Construction Planning and SchedulingConstruction Management Training Program For Technical Departments by AIT Extension & PRMP, Government Of Punjab

Santi Charoenpornpattana, Ph.D.Assistant Professor & Director

Construction Engineering & Management ProgramKing Mongkut’s University of Technology Thonburi

AIT Conference Center18th August 2009

Planning and Scheduling

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Three basic objectives of construction project management

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Cost

Time Performance

What is “Planning” ?

• General: “the function of selecting organization’s

objectives and establishing the policies,

procedures, and programs necessary for achieving

them.

• Project management context: “establishing an

predetermined course of action within a forecasted

environment”

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Planning & Control / Time & Cost

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SchedulingCost

Planning

Schedule Control

Cost Control

Time Cost

Planning

Control

Planning & Control / Time & Cost Tools

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Bar Chart/CPM

Estimation/Cost

Planning

Bar Chart/CPM/

S-CurveEarned Value

Time Cost

Planning

Control

What is “Scheduling”• “the function of arranging and sequencing the

planned activities in order to achieving the objectives”

• Questions to be answered:

1. What is the total duration of the project?

2. What are the start and finish dates for the activities?

3. Can a project activity be delayed? How long?

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Real life example• It’s now 8.30 am.

• You want to know the earliest time you can finish personal task for the lecture today:▫ Take a bath (5 min)

▫ Dress up (5 min)

▫ Boil water for tea (10 min)

▫ Food reheat (5 min)

▫ Eat breakfast (10 min)

▫ Having tea (5 min)

▫ Walk to lecture room (5 min)

• Can you be on time for the class? If not, what should I do?

• What is the earliest time you could reach the class?

• How much free time do you have before the class?

• Can I have any break after each task?

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Planning Process

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DESCRIP

OFWORK

OBJECTIVES

PROJECTORGANIZATIO

N

“WHO DOES WHAT”WORK

PACKAGEDESCRIPTION

WORKBREAKDOWNSTRUCTURE

WORKSCHEDULE

PROJECTOBJECTIVE

S

SCOPE OF WORK

WORK PLAN

SCHEDULE

MANPOWER

BUDGET

“WHAT”

“WHO”

1 2

34

6

7

5

“HOW MUCH”PROJECT

BASE PLAN

“WHEN”

“HOW”

LOGICALSEQUENCE

AND RESOURCE

REQUIREMENTS

Source: lecture note Dr. Chotchai Charoenngam,  CE70.21 Integrated Project Planning and Control School of Engineering and Technology, AIT - 2008

Typical Scheduling techniques

1. Bar Chart

2. Network Diagram

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Categorizing scheduling techniques

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Bar Chart

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Barchart• Henry L. Gantt, World War I -1917

• