Chapter 32 Floor Systems and Foundation Support. 2 Links for Chapter 32 Slab Construction...

Chapter 32

Floor Systems and Foundation Support

2

Links for Chapter 32

Slab Construction

Reinforcing Concrete

Crawl Spaces

3

Slab Construction

• Most foundation floors are concrete slabs– Usually 5” or 6” thick

– Does not support walls

– Poured as an extension of the foundation wall and footing

SIDE VIEW

SEISMIC CONDITIONS.ON THE SOIL TYPE ANDBE REQUIRED DEPENDINGREINFORCEMENT MAY

PLAN VIEW

TO RESIST CRACKINGOPTIONAL WIRE MESH

4

Slab Construction

• Slab joints help control natural expansion and shrinkage of concrete slabs– Control joints are cut 6-8 hours after concrete is

poured to be sure cracking occurs along the cut– Isolation joints separate a slab from another

slab, wall, column or other structural part– Construction joints are made to support the joint

between two slabs

5

Slab Construction

JOINTCONTROL

JOINTCONSTRUCTIONISOLATION

JOINT

6

Slab Construction

• Slabs are placed above, below, or at grade level– Above grade slabs are indicated with a note

– Below grade slabs are used in basements

– At grade level slabs must be at least 8” above the grade to keep away from moisture

7

Slab Construction

• Slabs are poured after the footings have been set

• At least 4” of sand or gravel fill is placed under the slab

• Slab fill is given as a note on the plans

8


• To help resist cracking, welded wire fabric is placed in the slab and noted as:– 6 X 12—W16 X W8

• 6 = longitudinal wire spacing• 12 = transverse wire spacing• 16 = longitudinal wire size• 8 = transverse wire size

9


• To help resist cracking, welded wire fabric is placed in the slab and noted as:– 6 X 12—W16 X W8

• W indicates smooth wire• D represents deformed wire

10


2 x 12 SOLID BLOCK ( D.F.P.T.)

4 x 4 D.F.P.T. SILL W/

111

1'-10" 8" 1'-0"

3"3"

3" CLR.

6" MIN.SOIL COVER

12"

2"

2 x 12 D.F.P.T. F.J. @ 12" O.C.

5" CONC. SLAB DRIVEWAY APPROACHON 5" COMP CRUSHED ROCK ONROLLED SUBGRADE

3/4" DIA. A.B. @ 24" O.C.

A-35 EA.SIDE OFEA. JST.

COMPACTED1" MINUS ROCK

4" DIA. DRAIN IN 1" MINUS WRAPPED IN FILTER FABRIC

#4DIA x 3'-0" @ 12"O.C.

#4 @ 12" O.C.

3'-6"

5" CONC . SLAB W/ #4 D IA @12" O.C EA. WA Y CENTERED IN SLAB OV ER 55# FELT AND 3/4" PLY.

8 x 36STEEL PILE

4 x 4 STEELBRACE BTWN.PILES. SEEFND. PLAN

TS 6 x 6 x 1/4 STEEL COL.

W 16 x 40

3 x 6 DFPTSILL

3/4" ROD

11

Reinforcing Concrete• To resist expansive soil, steel reinforcing bars

are added to the slab– A 3” minimum coverage is needed if concrete

is exposed to earth– A 2” minimum coverage is needed in

basements– A 1 1/2” coverage is needed when concrete is

not exposed to earth

12


• Post-tensioning is used when concrete is poured on unstable soil

• Steel tendons are placed in the concrete as it is poured

• About 3 to 10 days later the tendons are stretched creating an internal compressive force that helps the concrete resist cracking

13


• Flat slab and ribbed slab are most common forms of post-tensioned concrete– Flat slab tendons range from 3/8” to 1/2” and

are spaced 5’-0” to 9’-0” apart

– A ribbed slab uses ribs or beams under the slab to reduce the span of the slab over the soil and increase support

14


4" CONCRETE SLAB OVER.006 PLASTIC VAPOR BARRIEROVER 1" SAND FILL OVER 4"GRAVEL BASE.

7/16" DIA. x 270k TENDON @ 7'-0" O.C. 2" UP FROM BOTTOM OF SLAB.

115

152

PLASTIC HIGH CHAIR

TENDON-SPECIFY DIAMETER, STRENGTH AND DEPTH.

ANCHOR- SPECIFY DEPTH AND COVERAGE.

15


• Slabs are placed on 6 mil polyethylene sheet plastic to protect against ground moisture

• Depending on the climate, additional rigid insulation is added under the slab

• Plumbing and heating components are placed under the slab

16


1'-6UNDER SLAB4" X 12" DUCT

REG.12" X 6" HT.

