 840 886 93136 490 531 573 616 658 701 745 789 833 877 92238 487 528 570 612 654 696 739 782 826 870 91440 484 525 566 608 650 692 734 777 820 864 907

ACTING ON FIRST FLOOR OF ONE-STORY HOUSESLENGTH W I D T H (F E E T) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 495 522 548 573 598 622 645 668 691 713 73522 481 508 533 558 582 605 628 650 672 693 71424 471 497 523 547 570 593 615 537 658 679 69926 464 490 515 539 562 584 606 627 648 668 68828 458 484 509 533 556 578 600 621 641 661 68130 454 480 505 529 552 574 595 616 637 656 67632 451 477 502 526 549 571 593 613 634 653 67334 449 475 500 524 547 569 591 612 632 652 67136 448 474 499 523 546 569 590 611 631 651 67038 447 473 498 522 546 568 590 611 632 651 67140 446 473 498 523 546 569 591 612 632 652 672



ACTING ON SECOND FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T ) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 377 395 412 428 444 460 475 490 504 519 53322 364 381 398 413 429 444 458 473 487 501 51424 353 370 387 402 417 432 446 460 474 487 50026 345 362 378 393 408 423 437 450 464 477 49028 339 355 371 387 402 416 430 443 456 469 48230 334 350 366 382 396 410 424 437 451 463 47632 330 346 362 377 392 406 420 433 446 459 47134 326 343 359 374 389 403 417 430 443 456 46836 324 341 357 372 387 401 415 428 441 453 46638 322 339 355 370 385 399 413 426 439 452 46440 320 337 353 369 384 398 412 425 438 451 463


20 803 842 878 913 946 978 1008 1038 1067 1095 112222 746 783 817 851 882 913 942 970 998 1024 105024 700 735 769 801 831 861 889 916 942 968 99326 662 697 730 761 790 818 846 872 898 922 94628 632 665 697 727 756 784 810 836 861 885 90830 606 639 670 700 728 755 781 806 831 854 87732 585 617 648 677 705 731 757 781 805 828 85134 567 599 629 657 685 711 736 760 784 807 82936 552 583 613 641 668 694 719 743 766 789 81038 538 569 599 627 653 679 704 728 751 773 79540 527 558 587 614 641 667 691 715 738 760 782


Design Tables A-33



20 621 677 733 790 849 908 969 1032 1095 1161 122822 610 663 718 773 830 887 945 1005 1066 1128 119124 600 653 706 760 814 870 926 983 1042 1101 116226 592 644 696 748 802 856 910 966 1022 1080 113828 585 636 687 739 791 844 897 951 1006 1062 111830 580 630 680 731 782 834 886 939 993 1047 110232 575 624 674 724 774 825 877 929 981 1034 108834 570 619 668 718 767 818 868 920 971 1023 107636 566 615 663 712 762 811 861 912 963 1014 106638 563 611 659 708 756 805 855 905 955 1006 105740 580 608 655 703 752 800 849 899 948 998 1049

ACTING ON ROOF CONNECTIONS OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T )(FEET) 20 22 24 26 28 30 32 34 36 38 40

20 655 714 773 834 895 958 1022 1088 1155 1224 129522 643 700 757 818 875 936 997 1060 1124 1189 125624 633 688 744 801 859 917 977 1037 1099 1161 122526 625 879 734 789 846 902 960 1019 1078 1139 120028 618 671 725 779 834 890 946 1004 1061 1120 118030 612 664 717 771 825 879 935 991 1047 1104 116232 606 658 711 763 817 870 925 980 1035 1091 114834 602 653 705 757 810 863 916 970 1025 1080 113536 598 649 700 751 803 856 909 962 1015 1070 112438 594 645 695 746 798 850 902 954 1007 1061 111540 591 841 691 742 793 844 896 948 1000 1053 1106


20 597 629 660 690 719 747 775 802 829 855 88122 582 613 644 673 702 729 756 783 808 834 85924 571 602 632 661 689 716 743 769 794 818 84326 563 594 624 653 681 707 733 759 784 808 83128 557 589 618 647 675 701 727 752 777 801 82430 553 584 614 643 671 697 723 748 772 796 81932 550 582 612 640 668 695 721 746 770 794 81734 548 580 610 639 667 694 720 745 769 793 81636 547 579 609 638 866 693 720 745 769 793 81638 546 578 609 638 667 694 720 746 770 794 81840 546 578 609 639 668 695 722 747 772 796 820



ACTING ON SECOND FLOOR OF TWO-STORY HOUSESLENGTH W I D T H ( F E E T ) (FEET) 20 22 24 26 28 30 32 34 36 38 40

20 460 482 502 522 541 559 577 595 613 630 64722 445 466 486 506 524 542 560 577 594 610 62724 434 455 475 494 512 530 547 564 580 596 61226 425 446 466 485 503 520 537 554 570 585 60128 419 439 459 478 496 513 530 546 562 578 59330 413 434 454 472 490 508 524 541 557 572 58732 409 430 449 468 486 504 521 537 553 568 58334 406 427 446 465 483 501 518 534 550 565 58036 403 424 444 463 481 499 516 532 548 564 57938 401 422 442 462 480 498 515 531 547 563 57840 400 421 441 461 479 497 514 531 547 563 578


20 961 1007 1050 1092 1131 1169 1205 1240 1274 1307 133922 895 940 981 1021 1059 1095 1130 1163 1196 1227 125824 843 886 926 965 1001 1036 1070 1102 1133 1164 119326 801 843 882 919 955 989 1021 1053 1083 1113 114128 767 807 845 882 916 950 982 1012 1042 1071 109930 738 778 815 851 885 918 949 979 1008 1037 106432 714 753 790 825 859 891 922 952 981 1008 103634 694 732 769 804 837 869 899 929 957 985 101236 876 715 751 785 818 850 880 909 938 965 99238 662 699 735 770 802 834 864 893 921 948 97540 649 687 722 756 789 820 850 879 907 934 961


Design Tables A-35

TABLE A-6

UPLIFT LOADS PER PILE (POUNDS) IN 80 MPH WINDSFOR ONE-STORY HOUSES

WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40

LENGTH NUMBER (FEET) OF PILES 3 3 4 4 4 4 5 5 5 6

20 3 695 836 627 737 853 974 682 779 882 73524 3 655 785 588 689 794 905 636 724 816 68024 4 549 659 495 580 670 765 536 612 691 57628 4 527 631 473 554 637 725 510 580 654 54532 4 518 617 463 540 620 704 496 563 633 52736 4 517 614 461 536 614 695 491 556 623 51932 5 438 522 392 458 526 597 421 478 538 44836 5 434 517 387 451 518 586 414 469 527 43940 5 436 517 388 451 516 583 413 466 522 43540 6 374 444 333 388 444 502 355 402 450 375


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 1759 2111 1583 1852 2127 2408 1702 1926 2157 179724 3 1419 1700 1275 1489 1708 1933 1367 1546 1730 144224 4 1296 1555 1166 1363 1565 1771 1252 1417 1586 132228 4 1075 1286 965 1126 1291 1461 1033 1169 1308 109032 4 903 1078 808 942 1079 1219 863 975 1091 90936 4 764 909 682 793 907 1024 725 819 915 76332 5 815 974 730 852 976 1104 781 883 988 82336 5 694 827 620 722 826 933 661 747 835 69640 5 593 704 528 613 701 791 561 633 707 58940 6 538 640 480 558 638 720 511 576 644 537



TABLE A-6 CONTINUED

UPLIFT LOADS PER PILE (POUNDS) IN 90 MPH WINDS


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 1861 2381 1786 2220 2700 3226 2160 2581 3039 253324 3 1763 2232 1674 2063 2490 2955 1992 2364 2767 230624 4 1475 1879 1410 1746 2116 2520 1693 2016 2368 197328 4 1424 1797 1348 1656 1993 2360 1595 1888 2206 183832 4 1405 1759 1319 1609 1924 2266 1539 1813 2107 175636 4 1408 1750 1312 1590 1891 2214 1513 1771 2049 170832 5 1186 1489 1117 1366 1639 1934 1311 1547 1802 150236 5 1181 1473 1105 1343 1601 1880 1281 1504 1743 145340 5 1191 1475 1106 1336 1585 1852 1268 1482 1710 142540 6 1022 1268 951 1151 1368 1601 1095 1281 1481 1234


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 3338 4160 3120 3783 4494 5252 3595 4202 4848 404024 3 2876 3573 2679 3241 3841 4482 3073 3586 4131 344324 4 2535 3155 2366 2866 3401 3973 2721 3178 3665 305528 4 2242 2782 2086 2521 2986 3483 2389 2786 3209 267432 4 2030 2511 1883 2270 2683 3124 2146 2499 2873 239536 4 1872 2308 1731 2081 2454 2852 1963 2281 2619 218332 5 1775 2199 1649 1990 2355 2743 1884 2195 2525 210536 5 1632 2015 1511 1819 2148 2499 1719 1999 2297 191440 5 1523 1874 1405 1687 1988 2308 1591 1847 2119 176640 6 1341 1652 1239 1489 1756 2040 1405 1632 1874 1561


Design Tables A-37

TABLE A-6 CONTINUED


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 2596 3291 2468 3044 3676 4365 2941 3492 4089 340824 3 2527 3169 2377 2904 3477 4098 2782 3278 3814 317824 4 2085 2630 1973 2423 2914 3449 2331 2759 3221 268428 4 2061 2575 1931 2352 2809 3302 2247 2642 3066 255532 4 2077 2574 1931 2334 2769 3236 2215 2589 2988 249036 4 2121 2610 1957 2351 2773 3223 2218 2579 2962 246832 5 1738 2161 1621 1965 2338 2739 1870 2191 2535 211336 5 1764 2178 1633 1968 2327 2712 1862 2170 2498 208240 5 1807 2217 1663 1992 2344 2719 1875 2175 2493 207840 6 1542 1896 1422 1707 2012 2337 1609 1870 2146 1789


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 4508 5594 4195 5066 5996 6986 4797 5589 6429 535724 3 4008 4951 3714 4469 5273 6127 4218 4901 5625 468724 4 3472 4300 3225 3889 4597 5350 3678 4280 4918 409928 4 3164 3903 2927 3518 4146 4813 3317 3851 4415 367932 4 2955 3630 2723 3262 3833 4438 3067 3551 4062 338536 4 2813 3442 2582 3082 3612 4171 2889 3337 3809 317432 5 2551 3139 2354 2824 3324 3853 2659 3082 3530 294136 5 2416 2962 2222 2657 3118 3605 2494 2884 3296 274740 5 2323 2838 2128 2537 2969 3425 2376 2740 3125 260440 6 2025 2477 1858 2217 2597 2998 2078 2399 2737 2281



TABLE A-6 CONTINUED


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 3409 4297 3223 3955 4755 5624 3804 4499 5251 437624 3 3373 4206 3154 3833 4569 5362 3655 4290 4971 414224 4 2759 3461 2596 3171 3798 4476 3038 3580 4165 347128 4 2766 3436 2577 3122 3711 4344 2969 3475 4017 334832 4 2821 3477 2608 3136 3703 4309 2963 3447 3964 330336 4 2909 3561 2671 3193 3749 4339 2999 3472 3972 331032 5 2349 2904 2178 2628 3111 3629 2489 2903 3346 278836 5 2409 2958 2219 2660 3131 3633 2505 2906 3333 277740 5 2490 3039 2280 2718 3184 3677 2547 2942 3359 279940 6 2118 2591 1943 2322 2724 3151 2179 2521 2883 2402


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 5803 7179 5384 6486 7659 8903 6127 7123 8177 681524 3 5260 6477 4858 5828 6857 7946 5485 6357 7277 606424 4 4510 5568 4176 5021 5920 6873 4736 5498 6305 525428 4 4184 5142 3857 4620 5429 6285 4344 5028 5750 479232 4 3978 4869 3652 4359 5106 5893 4084 4714 5378 448136 4 3854 4697 3523 4190 4893 5631 3914 4505 5126 427132 5 3408 4179 3135 3747 4395 5080 3516 4064 4641 386736 5 3284 4010 3008 3583 4191 4830 3353 3864 4402 366840 5 3209 3904 2928 3478 4055 4661 3244 3729 4238 353140 6 2782 3389 2542 3022 3527 4058 2822 3247 3693 3077


Design Tables A-39

TABLE A-6 CONTINUED

UPLIFT LOADS PER PILE (POUNDS) IN 120 MPH WINDS


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 4298 5399 4049 4953 5937 7003 4749 5602 6522 543524 3 4299 5340 4005 4851 5764 6746 4611 5396 6237 519824 4 3497 4370 3277 3991 4764 5600 3812 4480 5198 433228 4 3537 4378 3283 3965 4698 5484 3758 4387 5059 421632 4 3635 4464 3348 4015 4726 5484 3781 4387 5031 419236 4 3772 4603 3452 4115 4817 5561 3854 4449 5077 423132 5 3017 3717 2788 3353 3957 4603 3166 3683 4233 352736 5 3114 3812 2859 3417 4011 4641 3209 3713 4247 353940 5 3236 3939 2954 3513 4103 4727 3283 3781 4307 358940 6 2749 3352 2514 2994 3504 4042 2803 3234 3688 3073


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 7219 8915 6686 8040 9478 11002 7582 8802 10091 840924 3 6631 8146 6110 7315 8590 9937 6872 7949 9085 757124 4 5645 6955 5216 6260 7368 8539 5894 6832 7822 651828 4 5300 6499 4874 5827 6834 7896 5467 6317 7211 600932 4 5098 6225 4668 5560 6498 7485 5198 5988 6817 568136 4 4993 6071 4553 5403 6295 7229 5036 5784 6567 547232 5 4347 5318 3988 4757 5569 6423 4455 5138 5857 488136 5 4233 5157 3868 4598 5365 6170 4292 4936 5612 467640 5 4179 5072 3804 4507 5243 6014 4194 4811 5456 454740 6 3610 4388 3291 3903 4546 5219 3636 4175 4739 3949



TABLE A-6 CONTINUED


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 5266 6597 4948 6038 7222 8503 5778 6802 7905 658824 3 5306 6574 4930 5958 7064 8251 5651 6601 7615 634624 4 4300 5359 4019 4882 5816 6822 4653 5458 6322 526828 4 4376 5403 4052 4882 5772 6724 4618 5379 6191 516032 4 4520 5539 4154 4970 5839 6762 4671 5409 6192 516036 4 4710 5736 4302 5117 5979 6890 4784 5512 6280 523332 5 3744 4602 3452 4141 4878 5663 3903 4530 5198 433136 5 3882 4741 3556 4241 4968 5737 3974 4590 5241 436740 5 4048 4917 3688 4377 5103 5868 4083 4695 5338 444840 6 3435 4179 3135 3726 4351 5011 3481 4009 4565 3804


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40


20 3 8760 10802 8102 9730 11457 13285 9166 10628 12173 1014424 3 8122 9962 7472 8932 10475 12102 8380 9682 11052 921024 4 6880 8464 6348 7608 8943 10353 7154 8282 9472 789328 4 6514 7975 5981 7140 8361 9648 6689 7718 8801 733432 4 6317 7699 5774 6866 8013 9217 6410 7373 8383 698636 4 6232 7565 5674 6722 7820 8968 6256 7174 8134 677832 5 5369 6556 4917 5856 6845 7884 5476 6307 7179 598336 5 5266 6405 4804 5701 6642 7628 5314 6102 6928 577340 5 5233 6342 4756 5626 6536 7485 5228 5988 6781 565140 6 4511 5474 4105 4862 5653 6481 4523 5185 5876 4897


Design Tables A-41

TABLE A-6 CONTINUED


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40

LENGTH NUMBER(FEET) OF PILES 3 3 4 4 4 4 5 5 5 6

20 3 6311 7890 5918 7209 8609 10121 6887 8097 9398 783224 3 6393 7906 5929 7153 8468 9875 6774 7900 9102 758524 4 5167 6426 4820 5845 6952 8142 5561 6514 7535 627928 4 5281 6509 4882 5871 6931 8063 5545 6450 7414 617832 4 5476 6698 5024 6001 7039 8141 5632 6513 7445 620436 4 5723 6958 5219 6199 7234 8324 5787 6659 7577 631432 5 4529 5557 4168 4993 5872 6807 4698 5446 6239 519936 5 4710 5743 4308 5130 6001 6921 4800 5537 6314 526140 5 4925 5974 4480 5310 6183 7100 4946 5880 6451 537640 6 4175 5073 3804 4516 5267 6057 4213 4846 5510 4592


WIDTH (FEET) 20 24 24 28 32 36 32 36 40 40

LENGTH NUMBER(FEET) OF PILES 3 3 4 4 4 4 5 5 5 6

20 3 10424 12840 9630 11554 13593 15749 10875 12599 14420 1201624 3 9731 11922 8942 10678 12510 14440 10008 11552 13175 1098024 4 8213 10092 7569 9063 10642 12310 8514 9848 11253 937828 4 7824 9568 7176 8556 10010 11539 8008 9231 10516 876332 4 7632 9291 6968 8276 9648 11086 7718 8869 10073 839436 4 7570 9178 6883 8146 9466 10844 7573 8675 9826 818832 5 6471 7893 5920 7042 8222 9461 6578 7569 8607 717336 5 6381 7751 5814 6892 8020 9201 6416 7361 8348 695740 5 6372 7712 5784 6834 7931 9073 6344 7259 8211 684340 6 5484 6646 4985 5896 6849 7843 5479 6274 7104 5920



TABLE A-7

CAPACITY PER BOLT (POUNDS) OF FLOOR BEAM CONNECTIONS

Connection Type 1--Use 100 percent of downward load

Type of Bolt Diameter in Inches Connection 5/8 3/4 7/8 1 1-1/4 Spiked Grid - 3800 - 4100 -

Beam to Unnotched Pile 700 930 1100 1250 1500

Connection Type II--Use greater of the following: 100 percent of uplift loador

50 percent of downward load

Type of Bolt Diameter in Inches Connection 5/8 3/4 7/8 1 1-1/4 Notched Pile 700 880 990 1080 1270

Spaced Beam 970 1080 1190 1300 1520

Steel Plate (beam) 700 930 1100 1250 1500 Insert (pile) 1200 1720 2335 3070 4770

Gusset (beam) - 1450 2300 3000 4200 (pile) - 3700 5000 6500 10200

Strap (beam) - 1450 2300 3000 4200(pile) - 3700 5000 6500 10200

Design Tables A-43

TABLE A-8CONCRETE MASONRY UNIT PIERS

REINFORCING REQUIREMENTS Without Inspection 100 MPH 110 MPH WIND 120 MPH WINDS 130 MPH WINDSCMU f'm = 1500 psi 7'CLR 10'CLR 12' CLR 7'CLR 10' CLR 12' CLR 7' CLR 10' CLR 12' CLR 7' CLR 10' CLR 12' CLR

12" x 16"* 4- #8 4- #11 4- #9 4- #10 4- #108- #7 8- #8 8- #8

16" x 16" 4- #8 8- #10 4- #9 8- #8 4-#108- #7 8- #8 12- #7 8-#9

24" x 24" 4- #6 4- #10 8- #10 4- #6 4- #10 8- #11 4- #7 4- #11 4-#8 8-#108- #5 8- #8 8- #5 8- #9 8- #6 8- #9 8-#7

*Steel for 12" x 16" CMU Piers is based on moment acting about major axis (t = 16").

TIE REQUIREMENTS

12" x 16" CMU PIER 16" x 16" CMU PIER 24" x 24" CMU PIER 7'CLR 10'CLR 12' CLR 7'CLR 10' CLR 12' CLR 7' CLR 10' CLR 12' CLR

#2T @ 12" #2T @ 6" #2T @ 6" #2T @ 12" #2T @ 12" #2T @ 6" Use four standard truss type masonryreinforcing corner pieces every course.

CMU PIER TYPES


TABLE A-9CONCRETE PIERS

REINFORCING REQUIREMENTS

f'c = 2.5 ksi 100 MPH WIND 110 MPH WIND 120 MPH WIND 130 MPH WINDfy = 40 ksi 7'CLR 10'CLR 12' CLR 7'CLR 10' CLR 12' CLR 7' CLR 10' CLR 12' CLR 7' CLR 10' CLR 12' CLR

12" x 12" 4- #8 4- #11* - 4- #9 8- #10 - 4- #10 - - 4- #10 - -8- #7 8- #9* 8- #7 8- #8* 8- #8

12- #6 12- #8* 12- #6 12- #7* 12- #7

16" x 16" 4- #8 4- #10 4- #11 4- #8 4- #10 8- #10 4- #8 4- #11 8- #11* 4- #9 8- #10 8- #11*8- #6 8- #8 8- #9 8- #7 8- #9 12- #9* 8- #7 8- #9 12- #9* 8- #7 12- #8 12- #10*

12- #7 12- #6 12- #7 12- #6 12- #8 12- #6

f'c = 2.5 ksify = 60 ksi

12" x 12" 4- #7 4- #9 - 4- #8 4- #10 - 4- #8 4- #11* - 4- #9 - -8- #6 8- #8* 8- #6 8- #8* 8- #7 8- #9* 8- #7

12- #7* 12- #7* 12- #6 12- #8* 12- #6

16" x 16" 4- #7 4- #8 4- #10 4- #7 4- #9 4- #10 4- #7 4- #9 4- #11 4- #7 4- #10 4- #118- #5 8- #7 8- #8 8- #5 8- #7 8- #8 8- #6 8- #8 8- #9 8- #6 8- #8 8- #9

12- #6 12- #7 12- #7 12- #5 12- #6 12- #8 12- #5 12- #7 12- #8

*Steel percentage exceeds 4%.

Tie Requirements 12" x 12" Pier Pier 16" x 16" Pier Concrete Pier Types

For #5 Longitudinal Bars #3T @ 10" #3T @ 10"For #6 " " #3T @ 12" #3T @ 12"For #7 " " #3T @ 12" #3T @ 14"For #8 thru #10 " " #3T @ 12" #3T @ 16"For #11 " " #4T @ 12" #4T @ 16"

Design Tables A-45

CONCRETE PIER NOTES:1. Indicated steel area to be placed in each

column face subject to moment.2. Steel for a 16-inch by 12-inch column based

on moment acting only about section’s majoraxis (t=16)

3. Use No. 3 ties at 16 inches on center.4. Normally, use square piers with the same

reinforcement in all faces

Figure A-2. Concrete pier cross section.

GRADE BEAM

As = A’s = 0.62 in2 (2-#5 Top and Bottom)

f’c = 3000 psify = 60000 psi

Provide dowels from grade beam into pier tomatch pier vertical reinforcing

SLABFour inch slab with 6"x6" welded wire fabric(No.6/No.6) placed on top of slab

Figure A-3. Grade beams and slabs.


TABLE A-10

FASTENER CAPACITIES IN SHEAR(nails, screws, and dowel pins)

NAILS (WOOD STUD WALL) SCREWS--SELF TAPPING (METAL STUD WALL)

Working Ultimate Screw Working UltimateNail Capacity (lb) Capacity (lb) a Size (In) Capacity (lb) Capacity (lb)* Size Lateral Toe Nail Lateral Toe Nail No. 6 153 3828d 78 65 390 325 S-12

(57)b (285) dia =0.106

10d 94 78 470 390(85) (425) Source: Sweets 5.3/in P.10

*Safety factor = 2.512d 94 78 470 390

DOWEL PINS (MASONRY WALL)16d 107 89 535 445

Dowel Depth of Concrete Ultimate____________________ Size Penetration Strength CapacitySource: Timber Construction Manual, AITC, 1974 (in) (in) (psi) (lb) aSafety factor =5 dia=0.145 1-1/8 3,000 1,966

bReduced values used in this report because 8d and 10d nails Source: Laboratory Test data on Hilti Fasteners by Abbotdo not develop full strength in two 2x4’s. A. Hanks, 1972.

Design Tables A-47

TABLE A-11FASTENER SCHEDULE FOR BREAKAWAY WALLS

NAILS (WOOD STUD WALL)

Breakaway Wall Height (feet)

6 7 8 9 Nail Size 8d 10d 12d 16d 8d 10d 12d 16d 8d 10d 12d 16d 8d 10d 12d 16d Pile Spacing (feet)

8 8/15 6/10 5/9 - 9/17 6/12 6/10 5/9 - 7/13 7/12 6/10 - 8/15 7/14 7/1210 10/19 7/13 6/12 6/10 - 8/15 7/13 6/12 - 9/17 8/15 7/14 - 10/19 9/17 8/1512 - 8/16 8/14 7/12 - 10/18 9/16 8/14 - - 10/19 9/17 - - - 10/19

NOTES:1) Table indicates the range of total (top and bottom) nails that will result in a wall with a design safe loading resistance between

10 and 20 PSF.2) Where an odd number of nails is shown, put the extra nail at the bottom.3) Values for other wall heights or pile spacings can be interpolated.

Example: A 7-foot-high breakaway wall installed between piles spaced 10 feet apart should be fastened with no less than 8(4 top, 4 bottom)and no more than 15 (7 top, 8 bottom) 10d nails.

SCREWS (METAL STUD WALL)

Breakaway Wall Height (feet)

6 7 8 9

Pile Spacing (feet)

8 4/5 4/6 4/7 5/810 4/6 5/8 5/9 6/1112 4/8 6/10 6/11 7/13

NOTES:

1) Table is used in same manner as nail table above.2) Based on No. 6, S-12 screws.

Bracing B-1

Appendix B

BRACING

Chapter 4 included a discussion of pile bracing. It waspointed out that in many cases, particularly when the designwind speed is more than 100 mph, at least simple diagonalbracing (Figure 4-3 1) or knee braces (Figure 4-33) may berequired. For high elevated houses or extreme design windspeeds truss bracing may be needed, as shown in Figures 4-38 and 4-39.

A truss bracing system consists of two types of members,referred to as diagonals and struts. These members can besized and connected to the piles using the informationprovided in this appendix. The design loads, which themembers and connections must withstand, are obtained byadding together the horizontal wind load, Table A-2, for theappropriate wind speed, number of stories, house dimensions,and number of piles, with the horizontal water load, Table B-1,for the appropriate wind speed, location, size of pile, and pileheight above grade required. Once the combined horizontalload acting on one pile is determined, Table B-2 may be usedto determine the design load for diagonals and struts.

In order to select the proper diagonal design load fromTable B-2, one needs to compute the A/B ratio for trussesperpendicular to the shoreline. A and B are the vertical andhorizontal distances between connections of the diagonal,respectively, as shown in Figure B-1. Design loads fordiagonals and their connections are presented in Table B-2 forA/B ratios ranging from 1.0 to 1.5.

The procedures for sizing diagonals, struts, and theirconnections to the piles are presented below, together withdiscussions of knee braces and grade beams. Grade beams

are horizontal members connecting the piles in both directionsat ground surface, and are recommended in all situations, thatis, with and without truss or knee bracing.

B.1 KNEE BRACING

Knee braces provide adequate bracing when thedifference between pile height and maximum unbraced pile(from Tables A-4 or A-4.1) is 4 feet or less. For such conditionsthe full cross-bracing obtained from a truss is not required, andknee braces can impart the necessary rigidity to the elevatedstructure. They should used for at least the first row of pilessupporting a breakaway wall, to assist in transmitting loads tothe floor and other piles.

Knee braces are relatively short members. They may be2-by-8 lumber or larger and are bolted to the sides of the pilewith two 5/8-inch bolts (minimum) at each ion. In some casesthe builder may prefer to fit the ace under the floor beamframing directly into, or against the pile. In this case, a 4-by-4or larger brace is connected to the pile by one 5/8-inch(minimum) lag screw. Knee braces should be sloped aboutone horizontal to one vertical.

B.2 TRUSS BRACING

In cases where a truss bracing system is needed,indicated by Tables A-4 and A-4.l, the diagonals, struts, andconnections are designed as follows.

B.2.1 Diagonals

Dimension lumber or steel threadbars may be used fordiagonals, depending on the forces acting on the diagonals. For practicality and balanced designs, dimension lumberequivalent to Number 2 Southern Pine in

B-2 Coastal Construction Manual

Figure B-1. Truss normal to beach.

strength, consisting of 2-by-8 or 3-by-8 members, isrecommended for the diagonals. These diagonals may consistof one member or two members for a given direction of loading.When two members are required to form a diagonal, they areplaced on either side of the pile, since the connections havebeen designed for double shear in these cases. The maximumallowable tensile load in double 3-by-8 lumber diagonals is15,000 pounds and 13,000 pounds, for A/B ratios ofapproximately 1.4 and 1.0, respectively. For tensile loadsgreater than these, DYWIDAG (Dyckerhoff and Widmann,Inc., 529 Fifth Avenue, New York, N.Y., 10017) threadbarsare recommended. The wood members and connectionsrequired to resist such loads would be cumbersome.

B.2.1.1 Lumber Diagonals. The allowable loads for singlemember diagonals are given in Tables B-3 for 2-by-8 and B-4for 3-by-8 members and various connection details, asillustrated in Figures B-2 and B-3. In order to determineallowable loads for double member diagonals, the loads inTables B-3 and B-4 should be doubled. The smallestallowable load given for a particular connection/membercombination governs the design.

For example, for a 2-by-8 single diagonal without "A"bolts at the exterior pile connection, the allowable design loadon the member as a result of the pile connection is 4,100pounds, even though the allowable load at the

Bracing B-3

exterior pile connection, in the case of an A/B ratio of 1.0, is5,500 pounds and the allowable load at the interior pileconnection (splice in diagonal) is 5,700 pounds.

The allowable design load for this case could beincreased to 5,500 pounds by adding one 7/8-inch-diameter"A" bolt to the exterior pile connection. The apparent significantimbalance in allowable member and connection loads for thecase without "A" bolts at the exterior pile connection is justifiedto simplify the design for a seemingly infinite number of designconditions. For the case in point, changing the "B" bolts from11/4 inches to 1 inch in diameter results in a decrease of theallowable exterior connection load to 4,200 pounds and anincrease of the allowable diagonal member load to 4,500pounds, thereby resulting in approximately the same allowabledesign load. Therefore, the use of 1-1/4-inch-diameter bolts forthis condition is less than optimum, but justifiable whensimplifying the design to satisfy a large number of designconditions.

Note that 1-inch-diameter "B" bolts would be insufficientto develop the 5,500 pounds if one "A" bolt were used.Therefore, the use of galvanized 1 1/4-inchdiameter and 7/8-inch-diameter bolts is recommended for all lumber connectiondetails where "B" bolts and "A" bolts are specified, respectively.

Side plates to be used with diagonal members, as shownin Figures B-2 and B-3, are to consist of galvanized steel plateshaving a yield strength of 36 kips per square inch, orequivalent plates as available from standard suppliers oftimber connectors. The minimum thickness for galvanizedplates is 1/4 inch for both exterior and interior pile connections.The corresponding minimum plate widths

Figure B-2. Exterior diagonal to pile connection.


Figure B-3. Interior diagonal to pile connection.

are 7 inches for exterior and 2/2 inches for interior ions. Thesewidths should be increased by 1 inches with sheared edges.

Plate end distances, as measured from the center of thehole nearest the plate end, should be a minimum of 7 inchesfor exterior pile connections for the end adjacent to the “B”bolts. For plate ends adjacent to the "A" bolts, the minimumrecommended end distance is 11/2 inches. At interior pileconnections (diagonal splices), the first bolt should be at least6 inches from the end of the lumber. Side plates at interiorconnections should be sized to allow for a 1-inch spacebetween the two ends of the adjoining lumber diagonals.

Bolts at exterior pile connections should be of adequatelength to accommodate the single or double diagonals, steelplates, and nuts. Note that the end of each member is fittedwith one steel side plate on each side of member. At interiorjoints, the length of the bolt to be increased to accommodatethe diagonal members required for stability when loads areapplied from the opposing direction; that is, each leg of thetruss will contain a cross brace. Crossing diagonals are to bebolted at their center crossing points, as shown in Figure B-3.Efforts should be made to connect diagonals to piles within onediagonal member depth below the strut, to avoid excessivejoint eccentricities.

B.2.1.2 Threadbar Diagonals. DYWIDAG threadbars can beused to resist diagonal tensile loads greater than thosepermitted for 3-by -8 lumber members. The use of these barsrather than conventional threaded bars is suggested becauseof the large thread rolled on the threadbars. These largethreads are expected to weather the environment much betterthan fine machine threads, which is important for load-carryingcapacity as well as for retensioning the bars. The threadbarsand fittings, which

Bracing B-5

are readily available, are made of high strength steel (ASTMA722-75) and mild steel (ASTM A615-75).

DYWIDAG representatives can assist in determining theproper threadbar size and the hardware required for a specificapplication. A diagonal consisting of one #7 threadbar (7/8-inch-diameter, Grade 60 steel) has a yield strength of 36,000pounds and is sufficient to resist the largest tensile loadsresulting in diagonals from the maximum applied combinedhorizontal load in Table B-2. These components should beprotected from corrosion by a coating of suitable paint orequivalent. A routine maintenance program to inspect andmaintain these members and fittings should be followed.Alternatively, a suitable factor of safety could be provided in thethreadbars and fittings to permit a reduced cross sectional areaattributable to corrosion. A factor of safety of at least 1.5 isrecommended for threadbars resisting loads in excess of 13,000 pounds. Fittings should be lubricated to permittensioning as required.

Threadbars should be secured to piles using a baseplate, wedge washer, and hex nut (Figure B-4). Thethreadbars should pass through the center of the pile in holeshaving diameters approximately 1/8 to 1/4 inch larger than themaximum diameter of the threadbar, to permit alignment of thebars. Threadbars should be secured to the piles as close tothe pile-to-strut or pile-to-grade beam joint as possible withoutinterfering with the horizontal members. It is important tominimize the eccentricity of these connections at interior pileswhile keeping the plane of the cross bracing near the center ofthe truss. Details of exterior and interior pile joints withinDYWIDAG diagonals are shown in Figure B-4.

B.2.2 Struts

The compressive load resulting on the struts from thecombined horizontal load per pile is shown in Table B-2.

Figure B-4. DYWIDAG threadbar diagonal connections.


Timber sizes to resist the compressive loads shown in Table B-2 are given in Table B-S. Timbers range in size from 4-by -4 to8-by-8, and are assumed to consist of Number 2 Southern Pineor equivalent strength wood.

The struts in the truss system should be cut to fit snuglybetween piles. Wood shims can take up any space left open. They should be connected with galvanized timber connectors(hangers), such as those available from TECO or Simpson.Struts, 4-by-4 up to 4-by-8 in size, can be connected by nailingthrough the connectors. When 6-by-6 or 8-by-8 struts arerequired, use 1/4-inch-thick angles top and bottom of the strutwith eight 3/4-inch lag bolts, four into the strut and four into thepile (see the

marketing literature from manufacturers of timber connectors).

B.3 GRADE BEAMS

In all cases, piles should be braced at the ground line byeither a wood grade beam, a reinforced concrete grade beam,or a concrete slab deepened and well reinforced at the edges.These at-grade supports should be attached firmly to the pile toprovide support even if earth is scoured from beneath thegrade beam/slab.

If wood grade beams are used, the members andconnections should be identical to the members andconnections selected for the struts.

Bracing B-7

TABLE B-1

HORIZONTAL WATER LOADS PER PILE (POUNDS) IN 80 MPH WINDS

PILE 8-INCH TIP PILESHEIGHT 8x8 10x10 WITH EMBEDMENTS OF(FEET) PILES PILES 10 FT 20 FT 30 FT

10.0 2164 2645 1538 1683 182710.5 2343 2869 1659 1817 197511.0 2531 3104 1786 1958 213011.5 2726 3348 1918 2104 229112.0 2929 3602 2055 2256 245812.5 3140 3865 2197 2415 263213.0 3359 4139 2345 2579 281313.5 3586 4423 2498 2749 300014.0 3821 4716 2657 2925 319414.5 4064 5020 2821 3107 339415.0 4314 5333 2990 3295 360115.5 4573 5657 3164 3489 381516.0 4840 5990 3344 3689 403416.5 5114 6333 3530 3895 426117.0 5396 6686 3720 4107 449417.5 5687 7049 3916 4325 473318.0 5985 7421 4117 4548 497918.5 6291 7804 4324 4778 523219.0 6605 8197 4536 5013 549119.5 6927 8599 4753 5255 575720.0 7257 9011 4976 5502 602920.5 7595 9434 5204 5756 630721.0 7940 9866 5437 6015 659321.5 8294 10308 5676 6280 688422.0 8656 10760 5920 6551 7183

NOTE: WATER LOADS INCLUDE WAVE FORCES, CURRENT DRAG FORCES, AND IMPACT FORCES OF 300-POUND DEBRIS.