17


• Dimensions are added to these components– Outline of slab

– Interior footing locations

– Changes in floor level

– Floor drains

– Exterior footing locations

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Crawl Spaces

• Crawl spaces are at least 18” from bottom of floor and 12” from bottom of joists

• Floor joists span the foundation walls– Usually build from 2 X 6 to 2 X 12 or from

engineered lumber

– Nailed to pressure-treated sill plate or flush to the sill plate

19

Crawl Spaces6" X 12"

6"

VAPOR BARRIERCOVERED W/ .006 BLACK18" MIN. CRAWL SPACE

SHIELD @ WALL / PL. INTERSECTION.PROVIDE METAL TERMITE

4 X 10 D.F.L. GIRDERON 4 X 4 POST ( 4X6@ SPLICE) ON 55# FELT & 30" DIA. CONC. PIERS.

2 X 6 D.F.P.T. SILL W/1/2" x 10" A.B. @ 6'-0" O.C.MAX. 7" MIN INTO CONC.W/ 2" DIA. WASHERS.

1/2" AIR SPACE @ENDS AND SIDES W/ 55# FELT. PROVIDE3" MIN. BEAR.

18" X 6"SCREENEDCLOSABLEVENT @ 10'O.C. 3' MAXFROM EA.CORNER.

30" X 18" MIN.COVERD CRAWLACCESS.

LINE OF FLOORABOVE

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Crawl Spaces• A plywood subfloor is placed

on the joists• Girders are used if the joist

span distance is too great and are supported by a pier

4 x 4 POST & 55# FELT ON18" DIA. x 8" DP. CONC. PIER TYP.

4 x 8 GIRDER W/ GUSSET ON

3" MIN. BEARING W/ 1/2" CLR.ALL SIDES. WRA P W/ 55# FELT

ALL SIDES. WRA P W/ 55# FELT3" MIN. BEARING W/ 1/2" CLR.

4 x 4 POST & 55# FELT ON18" DIA. x 8" DP. CONC. PIER TYP.

4 x 8 GIRDER W/ GUSSET ON

21

Crawl Spaces

CONCRETE BLOCKSTEM WALL

POURED CONCRETESTEM WALL

CONCRETE / JOISTCONNECTION

CANTILIVEREDFLOOR JOIST

GIRDER

JACK STUDS

FLOOR JOIST

FLOOR JOIST

INTERIOR FLOORCHANGE

PIER POST ON55 # FELT

55 # FELTPOST ON

INTERIOR SUPPORT

PIER

FLOOR JOIST

GIRDER

SOLID BLOCK

STEEL DOWEL

FLOOR JOISTFLOOR JOIST

FLOOR JOIST FLOOR JOIST FLOOR JOIST

SOLID BLOCK

INTERIOR SUPPORTW/ METAL POST BASEW/ STEEL ROD


METAL FLASHING

FILL MATERIAL

SOLID BLOCKFLOOR JOIST

PIER

GIRDER

55 # FELTPOST ON

W/ MTL. CONNECTOR





GIRDER

JACK STUDS

FLOOR JOIST

FLOOR JOIST



55 # FELTPOST ON

INTERIOR SUPPORT

PIER

FLOOR JOIST

GIRDER

SOLID BLOCK

STEEL DOWEL



SOLID BLOCK



METAL FLASHING

FILL MATERIAL


PIER

GIRDER

55 # FELTPOST ON

W/ MTL. CONNECTOR

22

Crawl SpacesCONCRETE BLOCK

STEM WALLPOURED CONCRETE

STEM WALL



GIRDER

JACK STUDS

FLOOR JOIST

FLOOR JOIST



55 # FELTPOST ON

INTERIOR SUPPORT

PIER

FLOOR JOIST

GIRDER

SOLID BLOCK

STEEL DOWEL



SOLID BLOCK



METAL FLASHING

FILL MATERIAL


PIER

GIRDER

55 # FELTPOST ON

W/ MTL. CONNECTOR





GIRDER

JACK STUDS

FLOOR JOIST

FLOOR JOIST



55 # FELTPOST ON

INTERIOR SUPPORT

PIER

FLOOR JOIST

GIRDER

SOLID BLOCK

STEEL DOWEL



SOLID BLOCK



METAL FLASHING

FILL MATERIAL


PIER

GIRDER

55 # FELTPOST ON

W/ MTL. CONNECTOR

23

Crawl Spaces• Beams are used instead of joists in post-and-

beam construction• The subfloor is made of 2 X 6 T & G boards or

1 1/8” plywood• Subfloor is glued to the beams• Beams are supported by posts if span is too

great

24

CrawlSpaces

CONCRETE BLOCK STEMWALL

POURED CONCRETE STEMWALL

GIRDER

JACK STUDS

INTERIOR FLOOR CHANGE

PIER POST ON55 # FEL55 # FELT

POST ON

INTERIOR SUPPORT

PIER

GIRDER

STEEL DOWEL


GIRDER PARALLEL TO WALL GIRDER PARALLEL TO WALL

GIRDER PERPENDICULAR TOWALL


SPACE CRAWL

SPACE CRAWL

SPACE CRAWL SPACE

CRAWL

25

Crawl Spaces• If the site is

sloped the floor and foundation methods can be combined

LEDGER AND ANCHOR BOLT METAL JOIST

HANGER

FLOORJOIST

NATURAL GRADE

FILL

REINFORCED CONCRETE SLAB

FLOOR JOIST

GIRDER

POST

CONCRETE PIER

Chapter 32 Floor Systems and Foundation Support. 2 Links for Chapter 32 Slab Construction...

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