TABLE B-1 CONTINUED



10.0 2192 2675 1564 1709 185410.5 2372 2900 1685 1844 200211.0 2560 3135 1812 1985 215711.5 2755 3379 1944 2131 231912.0 2959 3634 2081 2284 248612.5 3170 3898 2224 2443 266113.0 3390 4172 2372 2607 284213.5 3617 4457 2526 2778 302914.0 3852 4751 2685 2954 322414.5 4095 5054 2849 3136 342415.0 4347 5368 3018 3325 363115.5 4605 5692 3193 3519 384516.0 4872 6026 3373 3719 406516.5 5147 6369 3559 3925 429217.0 5430 6723 3750 4137 452517.5 5721 7086 3946 4355 476518.0 6019 7459 4147 4579 501118.5 6326 7842 4354 4809 526419.0 6640 8235 4566 5045 552419.5 6963 8638 4784 5287 579020.0 7293 9051 5007 5534 606220.5 7631 9474 5235 5788 634121.0 7977 9907 5469 6048 662721.5 8331 10349 5708 6313 691922.0 8693 10802 5952 6585 7217


Bracing B-9

TABLE B-1 CONTINUED



10.0 2275 2763 1639 1786 193310.5 2456 2990 1762 1922 208211.0 2644 3226 1889 2063 223811.5 2841 3471 2022 2211 240012.0 3046 3727 2160 2364 256912.5 3258 3993 2303 2524 274413.0 3479 4269 2452 2689 292613.5 3707 4554 2606 2861 311514.0 3944 4850 2766 3038 331014.5 4188 5155 2931 3221 351115.0 4440 5470 3101 3410 371915.5 4700 5795 3277 3605 393416.0 4968 6130 3458 3806 415516.5 5244 6475 3644 4013 438217.0 5528 6830 3835 4226 461717.5 5820 7195 4032 4445 485718.0 6119 7569 4235 4670 510518.5 6427 7954 4442 4900 535819.0 6742 8348 4655 5137 561919.5 7066 8752 4874 5379 588520.0 7397 9167 5097 5628 615920.5 7737 9591 5326 5882 643921.0 8084 10025 5561 6143 672521.5 8439 10469 5800 6409 701822.0 8802 10922 6045 6681 7318



TABLE B-1 CONTINUED



10.0 2366 2861 1723 1871 202010.5 2548 3088 1846 2008 217011.0 2738 3326 1974 2150 232711.5 2936 3573 2108 2299 249012.0 3142 3831 2247 2453 266012.5 3356 4098 2391 2614 283613.0 3577 4375 2541 2780 301913.5 3807 4662 2696 2952 320914.0 4045 4959 2856 3130 340514.5 4290 5266 3022 3314 360715.0 4543 5582 3193 3504 381615.5 4805 5909 3369 3700 403216.0 5074 6246 3551 3902 425416.5 5351 6592 3738 4110 448217.0 5636 6948 3930 4324 471817.5 5929 7315 4128 4544 495918.0 6230 7691 4331 4769 520818.5 6539 8077 4540 5001 546219.0 6855 8473 4753 5238 572419.5 7180 8878 4972 5482 599120.0 7513 9294 5197 5731 626620.5 7853 9720 5427 5987 654721.0 8202 10155 5662 6248 683421.5 8558 10601 5902 6515 712822.0 8922 11056 6148 6788 7429


Bracing B-11

TABLE B-1 CONTINUED



10.0 2466 2967 1814 1965 211510.5 2650 3197 1938 2102 226711.0 2841 3436 2067 2246 242411.5 3040 3685 2202 2395 258912.0 3247 3944 2342 2551 276012.5 3462 4213 2487 2712 293713.0 3685 4492 2637 2879 312113.5 3916 4780 2793 3052 331214.0 4155 5079 2955 3232 350914.5 4402 5387 3121 3417 371215.0 4657 5706 3293 3608 392215.5 4919 6034 3470 3805 413916.0 5190 6372 3653 4008 436216.5 5468 6720 3841 4216 459217.0 5755 7078 4034 4431 482817.5 6049 7446 4233 4652 507118.0 6351 7824 4437 4879 532018.5 6661 8211 4646 5111 557619.0 6979 8609 4861 5350 583919.5 7305 9016 5081 5594 610820.0 7639 9434 5306 5845 638320.5 7981 9861 5537 6101 666521.0 8331 10298 5773 6363 695421.5 8688 10745 6014 6631 724922.0 9054 11202 6261 6906 7550



TABLE B-1 CONTINUED



10.0 2575 3083 1914 2066 221910.5 2760 3314 2039 2205 237111.0 2952 3555 2169 2350 253011.5 3153 3806 2304 2500 269612.0 3362 4067 2445 2657 286812.5 3578 4338 2591 2819 304713.0 3803 4618 2743 2987 323213.5 4035 4909 2899 3162 342414.0 4275 5209 3062 3342 362214.5 4524 5519 3229 3528 382715.0 4780 5839 3402 3720 403815.5 5044 6170 3580 3918 425616.0 5316 6509 3764 4122 448016.5 5596 6859 3953 4332 471117.0 5883 7219 4147 4548 494917.5 6179 7589 4347 4770 519218.0 6483 7968 4552 4997 544318.5 6794 8358 4762 5231 570019.0 7114 8757 4978 5471 596419.5 7441 9166 5199 5716 623420.0 7777 9585 5425 5968 651020.5 8120 10015 5657 6225 679421.0 8471 10453 5894 6488 708321.5 8830 10902 6136 6758 738022.0 9197 11361 6384 7033 7682


Bracing B-13

TABLE B-1 CONTINUED



10.0 2692 3208 2021 2176 233110.5 2879 3441 2147 2316 248511.0 3073 3684 2278 2462 264511.5 3275 3937 2415 2613 281212.0 3485 4200 2556 2771 298512.5 3703 4472 2704 2934 316513.0 3929 4755 2856 3104 335213.5 4163 5047 3014 3279 354514.0 4405 5350 3177 3461 374414.5 4655 5662 3346 3648 395015.0 4913 5984 3520 3841 416315.5 5178 6316 3699 4041 438216.0 5452 6658 3884 4246 460716.5 5733 7010 4074 4457 484017.0 6023 7371 4269 4674 507817.5 6320 7743 4470 4897 532418.0 6625 8124 4676 5126 557518.5 6938 8516 4887 5360 583419.0 7259 8917 5104 5601 609919.5 7588 9328 5326 5848 637020.0 7925 9749 5553 6101 664820.5 8270 10180 5786 6359 693221.0 8622 10621 6024 6624 722321.5 8983 11072 6268 6894 752122.0 9352 11533 6516 7171 7825



TABLE B-2

LOADS ON TRANSVERSE TRUSS MEMBERS (POUNDS)

COMBINED A/B RATIO FOR DIAGONAL MEMBERSHORIZONTAL STRUTS

LOAD 1.0 1.1 1.2 1.3 1.4 1.5

1000 1500 2121 2230 2343 2460 2581 27041500 2250 3182 3345 3515 3690 3871 40562000 3000 4243 4460 4686 4920 5161 54082500 3750 5303 5575 5858 6150 6452 67603000 4500 6364 6690 7029 7381 7742 81123500 5250 7425 7805 8201 8611 9032 94654000 6000 8485 8920 9372 9841 10323 108174500 6750 9546 10035 10544 11071 11613 121695000 7500 10607 11150 11715 12301 12903 135215500 8250 11667 12265 12887 13531 14194 148736000 9000 12728 13379 14058 14761 15484 162256500 9750 13789 14494 15230 15991 16775 175777000 10500 14849 15609 16402 17221 18065 189297500 11250 15910 16724 17573 18451 19355 202818000 12000 16971 17839 18745 19681 20646 216338500 12750 18031 18954 19916 20912 21936 229859000 13500 19092 20069 21088 22142 23226 243379500 14250 20153 21184 22259 23372 24517 25690

10000 15000 21213 22299 23431 24602 25807 2704210500 15750 22274 23414 24602 25832 27097 2839411000 16500 23335 24529 25774 27062 28388 2974611500 17250 24395 25644 26945 28292 29678 3109812000 18000 25456 26759 28117 29522 30968 32450

Bracing B-15

TABLE B-3

ALLOWABLE LOADS FOR SINGLE 2-BY-8 DIAGONALS

Joint at Joint atExterior Interior 2x8 Member

A/B Pile Pile No "A" One "A" Ratio (pounds) (pounds) Bolt Bolt

1.00 6500 5700 4100 5500

1.43 7500 5700 4100 5500

Notes on Tables B-3 and B-4:

I. A and B are defined in Figure B-1; "A" bolts are identifiedin Figure B-2.

2. Two 1 1/4-inch-diameter bolts ("B" bolts) are used toconnect diagonals to piles at exterior joints.

3. Bolts at interior joint consist of 7/8-inch-diameter bolts,installed in a single row along the center of the diagonal.Require three bolts per diagonal, spaced 3 inches apart;require one bolt to connect diagonals to pile. SeeSection B.2.1.1 for edge and end distances.

4, All member ends are reinforced with metal side plateson both sides of member as described in text.

5. Member loads are determined at critical net sectionthrough diagonal connection.

TABLE B-4

ALLOWABLE LOADS FOR SINGLE 3-BY-8 DIAGONALS

Exterior Interior 3x8 Member A/B Joint Joint No "A" One "A" Ratio (pounds) (pounds) Bolt Bolt

1.00 6500 10000 6700 9000

1.43 7500 10000 6700 9000

TABLE B-5

ALLOWABLE STRUT LOADS

Allowable Strut Load (pounds) Size

3000 4x44800 4x66300 4x8

16000 6x616000 8x8

C-1Appendix C

DESIGN WORKSHEETS

PILE DESIGN WORKSHEET1 of 4


Width ______ feet

Length ______ feet

Number of Stories ______

Type of Soil ______________

Clearance Above Grade ______ feet

Design Wind Speed ______ miles per hour

Number of Piles Required (Figure A-I)

Along Width ______ or ______

Along Length ______ or ______

Combination (Width/Length) ___/___ or ___/___ or ___/___ or ___/___

Total Number (Width x Length) ______ or ______ or ______ or ______

Downward Load Per Pile (Table A-1) ______ or ______ or ______ or ______ pounds


8x8 Square Pile ______ or ______ or ______ or ______ feet


8-inch Tip Round Pile ______ or ______ or ______ or ______ feet

Horizontal Wind Load Per Pile (Table A-2) ______ or ______ or ______ or ______ pounds

PILE DESIGN WORKSHEET (CONTINUED)2 of 4






8x8 Square Pile ______ ______ ______ ______

10x10 Square Pile ______ ______ ______ ______

8-inch Tip Round Pile ______ ______ ______ ______

Information on Enclosure Below BFE

Width x Length ___X___ or ___X___ or___X___ or ___X___ feet

Piles/Spacing Along Width ___/___ or ___/___ or ___/___ or ___/___

Piles/Spacing Along Length ___/___ or ___/___ or ___/___ or ___/___

No. of Piles in Enclosure ______ ______ ______ ______

No. of Piles Carrying Load ______ ______ ______ ______


Wall Height ______ feet

PILE DESIGN WORKSHEET (CONTINUED)3 of 4

Load Resistance of Breakaway Walls

Selected Fastener Size ______

No. Fasteners per Loaded Panel ______ or ______ or ______ or ______

(Table A-11)

Ultimate Capacity per Fastener ______ pounds

(Table A-10)

Panel Ultimate Capacity ______ or ______ or ______ or ______ pounds


Total Breakaway Wall Capacity ______ or ______ or ______ or ______ pounds (Panel Ultimate Capacity ÷ No. Loaded Panels)

Horizontal Load per Pile at Breakaway ______ or ______ or ______ or ______ pounds Wall Collapse (Total Wall Capacity ÷ No. of Piles Carrying Load)

Horizontal Load on Top Fasteners ______ or ______ or ______ or ______ pounds

(Horizontal Load ÷ 2)

Combined Horizontal Load per Pile ______ or ______ or ______ or ______ pounds (Wind + Top Fastener Loads)

Maximum Unbraced Height of Pile (Table A - 4.1) (Enclosure below BFE)




PILE DESIGN WORKSHEET (CONTINUED)

4 of 4

Is Bracing Required? (Does clearance above grade exceed maximum unbraced pile height?) (Enclosure Below BFE)

8x8 Square Pile ______ ______ ______ ______

10x10 Square Pile ______ ______ ______ ______

8-inch Tip Round Pile ______ ______ ______ ______


Along Width ______

Along Length ______

Total Number (Width x Length) ______

Size of Pile ______

Pile Embedment Depth ______ feet

Is Bracing Required? ______ (if yes, see 'Bracing Design Worksheet')

CONNECTION DESIGN WORKSHEET1 of 2

General House Information

Width ______ feet

Length ______ feet



Connections Between Floors Uplift Loads per Foot of Wall (Table A-5)

Roof Connection ______ pounds per foot

Second Floor Connection ______ pounds per foot

First Floor Connection ______ pounds per foot

Connectors Selected Based on Manufacturers' Data

Type ____________

Spacing ______ inches

CONNECTION DESIGN WORKSHEET (CONTINUED)2 of 2

Floor Beam Connection

Number of Piles Required (Figure A-1) ___/___ or ___/___ or ___/___ or ___/___

Combination (Width/Length)

Downward Load per Pile (Table A-1)

100% of Load ______ or ______ or ______ or ______ pounds

50% of Load ______ or ______ or ______ or ______ pounds

Uplift Load per Pile (Table A-6) ______ or ______ or ______ or ______ pounds

Capacity per Bolt of Selected Floor Beam Connection (Table A-7) ______ pounds

Type of Connection ____________

Beam

Bolt Diameter ______ inches

Number of Bolts ______

Pile

Bolt Diameter ______ inches

Number of Bolts ______

BRACING DESIGN WORKSHEET1 of 3


Width ______ feet

Length ______ feet


Clearance Above Grade ______ feet



Combination (Width/Length) ___/___ or ___/___ or ___/___ or ___/___

Maximum Unbraced Height of Pile (Table A-4)




Can Knee Braces Be Used? (Is clearance above grade minus maximum unbraced height 4 feet or less?)

8x8 Square Pile ______ or ______ or ______ or ______

10x10 Square Pile ______ or ______ or ______ or ______

8-inch Tip Round Pile ______ or ______ or ______ or ______

If Knee Bracing Cannot Be Used, Continue on for Truss Bracing

BRACING DESIGN WORKSHEET (CONTINUED)2 of 3

Horizontal Water Loads per Pile (Table B-1)

8x8 Square Pile ______ pounds

10x 10 Square Pile ______ pounds

8-inch Tip Round Pile ______ pounds

Horizontal Wind Loads per Pile (Table A-2) ______ or ______ or ______ or ______ pounds

Combined Horizontal Loads per Pile (Wind + Water)

8x8 Square Pile ______ or ______ or ______ or ______ pounds


8-inch Tip Round Pile ______ or ______ or ______ or ______ poundsTruss Width = B = Pile Spacing Along Length ______ or ______ or ______ or ______ feet

A/B Ratio for Diagonal Members (Figure B-1) ______ or ______ or ______ or ______

Loads on Transverse Members (Table B-2)

Struts



8-inch Tip Round Pile ______ or ______ or ______ or ______ pounds

Diagonals



8-inch Tip Round Pile ______ or ______ or ______ or ______ pounds

BRACING DESIGN WORKSHEET (CONTINUED)3 of 3

Information on Bracing to be Used for Selected Pile Combination

Strut Size (Table B-5) ______

Diagonals (Tables B-3 and B-4)

Single or Double ______

Size ______

"A" Bolt (yes/no) ______

Design Equations and Procedures D-1

Appendix D

DESIGN EQUATIONS ANDPROCEDURES

The engineering procedures and equations used todevelop the design tables in Appendices A and B arepresented in this appendix. Use of these procedures allows adesigner to develop and evaluate individual designs whichmay not be encompassed by the typical designs addressed bythe tables.

For ease of organization, the design procedures hereinare presented in the order of and referenced to the designtables. In general, each supporting equation is presenteddescriptively, then with variable names and

actual values that were used to produce the tables. With theassumptions clearly stated, a designer can readily substitutealternative assumptions and values in order to evaluate aspecific design.

Variable names used in the equations generallycorrespond directly to those used in the computer programs(Appendix E) for the design tables. A few names have beenchanged slightly for clarity in presentation of the equations.

D-2 Coastal Construction Manual

D.1 PROCEDURE A-1: DOWNWARD LOADS PER PILE

This procedure calculates downward loads per pile resulting from dead and frequently applied (non-storm) live loads. Thebuilding is assumed to have 2-foot eaves.

Roof + attic load = (plan area) (unit dead + live pressures)DATTIC = (width + 4) (length + 4) (44 psf)

Second floor load = (plan area) (unit pressure)D2ND = (width) (Length) (38.5 psf)

First floor load = (plan area) (unit pressure)DIST = (width) (length) (48.5 psf)

Total vertical load = VLOAD = DATTIC + D2ND + DIST

Load per pile = (total vertical load) (number of piles)VPlLE = VLOAD/(NPW x NPD)

Note: For one-story buildings, D2ND = 0.


D.2 PROCEDURE A-2: HORIZONTAL WIND LOADS PER PILE

This procedure evaluates total horizontal wind load on the building, resolved into a horizontal load applied to the top of eachpile. The building is assumed to have 9-foot stories; the roof ridge is parallel to the wind, sloped 3:1, with 2-foot eaves.

QH = Horizontal wind pressure on story being considered, for design wind velocity from building code (psf)W = Building width perpendicular to wind direction (ft)

Horizontal Force on attic = (vertical surface area) (wind pressure)HATTlC = (W2/12) (QH)

Horizontal Force on 2nd story H2ND = (W x 9) (QH)

Horizontal force on 1st story = HIST = (W x 9) (QH)

Total horizontal load = HLOAD = HATTIC + H2ND + HIST

Horizontal load per pile = (total load) (number of piles)NPILE = HLOAD/(NPW x NPD)

Note: For the total horizontal load on a one-story building, omit H2ND and revise wind pressures for reduced building height.


D.3 PROCEDURE A-3: MINIMUM EMBEDMENT DEPTH OF PILES

This procedure calculates the minimum embedment depth of a pile required to safely carry a given vertical load. Soil typesconsidered are sand and clay. Pile types considered are 8-and 10-inch square and 8-inch tip round tapered.

S = surface area per unit length of pile= 10 inches x 4/12 inches per foot = 10/3 square feet for 10-inch square pile= 8 inches x 4/12 inches per foot = 8/3 square feet for 8-inch square pile

π(D+TH) = π (8/12 + TH) for 8-inch tip round tapered pileT = increase in radius per length of tapered pile = typically 0.5 inch/10 feet = 1/240K = lateral earth pressure coefficientγ = buoyant unit weight of sand (pcf)δ = friction angle between wood and soil (degrees)FS = factor of safetyH = embedment depth of pile (feet)P = allowable vertical load on pile (pounds)Cl = clay adhesion to wood (psf)

D.3.1 Square Piles

D.3.1.1 Square Piles in Sand. Bearing capacity, P, in sand is calculated as

P = frictional capacity + tip capacity

= 1/2 γ H2 K tan δ x S/FS + 1/2 γ HNqA/FS

Solve for H in quadratic equation:

(1/2γ KS tan δ /FS)H2+(1/2 γHNqA/FS)H-P=0 (1)

For loose sand, choosing typical soil parameters γ = 50 pcf, K = 0.6, δ = 20°, Nq = 33, equation (1) becomes:

(1/2 x 50 x 0.6 x S tan 20/FS) H2 + (1/2 x 50 x 33 x A/FS) H - P = 0


Substituting values for S and A corresponding to pile size and letting FS = 2.5

(1/2 x 50 x 0.6 x 8/3 x tan 20/2.5) H2 + (1/2 x 50 x 33 x 0.44/2.5) H - P = 0 for 8-inch piles

and


For medium dense sand, choosing typical parameters γ = 65 pcf, K = 0.9, δ = 23°, Nq = 65, equation (1) becomes:

(1/2 x 65 x 0.9 x S tan 23/FS) H2 + (1/2 x 65 x 65 x A/FS) H - P = 0

Substituting values for S and A corresponding to pile size, with FS = 2.5


and



D.3.1.2 Square Piles in Clay. Bearing capacity P in clay is calculated as

P = adhesion capacity + tip capacity

= S x H x Cl/FS + Cl x Nc x A/FS

where soil cohesion approximately equals soil-pile adhesion.

H= ( P x FS) - (Cl x N c x A ) (2)S x Cl

For soft clay, choosing typical values Cl = 250 pcf and Nc = 9, and letting FS = 2, equation (2) becomes:

H = 2P - (250 x 9 x 0.44 ) for 8-inch piles in soft clay8/3 x 250

H= 2P - (250 x 9 x 0.69 ) for 10-inch piles in soft clay10/3x250

For medium stiff clay, choosing typical values Cl = 450 pcf and Nc = 9, with FS = 2, equation (2) becomes:

H = 2P - (450 x 9 x 0.44 ) for 8-inch piles in medium stiff clay8/3 x 450

H= 2P - (450 x 9 x 0.69 ) for 10-inch piles in medium stiff clay10/3x450


D.3.2 Round Tapered Piles

D.3.2.1 Round Piles in Sand. Bearing capacity is calculated as

P = frictional capacity + tip capacity

= 1/2 γ H2 K tan δ x S/FS+1/2 γ HNq A/FS

= 1/2 γ H2 K tan δ x π(D + TH)/FS + 1/2 γ HNqA/FS

= T π γ K tan δ H3 + D π γ K tan δ H2 + γ NqA H2 x FS 2 x FS 2 x FS

Solve for H in cubic equation:

T π γ K tan δ H3 + D π γ K tan δ H2 + γ NqA H - P = 0

2 x FS 2 x FS 2 x FS (3)

For loose sand, choosing typical soil parameters γ= 50 pcf, K = 0.6, δ 20°, Nq = 33, equation (3) becomes:

T π x 50 x 0.6 tan 20 H3 + D π x 50 x 0.6 tan 20 H2 + 50 x 33A H - P = 02 x FS 2 x FS 2 x FS

Substituting pile taper T = 1/240, tip diameter D = 8 inches, tip area A = 0.35 square feet, and FS = 2.5:

1/240 x π x 50 x 0.6 tan 20 H3 + 0.33 π x 50 x 0.6 tan 20 H2 + 50x33x0.35 H - P = 0 for 8-inch tip piles5 5 5

For medium dense sand, choosing typical values = 65 pcf, K = 0.9, = 23o, Nq = 65, equation (3) becomes:

T π x 65 x 0.9 tan 23 H3 + D π x 65 x 0.9 tan 23 H2 + 65 x 65A H - P = 02 x FS 2 x FS 2 x FS

Substituting the selected pile characteristics and letting FS = 2.5:

1/240 x π x 65 x 0.9 tan 23 H3 + 0.33 π x 65 x 0.9 tan 23 H2 + 65 x 65 x 0.35 H - P = 0 for 8-inch tip piles5 5 5


D.3.2.2 Round Piles in Clay. Bearing capacity is calculated asP = adhesion capacity + tip capacity

= (S x H x Cl/FS) + (Cl x Nc X A/FS)

= π (D + TH) x H x Cl/FS + Cl x Nc x A/FS

where soil cohesion approximately equals soil-pile adhesion.

Solve for H in quadratic equation: π T Cl H2 + π D Cl H + Nc A x Cl - P = 0 (4)

FS FS FS

For soft clay, choosing typical soil parameters Cl = 250 pcf and Nc = 9 and with FS = 2, equation (4) becomes:

π T x 250 H2 + π D x 250 H+ 9A x 250 - P = 02 2 2

Substituting T = 1/240, D = 8 inches, and A = 0.35 square feet:

π /240 x 250 H2 + 0.67 π x 250 H + 9 x 0.35 x 250 - P = 0 for 8-inch tip piles2 2 2

For medium stiff clay, choosing typical Cl = 450 pcf, equation (4) becomes:

1240x 450 H2 + 0.67 x 450 H+ 9 x 0.35 x 450 - P = 0 for 8-inch tip piles2 2 2

Notes for all piles:1. Minimum 10-foot embedment is recommended for all piles.

2. These are the embedment depths required for adequate support of vertical loads. It is essential to provide additionalembedment in erosion-prone areas. Depth of potential scour should be researched locally; if no local information is available,assume 4 feet of scour in sand and add to above embedments for first row of houses from shore. For inland houses assume 2feet of scour in sand and add to above embedments.

3. Required embedment to resist lateral loads was also evaluated. For the assumed soil types and minimum 10-footembedment, vertical capacity as calculated above was determined to be the governing criterion for embedment.


D.4 PROCEDURE A.4: MAXIMUM UNBRACED HEIGHT OF PILES

This procedure calculates maximum unbraced height of a pile by equating allowable bending moment in the pile to momentgenerated by water and debris forces on the pile and wind forces on the building.

Fm = wave force on pile (pounds)

Mm = moment of wave force around pile base (foot-pounds)

Fd = current drag force on pile (pounds)

Md = moment of current drag force around pile base (foot-pounds)

F = debris impact force on pile (pounds)

M = moment of debris impact force around pile base (foot-pounds)

LOAD = applied wind load at top of pile (pounds)

Mw = moment of wind force around pile base (foot-pounds)

Mp = allowable bending moment in pile (foot-pounds)

DIA = diameter of pile (inches)

Hw = design water height = minimum pile height above existing grade (feet)

Hp = actual pile height above existing grade (feet)


D.4.1 Moment of Wave Forces

Wave force on a pile is derived in Procedure B-1, yielding

Fm = 14.255 (DIA/12) Hw

2 for round piles

= 23.758 (DIA/12) Hw

2 for square piles

Moment around base of pile (1984 Shore Protection Manual ) is:Mm = (Fm)(1.11d)

where d = Hw /1.546 (see Figure D-1)

Mm =(Fm)(0.178 Hw)

= 10.235 (DIA/12) Hw

3 for round piles

= 17.058 (DIA/12) Hw

3 for square piles


Water depth =

minimum pile height =

HW

wave heightabove stillwater= 0.7 Hb

HW = (BFE) - (ground surface elevation) = d + 0.7 Hb

= Hb + 0.7 Hb 0.78

+ 1.982 Hb

Figure D-1. Water depth relationships.


D.4.2 Moment of Current Drag Forces

Current drag force on a pile is derived in Procedure B-1, yielding:

Fd = CDHW (DIA/12) v2

For wind speed ≤ 80 mph, assume water velocity v = 3 knots = 5.06 ft/sec:

Fd = CDHW (DIA/12) (5.06) 2

Moment arm is 1/2 HW, so moment around base of pile is:

Md = CDHW2 (DIA/24) (5.06) 2

For wind speed > 80 mph, assume v = 5.06 ft/sec in lower 3/4 of water column and v = 0.057 Ws in upper 1/4,

Fd = 3/4 (CDHW) (DIA/12) (5.06) 2 + 1/4 (CDHW) (DIA/12) (0.0587 Ws) 2

Moment arm of lower 3/4 of water column is (3/8) HW, and moment arm of upper 1/4 is (7/8) HW. Thus moment around base ofpile is:

Md = (3/8) (3/4) (CDHW2) (DIA/12) (5.06) 2 + (7/8) (1/4) (CDHW

2) (DIA/12) (0.0587 Ws) 2

= (CDHW2) (DIA/12) (7.201 + 0.000754 Ws

2)

with CD = 1.2 for round, 2.0 for square.

Md = HW2 (DIA/12) (8.641 + 0.000905 Ws

2) for round piles

= HW2 (DIA/12) (1 4.402 + 0.00151 Ws

2) for square piles


D.4.3 Moment of Debris Impact Forces

Debris impact force on a pile is derived in Procedure B-1. For an assumed 300-Ib debris load,

F = 238.6 lb for wind speed ≤ 80 mph

= 0.032 Ws 2 lb for wind speed > 80 mph

Debris is assumed to impact at top of pile at maximum water height, so moment arm around base of pile is equal to pile heightHw:

M = F x HW

= 238.6 HW for wind speed ≤ 80 mph

= 0.032 Ws 2 HW for wind speed > 80 mph

D.4.4 Moment of Wind Forces

Resolution of wind forces on the building into horizontal loads applied to the top of a pile is described in ProcedureA-2. Moment arm around base of pile is equal to pile height Hp, which is equal to or greater than water height Hw.

MW = LOAD x Hp


D.4.5 Allowable Bending Moment of Piles

Allowable bending moment of a pile is expressed as:

Mp = 1.33 σΙ/y

where 1.33 = factor of allowable stress increase for transient loads

σ = allowable tensile stress (psf)

Ι = section modulus (ft4)

Y = distance to section centroid (ft) For round pile:

For round pile:

Ι = π (DIA/12) 4

64

Y = 1/2 (DIA/12)

Assuming σ = 1850 psi = 1850 x 144 psf (disregarding relatively small uplift forces), then

Mp = 1.33(1850 x 144) π ( DIA/ 12) 4 /(DIA/24 )64

= 1.33(1850) π (DIA) 3 384

For square pile:

Ι = (DIA/12) 4

12

Y = 1/2 (DIA/12)

Assuming σ = 1300 psi = 1300 x 144 psf (disregarding uplift forces), then


Mp = 1.33 (1300x 144) (DIA/12) 4 / (DIA/24) 12

= 1.33(1300) (DIA) 3 72

D.4.6 Maximum Unbraced Pile Height

Pile height (= water height HW) is solved by equating allowable bending moment in pile to applied moment around base ofpile.

Mp = Mm + Md + M + MW

0 = Mm + Md + M + MW - Mp

This results in a cubic equation to be solved for pile height.

NOTES:

1. Results presented in Table A-4 are based on the assumption that pile height above grade Hp equals maximum designwater height Hw (at BFE). For cases where Hp > Hw, Hw should be expressed as a fraction of Hp, so the above equationscan be solved for Hp, resulting in a higher allowable unbraced height.

2. If Table A-4 indicates that bracing is required, a designer may reduce some of the conservatism by reducing wave forceFm in above equations by up to 25 percent. This is realistic because the full force of a breaking wave is likely to occuragainst only one row of piles at a time, and will be distributed to other piles by the grade beams and floor frame.


D.5 PROCEDURE A-4.1: MAXIMUM UNBRACED HEIGHT FOR PILES SUPPORTING BREAKAWAY WALLS

This procedure calculates maximum unbraced height of a pile supporting a breakaway wall by equating allowable bendingmoment in a pile to moment generated by wind forces on the superstructure and water and wind forces on the breakaway wall at themoment of breakaway wall collapse.

D.5.1 Moment of Wind Forces on Superstructure

Resolution of wind forces on the building into horizontal loads applied to the top of a pile are described in ProcedureA-2. Moment arm around the base of the pile is equal to pile height Hp:

MW = (wind load per pile) (Hp)

D.5.2 Moment of Breakaway Wall Forces

Calculation of maximum forces on a breakaway wall per pile are described in the Pile Design Worksheet, based on theallowable load range of 10 to 20 psf specified by NFIP. Moment arm around the base of the pile for half of the load (resisted by the topfasteners) is equal to pile height Hp. Moment arm for the half of the load resisted by the bottom fasteners is zero.

Mb = 1/2 (breakaway wall ultimate capacity per pile) (Hp) + 0

D.5.3 Allowable Bending Moment in Piles

The allowable bending moment of a pile, as derived in Procedure A-4, is expressed as:

Mp = 1.33(1850) π (DIA) 3 for round piles 384

= 1.33(1300)(DIA) 3 for square piles 72


D.5.4 Calculation of Maximum Unbraced Pile Height

Pile height Hp is solved for by equating allowable bending moment in a pile to applied moment around the base of the pile.

Mp = MW + Mb

= (Hp) (wind load per pile + 1/2 breakaway wall ultimate capacity per pile)

Solving for Hp:

Hp = 1.33 (1850) π (DIA) 3 /384 (wind load + 1/2 wall capacity) for round piles

= 1.33(1300)(DIA) 3/72 (wind load + 1/2 wall capacity) for square piles


D.6 PROCEDURE A.5: UPLIFT LOADS PER FOOT OF WALL

This procedure produces wind-induced uplift load values per foot of wall at connections between stories of one- and two-storybuildings. The building is assumed to have 9-foot stories; the roof ridge is parallel to the wind, sloped 3:1, with 2-foot eaves.

QH = horizontal wind pressure on story being considered, from building code (psf)

QV = vertical uplift pressure on roof (psf)

QU = vertical uplift pressure on exposed underside of building (psf)

W = building width perpendicular to wind direction (feet)

L = building length parallel to wind direction (feet)

Uplift loads at each connection level are sum of vertical uplift minus dead loads plus uplift resulting from moment due tohorizontal loads.

D.6.1 Rafter Connections

Roof uplift = (roof surface area) (wind uplift pressure)VIROOF = (W + 4) (L + 4) (QV)

Dead load of roof and attic = (plan area) (unit dead load)DATTIC = (W + 4) (L + 4) (14 psf)

Horizontal force on attic = (vertical surface area) (wind pressure)HIATIC - (W2/12) (QH)

Moment due to horizontal force = (force) (moment arm to centroid)MIATIC = (HIATIC) (W/18)


Summation of uplift on rafter connections, along two lengths of house (see Figure D-2):

( roof uplift) - (dead load ) +(vertical surface area) (wind pressure)connected length

NIATIC = VIROOF - DATTIC + MIATIC

2L (2/3)L2

Note: Wind pressures based on ANSI A58.1 - 1982 vary with building height. Therefore, uplift on roof connections differs for one-andtwo-story buildings.

D.6.2 Connections Between StoriesRoof uplift on two-story roof = V2ROOF = (W + 4) (L + 4) (QV)

Dead load of second story = (plan area) (unit dead load)D2ND = (W) (L) (8.5 psf)

Dead load of roof and attic = DATTIC = (W + 4) (L + 4) (14 psf)

Horizontal force on second story = (vertical surface area) (wind pressure)

H2ND = (W x 9) (QH)

Horizontal force on attic = H2ATIC = (W2/12) (QH)

Moment due to total horizontal force above connections = (force) (moment arm)

M2ND = (H2ND x 4.5) (H2ATIC x (W/18 + 9))

Summation of uplift on connections, around full perimeter (see Figure D-3):

roof uplift - total dead load + vertical force resisting applied momentperimeter

K2ND = VIROOF - (DA TTIC + D2ND) + M2ND 2L + 2W L (W + 2L/3)


applied moment = MIATIC = resisting moment = (2) (1/2 FL) (2/3L)

maximum force F = MIATIC/ (2/3L2)

Figure D-2. Resisting force - roof connections.


applied moment = M2ND = resisting moment = (2) (1/2 FL) (FW)(L)

maximum force F = M2ND/ (L)(W = 2/3L)

Figure D-3. Resisting force - story connections.


D.6.3 Bottom Floor Connections (Two-story)

V2ROOF = (W + 4) (L + 4) (QV)

Dead load of 1st story = (plan area) (unit dead load)DIST =(W x L)(8.5psf)

D2ND = W x L (8.5 psf)

DATTIC = (W + 4) (L + 4) (14 psf)

Horizontal force on 1st story = (vertical surface area) (wind pressure)HlST2 = (W x 9) (QH)

H2ND = (W x 9) (QH)

H2ATIC = (W2/12) (QH)

Vertical uplift on exposed underside = (surface area) (wind pressure)VUNDER = (W x L) (QU)

Moment due to total horizontal force = (force) (moment arm)MIST2=(HIST2 x 4.5)+(H2ND x 13.5)+(H2ATIC x (W/18+18))

Summation of uplift on connections, around full perimeter (see Figure D-3):

roof uplift + underside uplift - dead load + vertical force resisting applied momentperimeter

NIST2 = V2ROOF + VUNDER - (DATTIC + D2ND + DIST) + MIST1 2L + 2W L (W + 2L/3)

Note: For bottom floor uplift on a one-story building, omit second story dead loads and horizontal forces, and revise wind pressuresand moment arms.


D.7 PROCEDURE A-6: UPLIFT LOADS PER PILE

This procedure calculates uplift loads per pile resulting from wind forces on the building. The building is assumed to have 9-footstories; roof ridge is parallel to wind, sloped 3:1, with 2-foot eaves.

QH = Horizontal wind pressure on story being considered, for design wind velocity from building code (psf)QV = Vertical uplift pressure on roof (psf)QU = Vertical uplift pressure on exposed underside of building (psf)W = Building width perpendicular to wind direction (feet)L = Building length parallel to wind direction (feet)NPW = Number of piles along building widthN = Number of piles along building lengthFo = Maximum uplift per pile due to moment (pounds)

Uplift loads at top of piles are sum of vertical uplift minus dead loads plus uplift resulting from moment due to horizontal loads.

D.7.1 Forces on Roof and Attic

Vertical uplift on roof = (surface area) (wind pressure)V2ROOF = (W + 4) (L + 4) (QV)

Dead load of roof, attic = (plan area) (unit pressure)DATTIC = (W + 4) (L + 4) (14 psf)

Horizontal force on attic = (vertical surface area) (wind pressure)

H2ATIC = W 2 (QH)

12


D.7.2 Uplift Forces on Second Story

Dead load of second story = (plan area) (unit pressure)D2ND = (W x L) (8.5 psf)

Horizontal force on second story = (vertical surface area) (wind pressure)H2ND = (W x 9) (OH)

D.7.3 Uplift Forces on First Story

Dead load of first story = (plan area) (unit pressure)DIST = (W x L) (8.5 psf)

Horizontal force on first story = (vertical surface area) (wind pressure)HIST2 = (W x 9) (QH)

Vertical uplift on exposed underside of building = (exposed surface area) (wind pressure)VUNDER = (W x L) (QU)

D.7.4 Uplift at Top of Piles Due to Vertical Loads

Total vertical load = roof uplift + underside uplift - dead loadsVLOAD2 = V2ROOF + VUNDER -(DATTIC + D2ND + DIST)

Vertical load per pile = total vertical load/number of pilesVPILE2 = VLOAD2/(NPW + N)


D.7.5 Uplift at Top of Piles Due to Moment

Moment about top of piles = (summation of horizontal forces) (moment arms)MMENT2 = (H2ATIC x (W/18 + 18)) + (H2ND x 13.5) + (HIST2 x 4.5)

For each row of piles parallel to applied wind moment MMENT2, we want to solve for maximum resisting force Fo, whichoccurs at outermost piles. The force in each interior pile is proportional to its distance from centroid (see Figure D-4, a and b).

Total moment on row of piles = summation of (F x moment arm),where moment arm = (spacing) (number of spaces to centroid)

Moment row=2 Fo x 1/2 L (N-1)+2F1 x 1/2 L (N-3)+2F2 x 1/2 L (N-5) +...N-1 N-1 N-1

In terms of Fo, from Figure D-4:

Moment row = Fo x L (N-1) + F o (N-3) L (N-3)+ F o (N-5) L (N-5) +...

N-1 N-1 N-1 N-1 N-1

Total moment MMENT2 = (Moment row) (NPW)

Solving for Fo:

where ( N - x) 2 terms are added in numerator until (N - x) ≤ 0 (N- 1)2


elevation

length L(# piles = N)

plan

Figure 4-a. Applied moment on pile row.

# pile bays along length L = N-1

F 1 = (spacing)(1/2)(#bays - 2) = (N-1)-2

Fo (spacing)(1/2)(#bays) N-1

F 2 = (N-1) -4 etc.

Fo N-1

Figure 4-b. Resisting forces along pile row.


D.7.6 Total Uplift at Top of Piles

Total uplift per pile = (uplift due to vertical loads) + (uplift due to moment)NVMAX2 = VPILE2 + Fo

Note: For one-story buildings, omit D2ND and H2ND, and revise wind pressures and moment arms for reduced height.


D.8 PROCEDURE B-1: HORIZONTAL WATER LOADS PER PILE

This procedure calculates horizontal water loads per pile for varying wind speeds. Maximum water loads includeinertial and drag forces of waves, current drag forces, and impact forces of waterborne storm debris.

Fm = wave force (pounds)

D = pile width or diameter (feet)

DIA = pile width or diameter (inches)

ρ = unit mass of water (lb-sec2/ft)

g = gravitational acceleration (ft/sec2)

Hb = wave height (feet)

HW = total water depth = minimum pile height (feet)

Hp = actual pile height (feet)

Fd = current drag force (pounds)

A = projected area of pile = HW x DIA/12 for square or round (square feet)

Ws = wind speed (mph)


D.8.1 Wave Forces

For shallow water breaking waves, force on round pile (1984 Shore Protection Manual) :

Fm CD x 1/2 ρgD Hb

2

with CD = 1.75 for breaking wave

= (1.75) (1/2) (2) (32.2) (DIA) (Hb

2)

= 56 ( DIA ) Hb

2

12

Expressing Hb in terms of total water depth HW (see Figure D-1):

Fm = 56 (DIA/12) HW /1.982) 2

= 14.255 (DIA/12) HW

2 for round piles

For square piles, multiply by ratio of current drag coefficients (2.0 square/1.2 round):

Fm = 14.255 (2.01/1.2)(DIA/12) HW

2

= 23.758 (DIA/12) HW

2 for square piles


D.8.2 Current Drag Forces

Drag force due to currents (1984 Shore Protection Manual) :

Fd = 1/2 CDAv2

For wind velocity of 80 mph or less, assume water column velocity = 3 knots = 5.06 ft/sec.

Fd = (1/2) (2) CD HW (DIA/12) (5.06) 2

with CD = 2.0 for square piles

= 1.2 for round piles

For wind velocity greater than 80 mph, assume water velocity of lower 3/4 of water column is 5.06 ft/sec. Assume water velocityin upper 1/4 of water column is affected by wind shear and is equal to 4 percent of wind speed Ws.

V 3/4 = 5.06

V 1/4 =0.04 x Ws mph x 88ft/sec = 0.0587 Ws60 mph

Fd 3/4 = 3/4 (1/2 x 2 x CD x HW x (DIA/12) x 5.062)

= 3/48 x CD x HW x DIA x (5.06) 2

Fd 1/4 = 1/4 (1/2 x 2 x CD x HW x (DIA/12) x (0.0587 Ws) 2)

= 1/48 (CDHW) (DIA) (0.0587 Ws) 2

Total Fd = Fd 3/4 + Fd 1/4

= 1/48 x CD x HW x DIA (3 x (5.06) 2 + (0.0587 Ws)

2)

with CD = 2.0 for square piles

= 1.2 for round piles


D.8.3 Debris Impact Forces

Using basic relations of deflection, velocity, and acceleration:

Deflection S = 1/2 at2 and a = v/t

So, S = 1/2 (v/t)t2

t = 2S/v

Impact force F = m dv dt

= m v/(2S/v)

If we consider a 300-pound debris load, moving with the velocity of the water surface for various wind speeds, and anallowable pile deflection of 0.5 feet,

F = 300 v 32.2 (l/v)

= 9.32 v2

= 9.32 (5.06) 2 = 238.6 lb for wind speed ≤ 80 mph

= 9.32 (0.0587 Ws) 2 = 0.032 Ws

2 lb for wind speed > 80 mph

D.8.4 Total Forces on Piles

Maximum water loads per pile = wave forces + current forces + debris impact forces

= Fm + Fd + F


D.9 PROCEDURE B-2: LOADS TRANSFERRED TO FOUNDATION TRUSS MEMBERS

This procedure evaluates loads imparted to horizontal and diagonal bracing members resulting from longitudinally appliedhorizontal loads (applied parallel to truss).

Horizontal strut load = 1.5 (applied horizontal load)STRUT = 1.5 (load)

Diagonal load = (strut load) diagonal length strut length

DIAG = STRUT x

Computer Program Listings E-1

Appendix E

COMPUTER PROGRAM LISTINGS

E-2 Coastal Construction Manual

Construction Cost F-1

Appendix F

CONSTRUCTION COST

A variety of construction methods, as presented in thismanual, exist for elevating residential structures in coastal highhazard areas, and for reducing wind and water damage tothese houses in severe storms. Implementation of theseconstruction methods, however, can be expected to increasethe cost of the structure over conventional at-grade)construction. These costs are dependent upon site conditions,material costs, and labor costs and will differ in various regionsof the country and even among contractors in the same area.Reported costs were found a vary considerably, reflecting bothreal differences in costs of construction and differences in howcosts are allocated.

To provide some guidance as to the magnitude of .coststhat can be expected, ranges of costs have been determinedfor various methods of elevation and structure protection.Values of "average" or "typical" cost are given where possible.These costs, presented in detail below, include all material,labor, and installation costs and are the cost to the consumer.Sources for this information include local building contractors,state and local officials, and various cost estimatingpublications.

The cost information presented here serves only to givethe reader a general idea of the costs of coastal storm-resistantconstruction. These data cannot be directly applied toestimating costs of a structure in a specific community. For this,extensive contacts with local suppliers and contractors will benecessary.

F. 1 FOUNDATIONS

As discussed in Section 4.3.1 of this manual, foundationsystems for residential structures in coastal high hazard areastypically consist of piles or a combination of below-ground pilesand above-ground piers. Costs are presented in the followingsubsections (F.1.1 through F.1.6) for various components ofthese foundation systems, including the piles, pile caps, gradebeams, piers, and pile-to-beam connections.

F.1.1 Wood Piles

F.1.1.1 Types of Wood Piles. Pile foundations, specificallywood pile foundations, are the most commonly used methodfor elevating residential structures in coastal high hazardareas. The piles may terminate at the ground surface or extendupward to the floor beam or roof. Two different types of woodpiles are typically employed--circular and square in crosssection. The selection of "round" (tapered cylindrical) or squarepiles is usually made on the basis of required depth ofembedment, local availability, and custom and does notgenerally represent a cost evaluation. Square piles usuallyhave dimensions of 8 by 8 or 10 by 10 inches, and round pilesare usually 8 inches in tip diameter with a 12-inch butt. Thechoice of method for installing piles--drilling, jetting, or driving--also tends to be a matter of local custom and soil conditions. Anumber of factors affect the cost of positioning piles, such asthe availability of contractors capable of doing this work, costsof mobilizing equipment onsite, and the type of soils to beencountered in driving. For example, in certain areas on theWest Coast where reported pile costs are highest, largeboulders that would prevent pile driving must often be removedbefore piles can be embedded.

F-2 Coastal Construction Manual

F.1.1.2 Wood Pile Costs. The range of costs determined fortypical sizes and lengths of square and round wood piles arepresented in table F-1. The costs for installing the piles--byjetting, driving, or a combination of these methods--arepresented in Table F-2. It was determined that pile installationcan be expected to cost between $90

and $381 per pile for 18-to 30-foot piles (i.e., about $5 to $13per linear foot, installed)). Installation costs typically rangefrom about $2 per linear foot for straightforward installation to$15 per linear foot for difficult installation (e.g., boulders).

TABLE F-1Pile Costs*

Dimensions Member Type (inches) Length (ft) $/ft $/Member

Square Timber 8x8-inch 18 5-10.50 90-188



Square Timber 10x10-inch 24 8.70-15.90 209-381

Round Timber 8-inch-dia. 18 7.50-12.70 135-229

Precast Concrete 10x10-inch 18-30 6.80-16.00 68-160

Precast Concrete 12x12-inch 18-30 9-16.00 90-160

Poured-in Place Concrete Variable 8 8-9.50 65-76

__________________*All costs are 1985 cost to consumer for installed piles.


TABLE F-2

COSTS FOR COMPONENTS OF PILE FOUNDATION

COMPONENT TYPE DIMENSIONS COST ($)

Embedment Drive Piles Not Applicable 2.20-15.00/linear foot

Embedment Jet Piles Not Applicable 1.70-3.40/linear foot

Pile Support Knee Bracing Two-2"x4" or 2"x6" 17.00-27.00/pileMembers

Pile Support Diagonal Bracing Two-2"x6" or 2"x8" 11.00-24.00/setMembers

Grade Beam Reinforced Concrete 8x 16-inch to 7.70-27.50/ft24x 24-inch

Pile Cap Reinforced Concrete Variable 45-330/pile

Timber Pile to Floor Beam Galvanized Bolts 1/2-inch-dia. 2.50-4.00/boltConnections to 1 1/4-inch-dia.


F.1.1.3 Pile Support. Piles are often supported with additionalknee or diagonal bracing between the piles. Knee bracingtypically consists of two 2-by-8-inch boards or one 4-by-4 inchtimber bolted to the pile and floor beam, and can be expectedto cost between $17 and $27 per pile. Diagonal bracing mayconsist of two 2-by-8-inch 3-by-8-inch planks or metal rodsconnected between the piles. The cost for wood diagonalbracing between two piles was determined to be between $11and $24. These costs have been included on Table F-2.

F.1.2 Concrete Piles

Precast concrete piles may also be used for foundationsupport and are installed using a pile driver. At certain sites,subsurface conditions preclude the driving of piles. A method isused in the Florida Keys by which holes are augered andpoured-in-place piles are formed. As presented on Table F- 1,costs for precast piles were determined to be between $7 and$16 per linear foot for ) 10-by-10-inch piles and between $9and $16 per linear foot for 12-by-12-inch piles. Costs of $8 to$9.50 per linear foot were determined for piles developed bythe poured-in-place method.

F.1.3 Pile Caps and Grade Beams

A variation of the pile foundation system includes concreteor wooden piles terminating just below the ground surface andcovered with a pile cap. A grade beam is poured over the pilecaps and connected to the piers elevating the structure toensure stability of the building. pile cap costs are dependentupon the pile dimensions and resultant cap dimensionsrequired, but range in cost between $45 and $330 per pile.Reinforced grade beams range in size from 8 by I 6 inches to24 by 24 inches and in cost from $7.70 to $27.50 per linearfoot. Costs for these two aspects of pile foundations arepresented in Table F-2.

F.1.4 Masonry and Concrete Piers

To elevate the structure above the pile/grade beamsystem, masonry or concrete piers may be employed.Reinforced concrete masonry piers for which cost data areavailable are typically 8 by 16 inches or 12 by 12 inches andrange in price between $2 and $14 per linear foot (includingfooting cost). Reinforced concrete piers are usually moreexpensive than masonry, as verified by the $14 to $48 perlinear foot costs observed for 1-by-2-foot piers, presented inTable F-3. Note that larger (and correspondingly moreexpensive) piers are recommended in this manual, aspresented in Tables A-8 and A-9. These piers would likely cost$20 to $50 per installed foot.

F.1.5 Pile to Floor Beam Connections

Floor beams may be connected to pier and pile systemsby several methods. When the pier or pile is precast reinforcedconcrete, reinforced masonry, or cast-in-place concrete,reinforcement rods or other metal fasteners are provided toconnect to the wooden floor beams or cast-in-place floorbeams. Wooden piles are often bolted to wooden floor beamsusing hot-dipped galvanized bolts and/or metal connectingplates. The cost of the bolts was determined to beapproximately $2.62 per bolt for 1/2-inch-diameter bolts; $2.75per bolt for 5/8-inch -diameter bolts; and between $300 and$385 for the complete pile system using 3/4-inch bolts.

F.2 STRUCTURAL BRACING

In addition to the bracing required to stabilize andsupport the foundation, bracing is required in the structure toresist the wind and water loads in coastal high hazard areas.This bracing includes support between the joist and floorbeam, along the external walls, and between the roof truss andwalls.


F.2.1 Joist to Floor Beam Connection

Floor joists are connected to floor beams using ahurricane clip, which is secured to the beam on one end and tothe joist on the other end. The cost for hurricane clips istypically between $7 and $12 per 100 clips.

F.2.2 Stud Straps and Corner Bracing

Additional support is provided along the external wallsand specifically at the corners by applying stud straps betweenthe studs, and/or by attaching plywood to the corners of thebuilding. Stud straps cost between $.18 and $.29 per strap andplywood costs were determined to range from $.71 to $1.12 perinstalled square foot for 3/8-inch-to 5/8-inch-thick sheeting. These costs are presented in Table F-4.

F.2.3 Roof Truss Connections

In order to provide a continuous connection from the roofto the foundation, hurricane clips are often used to .connect theroof trusses to the building. The same cost of $7 to $12 per100 clips is incurred for these hurricane clips.

F.3 ADDITIONAL COSTS

As discussed in Section 4.3.6, it is usuallyrecommended that all utilities be raised above the BFE. Thecost of elevating utilities is directly related to the height of thestructure and therefore the distance the utilities must be raisedand the additional materials and labor involved. Costs forraising various utilities are presented in Table F-4, andrange from $3 to $16.50 per foot. These elements can beexpected to increase costs between $200 )and $600 perdwelling.

TABLE F-3COSTS FOR PIERS AND SHEAR WALL FOUNDATIONS

Height of Means of Elevation Dimensions (inches) Member (Feet) $/foot $/member Reinforced Concrete Pier 12x24 8-12 14-48.00 112-528.00

Reinforced Concrete Masonry Pier 12x12 or 8x16 8 2.00-13.75 17.-110.00

10 2.50-13.75 24-138.00

12 11.60-13.75 139-165.00


TABLE F-4

COSTS FOR OTHER COMPONENTSOF ELEVATED CONSTRUCTION

Component Cost/Unit ($)

Hurricane clips 7-12/100 clips

Stud straps .18-.19/strap

3/8" plywood sheet (installed) .71-.87/square foot

1/2" plywood sheet (installed) .84-.91/square foot

5/8" plywood sheet (installed) .91-1.12/square foot

Raise water utility 4-8.80/foot

Raise sewer utility 6-16.50/foot

Raise gas utility 4.00/foot

Raise electric utility 3.00/foot

F.3.1 Breakaway Walls

Breakaway walls are sometimes constructed betweenthe grade and elevated first floor. Breakaway walls may beconstructed of lattice work, stud walls, or concrete block, aspresented in Section 4.3.5. For purposes of this study, latticewas assumed to consist of furring over a wood frame; concreteblock breakaway walls were assumed to consist of non-reinforced block with a styrene filler at the top of the block.Since breakaway walls differ from normal walls only in theextent of reinforcing and connection, costs would not beexpected to differ significantly from normal wall costs. Theexpected cost of these three forms of breakaway walls, aspresented in Table F-S, range from $.75 per square foot forlattice work to $2.70 to $3.10 per square foot for concrete blockbreakaway walls.

F.3.2 Other Costs

Several other factors could also add cost to residentialstructures built in coastal high hazard areas. All portions of thebuilding outside of the main structure itself must be securelyattached and anchored. These include porch overhangs,external stairways, and decks. In addition, because thestructure is elevated, all exterior construction above thefoundation will require the use of scaffolding. One builderestimated that this causes a 20 to 30 percent increase in laborcosts.

F.4 COST COMPARISON FOR ELEVATED AND NON-ELEVATED STRUCTURES

The total costs of elevating residential structures incoastal high hazard areas, as previously discussed, dependupon numerous factors. Discussions with builders and localofficials revealed, however, that the additional cost to elevate astructure over the cost of at-grade construction


can be expected to be between $1.30 and $5.10 per squarefoot. This additional cost was also determined to vary with thesize of the structure, with higher additional unit (square foot)costs being associated with larger structures.

For purposes of this study a cost comparison was madefor a 28-by-32-foot building constructed on pilings and onebuilt on a monolithic slab. This analysis indicates not only thecomponents of elevated construction that must be consideredin estimating building costs in coastal high hazard areas, butalso the magnitude of additional cost that can be expected.Costs were obtained from Tables F-I through F-4, and averagecosts were assumed where ranges of costs existed.

For purposes of this example, the lowest floor of thestructure was built 10 feet above grade on 8-by-8inch woodpilings, 24 feet long and arranged in four rows, each containingfour piles. The piles were supported by knee bracing (twobraces per pile) and a 12-by-24-inch grade beam. The pileswere connected to the floor beam using two 5/8-inchgalvanized bolts per pile, and the floor joists were connected tothe floor beam using hurricane clips. The external walls weresupported using stud straps and the thick plywood sheets (twoper corner). A completely tied down system was ensured byapplying hurricane clips to the roof trusses. In addition, theutilities (water supply, sewerage, and electricity) were raised10 feet to the first floor elevation.

TABLE F-5BREAKAWAY WALL COSTS

Type of Wall Dimensions (inches) $/square foot

Lattice Work 1x2 (furring) .75

Stud Wall with Plywood Sheathing 2x4 (16 to 24 O.C.) 1.50-2.00

Block Wall 6 or 8 (thick) 2.70-3.10


TABLE F-6ELEVATION COSTS FOR 28-by-32-FOOT HOUSE

1. Foundationa. Pile Cost

a.1 24-foot 8X8 inch piles x $8.50 per foot = $204 per pilea.2 $204 per pile x 16 piles = $3,264.00

b. Knee bracingb.1 $22 per pile x 16 piles = $352.00

c. Grade Beamc.1 $7.70 per foot x 184 feet = $1,417.00

d. Pile to Floor Beam Connectiond.1 $5.50 per 2-5/8 inch bolts x 16 piles = $88.00d.2 $2.35 per pile labor costs x 16 piles = $38.00

Foundation Total = $5,159

2. Connections and Supporta. Floor Joist to Floor Beam Connection

a.1 44 floor joists x 2 hurricane clips per joist = 88 clipsa.2 $.095 per clip (9.50 per 100) x 88 clips = $8.36a.3 $1.17 per clip labor costs x 88 clips = $103.00

b. Stud Strapsb.1 120 feet of external walls/3 = 40 strapsb.2 40 straps x .29 per strap = $11.60b.3 $1.17 per strap labor costs x 50 straps = $47.00

c. Plywood Corner Bracing (2 sheets per corner)c.1 8 sheets x 32 square feet per sheet = 256 square feetc.2 $.84 per square foot x 256 square feet = $215

d. Roof Truss Connectiond.1 44 roof trusses x two hurricane clips per truss = 88 clipsd.2 $.095 per clip x 88 clips = $8.36d.3 $1.17 per clip labor costs x 88 clips = $103.00

Connections and Support Total = $ 497

3. Utilitiesa. Water

elevated 10 feet above grade x 6.40 per foot = $64.00b. Sewer

elevated 10 feet above grade x 11.50 per foot = $115.00c. Electricity

elevated 10 feet above grade x 3.00 per foot = $30.00

Utilities Total = $ 209 Total for elevating structure = $5,865

A worksheet of the cost calculations is presented inTable F-6. As shown on this sheet, the total cost of elevatingand supporting this structure is approximately $5,865. Sincethe structure is 896 square feet in size, this additional cost ofconstruction is equivalent to $6.54 per square foot. Accordingto Means Residential/Light Commercial Cost Guide (Means,1985), the cost of at-grade cost of at-grade or a one-storyhouse ranges from $35.70 to $44.40 per square foot. Thisadditional cost of $6.54 per square foot, therefore, representsan increase in cost of 15 to 1B percent over at-gradeconstruction.

It should be noted that, although this cost appearshigher than those obtained from builders and officials, thisanalysis represents a complete and more detailed level ofsupport and bracing than is often encountered in coastalconstruction. Typically the foundation system may be lackingthe additional support of the grade beam, which would lowerthe additional cost of construction to $4.96 per square foot or11 to 14 percent of the cost of construction at grade.

Sample Coastal Construction Code G-1

Appendix GSAMPLE COASTALCONSTRUCTION CODE

This sample code is provided for local jurisdictions thatwish to develop a coastal construction code to supplement thegoverning building code. Each jurisdiction will need to tailorthe code provisions to account for specific circumstances, suchas storm history, beach configuration, soil conditions, and localbuilding practices.

The sample code, as presented here, is not intended toprovide detailed design instructions and requirements; rather itprovides a framework through which key elements of coastalconstruction can be identified, thereby assuring their inclusionin the design process. The code is based on the standards forwind loading relationships prepared by the American NationalStandards Institute (ANSI) and for water loading from the Shore Protection Manual , prepared by the Corps of Engineers'Waterways Experiment Station. The NFIP Coastal Construction Manual ( Design and Construction Manual for Residential Structures in Coastal High Hazard Areas ) is alsoreferenced in the code, both as guide to interpreting material inthe ANSI Standards and the Shore Protection Manual , andas a source of supplemental information. Relatively routinelow-rise structures designed solely with the provisions of the Coastal Construction Manual will meet the requirements of thiscode. Although the NFIP manual may offer some guidance,design of larger, unusual, or more complicated structuresshould be undertaken by a design professional to meet therequirements of this code.

1. TITLE

The provisions herein contained shall constitute the"Coastal Construction Codes for (community), (county), (state)"and hereinafter will be referred to as the "Coastal Code."

2. PURPOSE

The purpose of this Coastal Code is to provide minimumstandards for the design and construction of residentialstructures in Coastal High Hazard Areas and adjacent coastalA zone areas where wave action can be expected. The intentof this code is the incorporation of certain nationallyrecommended construction methods and practices so that thepotential damage to an individual structure during stormconditions may be minimized and the public health, safety, andgeneral welfare of the citizens of (community) will be protected.

These standards are intended to supplement the(Standard, BOCA, or Uniform) Building Code, specifically toaddress design factors affecting structural integrity undersevere storm stress and to offer guidance to the designprofessional. In the event of a conflict between the CoastalCode and the (Standard, BOCA, or Uniform) Building Codeand other State or Federal laws or regulations, therequirements resulting in the more restrictive minimum designstandards shall apply.

In addition to the provisions of this Code, it is assumedstructures in Coastal High Hazard Areas would be designedand constructed following standard engineering practice fordetail, completeness, and safety.

G-2 Coastal Construction Manual

3. SCOPE

The requirements of this Code apply to the following:

1. New construction of single family, duplex, andmultifamily residential structures in Coastal HighHazard Areas.

2. Substantial improvement of or additions toexisting residential structures. "Substantialimprovement" means any repair, reconstruction,or improvement of a structure, the estimated costof which equals or exceeds 50 percent of themarket value of the structure. Market value for thepurposes of determining substantialimprovements does not include the value of theland, and shall be determined using standardappraisal techniques, including the marketcomparison approach, cost approach to value (re-placement cost less depreciation), or incomeapproach.

4. DEFINITIONS

ANSI --American National Standards Institute, Inc.

Base Flood--The flood having a 1 percent chance ofbeing equaled or exceeded in any given year, commonlyreferred to as the 100 year flood.

Base Flood Elevation (BFE)--The crest elevation inrelation to mean sea level (using National Geodetic VerticalDatum), expected to be reached during a I 00 year flood whichencompasses the 100 year flood plain.

Breakaway Wall--A wall that is not part of the structuralsupport of the building and is intended through its design andconstruction to collapse under specific

lateral loading forces, without causing damage to the elevatedportion of the building or supporting foundation system.

Coastal High Hazard Area--Area within the 100 yearflood plain that is subject to high velocity waters, caused by(but not limited to) hurricane wave wash. These areas aredesignated as Zones VI-30, VE, or V on the Flood InsuranceRate Map (FIRM).

Column Action--Potential elastic instability in piles orcolumns resulting in buckling or lateral bending of the member,resulting from compressive stresses due to direct axial andbending loads.

Dead Load--Passive weight of all permanentconstruction in a building or structure, including walls, floors,roofs, stairways, and fixed service equipment.

Erosion --Wearing away of land by the action of naturalforces. On a beach, the carrying away of beach material bywave action, tidal currents, littoral currents, or by deflation.

Grade --Average elevation of the ground, paved orunpaved, adjoining a building or structure.

Grade Beams --Wood timber or reinforced concretebeams located at or below grade elevation, and extendingaround the perimeter and through the interior of a building, thatsecurely interconnect and distribute lateral loads among thefoundation piles or piers.

Landward --In a direction away from the water.

Live Load--Weight superimposed upon the building orstructure by its use and occupancy and not attributable toenvironmental loads such as water and wind or dead load.


Pile Clus ter --A group of piles in close proximity that aretied together by a pile cap and function as a unit.

Piling Foundation --Includes pilings used as columnsand those terminating below grade at pile caps, providing thesupport of a structure.

Residential Structure --Any building or portion thereofthat is designed, built, rented, or leased to be occupied as ahome or residence by one or more persons or families.

Stable Soil Elevation --Minimum elevation of soilresulting from erosion or scour. The design erosion or scour ata site depends on site elevation and soil type, in combinationwith the Base Flood Elevation.

Structure --That which is built or constructed, an edificeor building of any kind, or any piece of work artificially built up,compounded of parts joined together in some definite manner.

Uplift Pressure --Forces acting vertically upward on thebase, deck, or floor of the structure by positive or negativepressure.

5. ELEVATION STANDARDS

No new construction or substantial improvements areallowed seaward of (specify established setback line orspecific setback distance from shoreline points, such as themean high tide line (minimum requirement) or vegetation ordune line). All new construction or substantial improvementsshall be elevated on pilings or columns such that the lowesthorizontal structural member supporting the lowest elevatedfloor (excluding columns, piles, diagonal bracing attached tothe piles or columns, grade beams, pile caps, slabs, and othermembers designed to either withstand storm action or breakaway without imparting damaging loads to the structure) iselevated to or above the BFE.

6. DETERMINATION OF LOADING FORCESStructural design in Coastal High Hazard Areas shall considerthe effects of wind and water loads acting simultaneouslyduring the Base Flood on all building components. The designconditions for those loadings are presented in Section 6.1 forwater and Section 6.2 for wind loads. Equations, procedures,and other guidance for determining and utilizing design valuesfor these loadings are available in the documents referenced inSection 14.

6.1 WATER LOADSThe structural design shall be adequate to resist water

forces that would occur during the Base Flood. Horizontalwater loads considered shall include inertial and drag forces ofwaves, current drag forces, and impact forces from waterbornestorm debris. Dynamic uplift loads shall also be considered ifbulkheads, walls, or other natural or manmade flowobstructions could cause wave runup beyond the BFE.

6.2 WIND LOADSBuildings shall be designed and constructed to resist the

forces due to wind pressure. Wind forces on thesuperstructure include windward and leeward forces onvertical walls, uplift on the roof, internal forces when openingsallow wind to enter the house, and upward force on theunderside of the house when it is exposed. In the design, thewind should be assumed to blow potentially from any lateraldirection relative to the house.

Design wind pressures on a building and its compo-nents are derived from wind velocities associated with stormswith a 100 year mean recurrence interval. The 100 year designwind velocity is to be taken as (specify) mph. The designmethod to be used is that set forth by the American NationalStandards Institute, Section A58.1 - 1982.


7. FOUNDATION STANDARDS

All structures erected in Coastal High Hazard Areasshall be supported on pilings or columns and adequatelyanchored to such supports to resist collapse and lateralmovement from wind velocity and water pressures determinedin accordance with Sections 6.1 and 6.2. Spread footingsand fill shall not be used for structural support purposes.Foundations must be designed to transfer safely to theunderlying soil all loads due to wind, water, dead load, liveload, and other loads (including uplift due to wind and water).(NOTE: Foundation standards may require modification by thelocal jurisdiction if unusual soil or rock conditions dictate theuse of special foundation systems.)

7.1 PILE FOUNDATION DESIGN

7.1.1 Pile Spacing

The design ratio of pile spacing to pile diameter shall notbe less than (8):1 for individual piles; however this would notapply to pile clusters located below the design grade. Themaximum center-to-center spacing of wood piles shall not bemore than (12)* feet on center under load bearing sills, beams,or girders.

7.1.2 Pile Embedment

Pilings shall have adequate soil penetration (bearingcapacity) to resist the combined wave and wind loads (lateraland uplift) determined in accordance with Sections 6.1 and 6.2,acting simultaneously with typical structure (live and dead)loads, and shall include consideration of decreased resistancecapacity caused by erosion of soil___________________*Values given in parentheses are suggested, and subject tolocal modification.

strata surrounding the piles. The minimum penetration forfoundation piles is to an elevation of (5) feet below mean sealevel (msl) datum if the BFE is +10 msl or less, or to at least (10)feet below msl if the BFE is greater than +10 msl. Additionalguidance on pile embedment, including load/embedmenttables for different soil and pile types, is provided in the Coastal Construction Manual .

7.1.3 Column Action

Pile foundation analysis shall also include considerationof piles in column action from the bottom of the structure to thestable soil elevation of the site. Pilings may be horizontally ordiagonally braced to withstand wind and water forces.

7.1.4 Pile Standards

The minimum acceptable sizes for timber piles are a tipdiameter of (8) inches for round timber piles and (8) by (8)inches for square timber piles. All wood piles must be treated inaccordance with requirements of AWPA-C3 to minimize decayand damage from fungus.

Reinforced concrete piles shall be cast of concretehaving a 28-day ultimate compressive strength of not less than5,000 pounds per square inch, and shall be reinforced with aminimum of four longitudinal steel bars having a combinedarea of not less than 1 percent nor more than 4 percent of thegross concrete area. Reinforcement for precast piles shallhave a concrete cover of not less than 1-1/4 inches for No. 5bars and smaller and not less than 1-1/2 inches for No. 6through No. 11 bars. Reinforcement for piles cast in the fieldshall have a concrete cover of not less than 2 inches.


7.1.5 Pile Installation

Piles shall be driven by means of a pile driver or drophammer, jetted, or augered into place.

7.1.6 Bracing

Additional support for piles in the form of bracing is oftenrequired to resist horizontal forces. This bracing may includelateral or diagonal bracing between piles.

Piles shall be braced at the ground line in bothdirections by a wood timber grade beam, a reinforced concretegrade beam, or a concrete slab deepened and reinforced atthe edges. These at-grade supports should be securelyattached to the piles to provide support even if scoured frombeneath.

Diagonal bracing between piles, consisting of 2-inch-by-(8)-inch (minimum) members bolted to the piles, shall belimited in location to below the lowest supporting structuralmember and above the stable soil elevation, and in the verticalplane along pile rows perpendicular to the shoreline.Galvanized steel rods (minimum diameter (1/2) inch) or cabletype bracing is permitted in any plane.

Knee braces, which stiffen both the upper portion of apile and the beam-to-pile connection, may be used along pilerows perpendicular and parallel to the shoreline. Knee bracesshall be 2-by-8 lumber bolted to the sides of the pile/beam, or4-by-4 or larger braces framed into the pile/beam. Boltingshall consist of two (5/8)-inch galvanized steel bolts (eachend) for 2-by-8 members, or one (5/8)-inch lag bolt (each end)for square members. Knee braces shall not extend more than 3feet below the BFE.

7.2 COLUMN FOUNDATION DESIGN

Masonry piers or poured-in-place concrete piers shallbe internally reinforced to resist vertical and lateral loads, andbe connected with a moment-resisting connection to a pile capor pile shaft. Additional guidance on pier construction isprovided in the Coastal Construction Manual .

8. ANCHORING STANDARDS

All buildings and structures must have all componentsadequately anchored and continuously connected from thefoundation to the roof, to prevent flotation, collapse, orpermanent lateral movement during the Base Floodconcurrent with the 100 year design wind velocity.

8.1 CONNECTORS AND FASTENERS

Galvanized metal connectors, wood connectors, or boltsof size and number adequate for the calculated loads must beused to connect adjoining components of a structure. Toenailing as a principal method of connection is not permitted. Allmetal connectors and fasteners used in exposed locationsshall be steel, hot-dipped galvanized after fabrication. Connectors in protected interior locations shall be fabricatedfrom galvanized sheet.

8.2 BEAM TO PILE CONNECTIONS

The primary floor beams or girders shall span thesupports in the direction parallel to the flow of potential;floodwater and wave action and shall be fastened to thecolumns or pilings by bolting, with or without cover plates.Concrete members shall be connected by reinforcement, if castin place, or (if precast) shall be securely connected bolting orwelding. If sills, beams, or girders are attached to wood pilingat a notch, a minimum of two (5/8)-inch galvanized steel boltsor two hot-dipped galvanized straps


(3/16 inch by 4 inches by 18 inches) each bolted with two (1/2)-inch lag bolts per beam member, shall be used. Notching ofpile tops shall be the minimum sufficient to provide ledgesupport for beam members without unduly weakening pileconnections. Piling shall not be notched so that the crosssection is reduced below 50 percent.

8.3 FLOOR AND DECK CONNECTIONS

Wood 2- by 4-inch (minimum) connectors or metal joistanchors shall be used to tie floor joists to floor beams/girders.These should be installed on alternate floor joists, at aminimum. Cross bridging of all floor joists shall be provided.Such cross bridging may be 1- by (3)-inch members, placed 8-feet-on-center maximum, or solid bridging of same depth asjoist at same spacing.

Plywood should be used for subflooring and atticflooring to provide good torsional resistance in the horizontalplane of the structure. The plywood should not be less than(3/4)-inch total thickness, and should be exterior grade andfastened to beams or joists with 8d annular or spiral threadgalvanized nails. Such fastening shall be supplemented bythe application of waterproof industrial adhesive applied to allbearing surfaces.

8.4 EXTERIOR WALL CONNECTIONS

All bottom plates shall have any required breaks under awall stud or an anchor bolt. Approved anchors will be used tosecure rafters or joists and top and bottom plates to studs inexterior and bearing walls to form a continuous tie. Continuous15/32-inch or thicker plywood sheathing-overlapping the topwall plate and continuing down to the sill, beam, or girder--maybe used to provide the continuous tie. If the sheets of plywoodare not vertically continuous, then 2-by-4 nailer blocking shallbe provided at all horizontal joints. In lieu of the plywood,

galvanized steel rods (1/2-inch diameter) or galvanized steelstraps not less than I inch wide by 1/16 inch thick may be usedto connect from the top wall plate to the sill, beam, or girder.Washers with a minimum diameter of 3 inches shall be used ateach end of the 1/2-inch round rods. These anchors shall beinstalled no more than (2) feet from each corner rod, no morethan (4) feet on center.

8.5 CEILING JOIST/RAFTER CONNECTIONS

All ceiling joists or rafters shall be installed in such amanner that the joists provide a continuous tie across therafters. Ceiling joists and rafters shall be securely fastened attheir intersections. A metal or wood connector shall be used atalternate ceiling joist/rafter connections to the wall top plate.

Gable roofs shall be additionally stabilized by installing2-by-4 blocking on 2-foot centers between the rafters at eachgable end. Blocking shall be installed a minimum of 8 feettoward the house interior from each gable end.

8.6 PROJECTING MEMBERS

All cantilevers and other projecting members must beadequately supported and braced to withstand wind and wateruplift forces. Roof eave overhangs shall be limited to amaximum of 2 feet and joist overhangs to a maximum of 1 foot.Larger overhangs and porches will be permitted if designed orreviewed by a registered professional engineer or architectand certified in accordance with Section 13 of this Code.

9. ROOF SHEATHING

Plywood, or other wood material, when used as roof sheathing,shall not be less than (15/32) inch in thickness,


and shall be of exterior sheathing grade or equivalent. Suchsheathing shall be fastened to rafter or truss assemblies in themanner required by the (applicable) Building code. Allattaching devices for sheathing and roof coverings shall begalvanized or be of other suitable corrosion resistant material.

All corners, gable ends, and roof overhangs exceeding(6) inches shall be reinforced by the application of waterproofindustrial adhesive applied to all bearing surfaces of anyplywood sheet used in the sheathing of such corner, gableend, or roof overhang.

In addition, roofs should be sloped as steeply aspracticable to reduce uplift pressures, and special care shouldbe used in securing ridges, hips, valleys, eaves, vents,chimneys, and other points of discontinuity in the roofingsurface.

10. PROTECTION OF OPENINGS

All exterior glass panels, windows, and doors shall bedesigned, detailed, and constructed to withstand loads due tothe design wind speed of (specify) mph. Connections for theseelements must be designed to transfer safely the design loadsto the supporting structure. Panel widths of multiple panelsliding glass doors shall not exceed 3 feet. Storm shutters orother types of protective panels are recommended foradditional protection of openings.

11. USE OF SPACE BELOW THE LOWEST ELEVATEDFLOOR

All new construction and substantial improvementswithin the Coastal High Hazard Zone must have the spacebelow the lowest floor either free of obstruction or constructedwith nonsupporting breakaway walls, open wooden latticework, or insect screening intended to fail under

wind and water loads associated with the base flood withoutcausing collapse, displacement, or other structural damage tothe elevated portion of the building or supporting foundation.Enclosed space may be used solely for vehicular parking andfor building access (stairs, stairwells, and elevator shafts).

11.1 BREAKAWAY WALL DESIGN STANDARDS

The breakaway wall shall have a design safe loadingresistance of not less than (specify) and not more than (specify,but not more than 20) pounds per square foot, with the criterionthat the safety of the overall structure at the point of wall failurebe confirmed using established procedures. Grade beamsshall be installed in both directions for all piles considered tocarry the breakaway wall load. Knee braces are required forfront row piles that support breakaway walls. (NOTE: Loadingstrengths may be governed by code requirements for minimumdesign wind velocity pressures. Use of a 10 PSF value isgenerally recommended since it would allow for wall failureonly under hurricane (greater than 75 mph) wind speedconditions.)

11.2 CERTIFICATION OF BREAKAWAY WALLS

Breakaway wall strengths above 20 PSF are not gen-erally recommended for detached or low rise residentialconstruction. However, in those cases where such wallstrengths are to be considered the following criteria should beused.

Use of breakaway wall strengths in excess of 20 PSFshall not be permitted unless a registered professionalengineer or architect has developed or reviewed the structuraldesign and specifications for the building foundation andbreakaway wall components, and certifies that (1) thebreakaway walls will fail under water loads less than those thatwould occur during the base flood; and (2) the elevated


portion of the building and supporting foundation system willnot be subject to collapse, displacement, or other structuraldamage due to the effects of wind and water loads (bothhaving a 100 year mean recurrence interval) actingsimultaneously on all building components.

12. UTILITIES

All machinery and equipment servicing the building must beelevated to or above the BEE, including heating, ventilating,and air conditioning equipment, hot water heaters, appliances,elevator lift machinery, and electrical junction and circuitbreaker boxes. Sanitary sewer and storm drainage systemsthat have openings below the BFE shall be provided withautomatic backflow valves or other automatic backflow devicesthat are installed in each discharge line passing through abuilding exterior wall.

13. CERTIFICATION REQUIREMENTS

For all new and substantial improvements to residentialstructures in the Coastal High Hazard Area, building permitapplications shall be accompanied by design plans andspecifications, prepared in sufficient detail to enableindependent review of the foundation support and connectioncomponents to be used in meeting Sections 7 and 8 of thisCode. Said plans and specifications shall be developed orreviewed by a registered professional

engineer or architect, and shall be accompanied by astatement, bearing the signature of the architect or engineer,certifying that the design and methods of construction to beused are in accordance with accepted standards of practiceand with all applicable provisions of this Code.

14. REFERENCE DOCUMENTS

Standard reference documents for use with this Code indetermining design wind and water forces on structures are:

Wind --American National Standards Institute, Inc., Minimum Design Loads for Buildings and Other Structures , ANSIA58.1 - 1982 (New York, 1982).

Water --Waterways Experiment Station, Shore Protection Manual , two volumes, Department of the Army, Corps ofEngineers, Coastal Engineering Research Center(1984).

Guidance on the application of information from the abovereference documents, together with other design data andprocedures, is provided in:

Federal Emergency Management Agency, Coastal Construction Manual (Washington, D.C., 1986).

Individuals Contacted During Study H-1

Appendix HINDIVIDUALS CONTACTEDDURING STUDY

(1) Contacted during preparation of First Edition, 1981.

(2) Contacted during preparation of Second Edition, 1986.

(1,2) Contacted during preparation of both 1981 and 1986editions.

Adler, Harold, AIA (Charleston, South Carolina) (1)

Ainslie, Richard, AIA (Houston, Texas) (1)

Aiu, Boniface (Chief, Honolulu Fire Department, Honolulu,Hawaii) (1)

Allread, Jess (North Carolina Department of Insurance,Engineering Division) (2)

Anderson, Max (Building Department, Sanibel Island, Florida)(2)

Aspinwall, Jerry (Building Director, Monroe County, Florida)(2)

Atkinson, Donald (Building Inspector, Rockport,Massachusetts) (1)

Atwood, Clayton (Sea Pines Corporation, Land DevelopmentDivision, Hilton Head, South Carolina) (1)

Aultman, James (Aultman Construction, Key West, Florida)

Baily, Brenden (Federal Disaster Assistance Administration,Region I, Boston, Massachusetts) (1)

Benson, John (David A. Crane Partners/DACP, Inc., Boston,Massachusetts) (1)

Blackledge, Ben (County Building Inspector, Galveston,Texas)(1)

Bohn, John (Administrator, Oahu Civil Defense Agency,Honolulu, Hawaii) (I)

Bratlin, George (Technical Director, State Building CodeCommission, Boston, Massachusetts) (1)

Bretshneider, Charles L., Ph.D. (University of Hawaii,Department of Ocean Engineering, Honolulu, Hawaii;Tsunami Technical Advisory Committee) (1)

Cahill, John C., AIA (John C. Cahill Associates, Inc.,Washington, D.C.) (1)

Camara, L. (Honolulu Fire Department, Honolulu, Hawaii) (1)

Cameron, Lyle (Cameron Construction, Key West, Florida) (2)

Cantrell, Ralph (North Carolina Office of Coastal Management,Dare County, North Carolina) (1)

Carmichael, Thad (Director, Building Division, New HanoverCounty, North Carolina) (1)

H-2 Coastal Construction Manual

Cassell, Robert D., Jr. (FEMA Region IV, Atlanta, Georgia) (1)

Chamberlain, John (Builder, Pensacola, Florida) (1)

Chan, John, S.E. (Consulting Structural Engineer, Van Nuys,California) (1)

Chun, K.K. Calvin (Executive Director, Council of Housing andConstruction Industry, Honolulu, Hawaii) (1)

Collins, Ian J., Ph.D., P.E. (Vice President and Chief Engineer,Tetra Tech, Inc., Pasadena, California) (1)

Colville, Richard (Architect, Monroe County, Florida) (2)

Cox, Doak C., Ph.D. (Director, University of Hawaii, En-vironmental Center, Honolulu, Hawaii; TsunamiTechnical Advisory Committee) (1)

Craven, John (University of Hawaii, Honolulu, Hawaii) (1)Davis, Bill (Building Inspector, Panama City, Florida) (1)Davis, Emery (Building Inspector, Gulfport, Mississippi) (1)

DeMary, Henry (Chief Building Inspector, Galveston, Texas)(1)

DeMenthe, Larry (U.S. Army Corps of Engineers, New Orleans,Louisiana) (1)

Deverall, Mr. and Mrs. Alex (Homeowners, Orange County,California) (1)

Dobson, Bill (Building Inspector, Marshfield, Massachusetts)(1)

Donald, W.M. (Building Inspector, Isle of Palms, SouthCarolina) (1)

Doyel, Carol (Federal Insurance Administration, Region IV,Atlanta, Georgia) (1)

Duane, David B. (U.S. Department of Commerce, NationalOceanic and Atmospheric Administration, Office of SeaGrant, Gaithersburg, Maryland) (1)

Eberly, John (U.S. Department of Commerce, National Oceanicand Atmospheric Administration, Rockville, Maryland) (I)

Fau, Charles (AM FAC Committees) (1)

Feinman, David (Builder, Sand & Sea Properties, Galveston,Texas) (1,2)

Ferragamo, Stanley (Building Inspector, Revere,Massachusetts) (1)

Foster, Norman (Director of Inspection Services, City of Mobile,Alabama) (1)

Frank, Neil (U.S. Department of Commerce, National Oceanicand Atmospheric Administration, Hurricane Disaster Center,Miami, Florida) (1)

Gariss, Howard (Architect, Ligon B. Flynn Architect AIA,Wilmington, North Carolina) (2)

Goforth, George (Defense Civil Preparedness Agency,Washington, D.C.) (1)

Grabiel, Paul (Building Inspector, Galveston, Texas) (1)


Graves, Bill, AIA (Pensacola, Florida) (1)

Gregory, Walter (Building Inspector, Dare County, NorthCarolina) (1)

Grooms, Robert (City Administrator, Folly Beach, SouthCarolina) (1)

Gross, Jim (U.S. Department of Commerce, National Bureauof Standards, Codes Office, Gaithersburg, Maryland) (1)

Guscio, Frank (Sea Pines Corporation, Architectural ReviewBoard, Hilton Head, South Carolina) (1)

Hale, John (County Engineer for Coastal Problems, LosAngeles, California) (1)

Hanna, James (Architect, Maryland Housing Office) (I)

Hansford, Don (Federal Insurance Administration, Region IV,Atlanta, Georgia) (1)

Haralson, James (Building Inspector, Georgetown County,South Carolina) (1)

Harris, Bill (Federal Insurance Administration, Region IV,Atlanta, Georgia) (1)

Harris, Mike (County Engineer, Galveston County, Texas) (1)

Henry, Robert (Delaware Department of Natural Resources,Soil and Water Conservation Service, Beach PreservationSection, Dover, Delaware) (1)

Hickman, Raymond J. (Hickman Real Estate, Bethany KBeach, Delaware) (1)

Higa, Jinji (City and County of Honolulu, Building SafetyDivision, Honolulu, Hawaii) (1)

Hirota, Dennis (Sam 0. Hirota, Inc., Honolulu, Hawaii) (1)

Holmes, Dwight (Architect, Rowe Holmes Barnett Architects,Inc., Tampa, Florida) (2)

Huggins, Dub (Building Inspector, City of North Myrtle Beach,South Carolina) (2)

Hughes, John (Delaware Department of Natural Resources,Soil and Water Conservation Service, Beach PreservationSection, Dover, Delaware) (1)

Hunter, Robert J. (Federal Insurance Administration,Washington, D.C) (1)

Indler, EIvan (Electronic Data Systems, Rockville, Maryland)(1)

Ivey, John (Federal Insurance Administration, Region VI,Dallas, Texas) (1)

Jacobs, Paul (U.S. Department of Commerce, NationalOceanic and Atmospheric Administration, National WeatherService, Silver Spring, Maryland) (1)

Johnson, Ray (Gay and Taylor, Insurance Adjustors, MyrtleBeach, South Carolina) (2)

Johnston, Henry (Johnston Architects, Wilmington, NorthCarolina) (2)

Jones, Chris (Coastal Engineer, Florida Sea Grant ExtensionProgram, Gainesville, Florida) (2)

Keith, John, P.E. (Consulting Engineer, Galveston, Texas) (1)


Kimura, George, P.E. (U.S. Army Corps of Engineers, PacificOcean Division, Flood Plain Management Section,Honolulu, Hawaii) (1)

Kirkpatrick, Sally (Legislative Assistant, American InsuranceAssociation, Washington, D.C.) (1)

Kittridge, David (Private Consultant, Miami, Florida) (1, 2)

Kopacka, Bill (Planning Director, Charleston County, SouthCarolina) (1)

Krahl, Nat, Ph.D. (Consulting Engineer, Nat Krahl andAssociates, Houston, Texas) (1)

Kugler, John (Building Inspector, Gulf Shores, Alabama) (1)

Lakey, Mr. (Building Inspector, Folly Beach, South Carolina)(1)

Lash, Doug (Federal Insurance Administration, Washington,D.C.) (1)

Latimer, Mr. (Builder, Galveston, Texas) (I)

Lee, Edgar (Tsunami Technical Advisory Committee,Honolulu, Hawaii) (1)

Lee, Jake, AIA (Lee and Partners, Hilton Head, SouthCarolina) (1)

Lewin, Kermit (Chairman, Planning Board, Monroe County,Florida) (1)

Lewis, Lynwood (Building Inspector, Mobile County, Alabama)(1)

Leyendecker, E.P. (U.S. Department of Commerce, NationalBureau of Standards, Gaithersburg, Maryland) (1)

Loomis, Harold, Ph.D. (U.S. Department of Commerce,National Oceanic and AtmosphericAdministration/University of Hawaii, Joint TsunamiResearch Effort, Honolulu, Hawaii) (1)

Lopez, A. (Honolulu Fire Department, Honolulu, Hawaii) (1)

Marks, Jim (Private Consultant, Miami, Florida) (I)

Mason, Rick (Federal Insurance Administration, Region IV,Atlanta, Georgia) (1)

McBeth, Robert (FEMA Region IV, Atlanta, Georgia) (2)

McDonald, Allen (Building Inspector, Quincy, Massachusetts)(1)

McLeod, Mr. (Builder, Galveston, Texas) (1)

Mercom, John (Consulting Engineer, Nat Krahl andAssociates, Houston, Texas) (1)

Meredith, Burgess (Homeowner, Malibu Beach, California) (1)

Merli, Kevin (Federal Insurance Administration, Region I,Boston, Massachusetts) (1)

Mieremet, Ben (Hazards Coordinator, Coastal ManagementDivision, NOAA, Washington, DC) (2)

Miller, Crane (Scheaffer & Roland, Consulting Engineers,Chevy Chase, Maryland) (I)


Miller, Mike (Zoning Administrator, Sarasota County, Florida)(2)

Miller, Paul, AIA (Lee and Partners, Architects, Hilton Head,South Carolina) (I)

Minor, Joseph (Director, Institute for Disaster Research, TexasTech University, Lubbock, Texas) (2)

Mixon, Charles (City Engineer, Tarpon Springs, Florida) (2)

Montgomery, Harry (Builder, Galveston, Texas) (1)

Moore, Robert B. (Assistant Administrator, Oahu Civil DefenseAgency, Honolulu, Hawaii) (1)

Morelli, Ugo (Federal Disaster Assistance Administration,Washington, D.C.) (1)

Munn, Chuck (Fripp Island Development Corporation,Beaufort County, South Carolina) (1)

Muraoka, Arthur (Department of Land Utilization, City andCounty of Honolulu, Hawaii) (1)

Muraoka, Herbert (Chief of Building Safety, City and County ofHonolulu, Hawaii) (1)

Myers, Dalton (Building Inspector, Georgetown County, SouthCarolina) (1)

Myers, Vance, Ph.D. (U.S. Department of Commerce,National Oceanic and Atmospheric Administration,Washington, D.C.) (1)

Nesbitt, John (Director of Public Works, Wrightsville Beach,North Carolina) (2)

Nielson, Susan (County Building Inspector, Galveston, Texas)(1)

Onufer, Andrea (Assistant Building Director, City of Clearwater,Florida) (2)

Palmeiri, Peter (Schoenfield Associates, Inc., Boston,Massachusetts) (1)

Patrick, George (Defense Civil Preparedness Agency, RegionI, Boston, Massachusetts) (1)

Patterson, James C. (Sea Scaping Construction Company,Destin, Florida) (1)

Peoples, Bryon (Building Official, Pensacola, Florida) (1)

Perry, John (Commonwealth of Massachusetts, StateDisaster Recovery Team, Boston, Massachusetts) (1)

Peteet, Frank, AIA (Inspection Department, GeorgetownCounty, South Carolina) (I)

Peterson, Dale (Federal Insurance Administration, RegionIX, San Francisco, California) (1)

Phippen, George (U.S. Army Corps of Engineers, CoastalEngineering Research Center, Washington, D.C.) (1)

Raban, Truitt (Landscape Architect, Edward Pinchney, HiltonHead, South Carolina) (1)

Ragin, Donald (State of Texas, Division of Water Resources)(2)

Ray, Glenn (Builder, Grayson Enterprises, WrightsviIle Beach,North Carolina) (2)


Rice, Derwood (Building Inspector, Craven County, NorthCarolina) (1)

Richardson, Bill (Anderson-Nichols & Co., Inc., Boston,Massachusetts; Scituate Conservation Commission) (1)

Rogers, Spencer M., Jr. (Department of Civil Engineering,North Carolina State University and UNC Sea Grant,Marine Advisory Services, Kure Beach, North Carolina)(2)

Rowland, Bill (Homeowner and Builder, Malibu Beach,California) (1)

Russell, Joe (Federal Disaster Assistance Administration,Washington, D.C.) (1)

Saconas, Edward S. (Developer, Hitchcock, Texas) (1)

Sandifer, Tony (Building Official, Santa Rosa IslandAuthority, Pensacola Beach, Florida) (1)

Selder, Mr. (Building Inspector, Edisto Beach, SouthCarolina) (1)

Sharp, Dr. (University of Florida, Gainesville, Florida) (1)

Sheffer, James M. (General Manager, Santa Rosa IslandAuthority, Pensacola Beach, Florida) (1)

Shima, Howard M. (Chairman, Tsunami Subcommittee,Structural Engineering Association of Hawaii, Honolulu,Hawaii) (1)

Shumpert, Horace (Consulting Engineer, Pensacola,Florida) (1,2)

Sims, James (Professor of Civil Engineering, RiceUniversity, Houston, Texas) (1)

Smith, Jim (Federal Insurance Administration, Region IV,Atlanta, Georgia) (1)

Smith, Louis (Oahu Civil Defense Agency, Honolulu, Hawaii)(1)

Sparks, Peter R. (Assoc. Professor of Civil Engineering andEngineering Mechanics, Clemson University, Clemson,South Carolina) (2)

Spears, R.E. (Building Official, Galveston, Texas) (1)

Standley, David (Commissioner, Massachusetts Department ofEnvironmental Quality Engineering, Cambridge,Massachusetts) (1)

Stewart, Paul (Assistant Building Director, Lee County, Florida)(2)

Stluka, Willard J. (Chairman, Tsunami Technical AdvisoryCommittee, Honolulu, Hawaii) (1)

Stone, Bill (Building Inspector, Scituate, Massachusetts) (1)

Sullivan, Mr. (Builder, Galveston, Texas) (1)

Teagle, C.R. (Builder, Pensacola, Florida) (1)

Teale, Sandy (Building Inspector, Beaufort County, SouthCarolina) (I)

Thomas, Edward A. (Federal Insurance AdministrationRegional Director, Region I, Boston, Massachusetts) (1)


Thompson, Jerry (Thompson Construction, Myrtle Beach,South Carolina) (2)

Timely Corporation (San Antonio, Texas; Contact made withbuilder) (1)

Tom, S. (Honolulu Fire Department, Honolulu, Hawaii) (1)

Tubbs, Townsend (Builder, Bethany Beach, Delaware) (1)

Ushijima, Thomas M., P.E. (U.S. Army Corps of Engineers,Pacific Ocean Division, Flood Plain ManagementCoordinator, Honolulu, Hawaii) (1)

Weiss, David C., S.E. (Consulting Structural Engineer, Encino,California) (1)

West, James (Mike Evans & Co., Bethany Beach, Delaware)(2)

White, Fred R., AIA (Architects Hawaii, Ltd., Honolulu, Hawaii;Tsunami Technical Advisory Committee) (1)

Wicks, Bill (Building Inspector, New Hanover County, NorthCarolina) (1)

Wilcox, Ed (Building Inspector, Beaufort County, SouthCarolina) (1)

Woodward, Glenn (Federal Insurance Administration,Regional Director, Region IV, Atlanta, Georgia) (1)

Yuasa, Ernest T. (Hawaiian Telephone Company, Honolulu,Hawaii; Tsunami Technical Advisory Committee) (1)

Zensinger, Larry (Federal Insurance Administration,Washington, D.C.) (1)

Bibliography I-1

Appendix IBIBLIOGRAPHY

Alpeirn, Lynn M., Custodians of the Coast: History of the United States Army Engineers at Galveston (U.S. Army Corps ofEngineers, Galveston District; 1977).

The American Institute of Architects Foundation, Elevated Residential Structures, prepared for Federal EmergencyManagement Agency, FEMA 54 (1984).

American Institute of Timber Construction, Timber Construction Manual , Second Edition (John Wiley and Sons, Inc., 1974).

American Insurance Association, Catastrophe Loss History Coastal Areas D elaware and New Jersey (Property ClaimService, May 12, 1970).

American National Standards Institute, Building Code Requirements for Minimum Design Loads in Buildings and Other Structures , ANSI A58.1 - 1972 (New York, 1972).

American National Standards Institute, Inc., Minimum Design Loads for Buildings and Other Structures , ANSI A58.1-1982(New York, 1982).

American Plywood Association, Plywood Construction Guide (published annually).

American Wood-Preservers' Association, All Timber Products--Preservative Treatment by Pressure Processes , Standard No. C1-84 (Stevensville, Maryland; 1984).

American Wood Preservers Institute, FHA Pole Construction (McLean, Virginia; 1975).

Anderson, L.O., and Walton R. Smith, Houses Can Resist Hurricanes , U.S. Forest Service Research Paper FPL 33,U.S. Department of Agriculture, Forest Service (ForestProducts Laboratory, Madison, Wisconsin; August 1965).

Bretschneider, Charles, and Peter G. Wybro, Inundations and Forces Caused by Tsunamis for the State of Hawaii ,Technical Supplement No. 5 to the Hawaii Coastal ZoneManagement Program (1978).

Building Officials & Code Administrators International, Inc., The BOCA Basic National Building Code/1 984 , Ninth Edition.

Building Officials and Code Administrators International, Inc., The BOCA Basic Building Code/1 978; Model Building Regulations for the Protection of Public Health, Safety and Welfare , Seventh Edition (1978).

Burdin, Walter W., "Surge Effects from Hurricane Eloise," Shore and Beach , Vol. 45, No. 2 (American Shore and BeachPreservation Association, April 1977).

Chen, Michael, Tsunami Propagation in Response to Coastal Areas , Publication No. HIG 73-15 (University ofHawaii, Hawaii Institute of Geophysics; 1973).

Chiu, Arthur N. L., Luis E. Escalante, J. Kenneth Mitchell, DaleC. Perry, Thomas A. Schroeder, and Todd Nalton, Hurricane Iwa, Hawaii, November 23, 1982 , Committee onNatural Disasters, Commission on Engineering andTechnical Systems, National Research Council (NationalAcademy Press, Washington, D.C.; 1983).

I-2 Coastal Construction Manual

Collier, C.A., Building Construction on Shoreline Property: A Checklist (Florida Cooperative Extension Service, MarineAdvisory Program).

Collier, Courtland A., "Bulkhead and RevetmentEffectiveness, Cost and Construction," 2nd Edition (State ofFlorida, Department of Natural Resources; November 1976.

Collier, C.A., Construction Guidelines to Minimize Hurri cane Damage to Shore Area Homes , (Florida Department ofNatural Resources, November 1976).

Collier, Court land A., Kamran Eshaghi, George Cooper, andRichard S. Wolfe, Guidelines for Beachfront Construction with Special Reference to the Coastal Construction Setback Line , Sea Grant Program Report No. 20, StateUniversity System of Florida (sponsored by State ofFlorida, Department of Natural Resources, Bureau ofBeaches and Shores; February 1977).

Cox, Doak and Joseph Morgan, Local Tsunamis and Possible Local Tsunamis in Hawaii , Publication No. HIG-77-l4(University of Hawaii, Hawaii Institute of Geophysics;November 1977).

Defense Civil Preparedness Agency, Interior Guidelines for Building Occupant Protection from Tornadoes and Extreme Winds , Report TR-83A (U.S. Department of Defense, 1975).

Delaware Coastal Zone Management Program, Coastal Storm Damage Report 1923-1974 , Technical Report No. 4, Document No. 1003-78-01-05 (September 1977).

Edge, W.L., J. S. Fisher, W. O. Connor, and S. Nnaji, "ASupplement to the Southern Building Code for HurricaneProtection," sponsored by The South Carolina CoastalCouncil, Department of Civil Engineering ClemsonUniversity, 1984).

Federal Emergency Management Agency, Elevating to the Wave Crest Level, A Benefit: Cost Analysis 1980.

Federal Emergency Management Agency, "National FloodInsurance Program, Final Rule, 44 CFR Parts 59, 60, 61, 64,66 70, 72, and 75," Federal Register , Vol. 50, No. 171(September 4,1985).

Federal Insurance Administration, Guide for Ordinance Development According to 1910.3(e) of the National Flood Insurance Program Regulations , HUD-481-5-FIA,Community Assistance Series No. 1(e) (U.S. Department ofHousing and Urban Development, June 1978).

Federal Insurance Administration, Manual for the Construction of Residential Basements in Non Coastal Flood Environs ,Contract No. H-3849 (1977).

Herbert, Paul J., "North Atlantic Tropical Cyclones, 1979," NOAA’s Climatological Data, National Summary , Volume32, Nos. 1-12, National Oceanic and AtmosphericAdministration, National Hurricane Center, Miami(National Climatic Center, Asheville, North Carolina; 1980).

Houston, James R., Robert D. Carver, and Dennis G. Markle, Tsunami-Wave Elevation Frequency of Occurrence for the Hawaiian Islands , Technical Report H-77- 16 (U.S.Army Corps of Engineers, Pacific Ocean Division; August1977).

Bibliography I-3

Institute of Behavioral Science, Natural Hazard Management in Coastal Areas , NTIS #PB-266 #015(NOAA-Office of Coastal Zone Management, ColoradoUniversity; November 1976).

International Conference of Building Officials, Uniform Building Code Standards (Whittier, California; 1982).

King, C.A.M., Beaches and Coasts (St. Martin's Press, NewYork; 1972).

King, Paul A., and Joseph Millison (eds), National Con struction Estimator, 1 985 , 33rd Edition (Craftsman Book Company,Carlsbad, California).

Komar, P.D., Beach Processes and Sedimentation (Prentice-Hall, Englewood Cliffs, New Jersey; 1976).

Lawrence, Miles B., "North Atlantic Tropical Cyclones, 1978," NOAA's Climatological Data, N ational Summary , Volume29, No. 13, National Hurricane Center, Miami (1978).

"Living with the Shore," book series--see Pilkey and Neal(eds).

Loomis, Harold G., The Tsunami Wave Runup Heights in Hawaii (NOAA/University of Hawaii, Joint TsunamiResearch Effort; May 1976).

Masonry Institute of America, Masonry Design Manual ,Publication 601 (Los Angeles, 1979).

McHarg, Ian, "Best Shore Protection: Nature's Own Dunes," Civil Engineering , Vol. 42, No. 9 (September 1972).

Robert Snow Means Company, Inc., Residential/Light Commercial Cost Data, 1985 , 4th Annual Edition Kingston,Massachusetts; 1985).

Robert Snow Means Company, Inc., Building Construction Cost Data, 1985 , 43rd Annual Edition (Kingston,Massachusetts; 1985).

National Climatic Data Center, Storm Data , Vol. 23, 24, and25, No. 12, National Oceanic and AtmosphericAdministration (Asheville, North Carolina; December1981,1982, and 1983).

National Forest Products Association, National Design Specification for Wood Construction: Stru ctural Lumber, Glued Laminated Timber, Timber Pilings, Fastenings ,(Washington, D.C.; 1982).

National Forest Products Association, Design Values for Wood Construction (Supplement to the 1982 Edition of National Design Specification for Wood Construction ) (Washington,D.C.; March 1982).

North Carolina Building Inspectors' Association, North Carolina Uniform Residential Building Code, North Carolina State Building Code Volume l-B--Residential , adopted byNorth Carolina Building Code Council (1976).

Pararas-Carayannis, George, World Data Center--A Tsunami: Catalog of Tsunamis in the Hawaiian Islands (U.S. Department of Commerce, May 1969).

Patterson, Donald, Pole Building Design , Sixth EditionAmerican Wood-Preservers' Institute, 1969; reprintedApril 1981).

I-4 Coastal Construction Manual

Patterson, James C., "Construction Costs in Coastal HighHazard Areas," Coastal Residential Construction Workshop , Federal Emergency Management Agency(1984).

Pelissier, Joseph M., and Miles B. Lawrence, "North AtlanticTropical Cyclones, 1980," NOAA's Climatological Data, National Summary (National Hurricane Center, Miami;1980).

Pilkey, Orrin H., Jr., and William J. Neal, Series Editors, "Livingwith the Shore" (book series) (Duke University Press,Durham, North Carolina).

Pilkey, Orrin H., Sr., Walter D. Pilkey, Orrin H. Pilkey, Jr., andWilliam J. Neal, Coastal Design: A Guide for Builders, Planners, and Home Owners (Van Nostrand ReinholdCompany Inc., 1983).

Rogers, Spencer M., Jr., "Wooden Wind Anchors far Hurricane-Resistant Construction Near the Ocean," Blue prints , UNCSea Grant, UNC-SG-BP-84-3 (Kure Beach, North Carolina;1984).

Rogers, Spencer M., Jr., "Hurricane Diana: Impact on CoastalDevelopment," Proceedings of Coastal Zone '85, Vol. II,American Society of Civil Engineers (New York, New York;1985a).

Rogers, Spencer M., Jr., "Corrosion in Salt Air," Blueprints ,UNC Sea Grant, UNC-SG-BP-85-3 (Kure Beach, NorthCarolina; 1985b).

Rogers, Spencer M., Jr., Peter R. Sparks, and Katharine M.Sparks, "A Study of the Effectiveness of Building Legislationin Improving the Wind Resistance of Residential Structures," Proceedings of the Fifth U.S. National Conference on Wind Engineering , Texas

Tech University (Lubbock, Texas; November 6-8, 85).

Saffir, Herbert S., Design Construction Requirements for Hurricane-Resistant Construction , American Society of CivilEngineers Preprint 2830 (New York, 1977).

Saffir, Herbert S., "Hurricane Exposes Structural Flaws," Civil Engineering , Vol. 41, No. 2 (February 1971).

Sherman, Zachary, "Tornado Design," AE Concepts in Wood Design (January/February 1977).

Simpson, R. H., and M. B. Lawrence, "Atlantic HurricaneFrequencies Along the U.S. Coastline," TechnicalMemorandum NWS TM SR-58 (NOAA, June 1971).

Southern Building Code Congress International, Inc., Standard Building Code (1982 Edition).

Southern Forest Products Association, How to Build Storm Resistant Structures , Publication No. 121 (New Orleans).

Structural Engineers Association of Hawaii, A Surv ey of Major Structural Damage Caused by Hurricane Iwa, November 23, 1982 (Honolulu, May 1983).

Terrell, T. T., Physical Regionalization of Coastal Ecosystems of the United States and its Territories , FWS/OBS-78/80,U.S. Department of Interior, Fish, and Wildlife Service,Coastal Ecosystems Project 1979)

Texas Coastal and Marine Council, Model Minimum Hurricane Resistant Building Standards for the Texas Gulf Coast(September 1976; Third Printing, June 1981).

Bibliography I-5

University of North Carolina, Sea Grant, Wood in Marine Structures: Proceedings of a Seminar , Sea GrantPublication No. UNC-SG-77-12 (Sponsored by NOAA,Office of Sea Grants, and North Carolina Department ofAdministration (Kure Beach, North Carolina; September1977).

U.S. Department of the Army, Corps of Engineers, Low-Cost Shore Protection--A Guide far Engineers and Contractors (1981).

U.S. Department of the Army, Carps of Engineers, Low-Cast Shore Protection--A Guide for Local Government Officials (1981).

U.S. Department of the Army, Corps of Engineers, Low-Cost Shore Protection--A Property Owner's Guide (1981).

U.S. Department of the Army, Corps of Engineers, Shore Protection Manual (two volumes), Waterways ExperimentStation, Coastal Engineering Research Center (1984).

U.S. Department of the Army, Corps of Engineers, Guidelines for Identifying Coastal High Hazard Zones , GalvestonDistrict (June 1975).

U.S. Department of the Army, Corps of Engineers, Tsunami Wave Elevation Frequency of Occurrence far the Hawaiian Islands , Technical Report H-77-16, Pacific Ocean Division(August 1977).

Walton, Todd L., Jr., Hurricane-Resistant Construction for Homes , MAP- 16 (Florida Cooperative Extension ,ServiceMarine Advisory Program, A Florida Sea Grant Publication;reprinted and revised January 1983).

Walton, Todd L., Jr., and Thomas C. Skinner, Beach Dune Walkover Structures , SUSF-SG-76-006 (FloridaCooperative Extension Service, Marine AdvisoryProgram, A Florida Sea Grant Publication; December1976).

Ward, D.B., Wind-Resistant Design C oncepts for Residences ,Defense Civil Preparedness Agency, Report TR-83 (U.S.Department of Defense, 1976).

∗ U. S. GOVERNMENT PRINTING OFFICE 1986 620-214;40619

Coastal Construction Manual

Documents

Transcript of Coastal Construction Manual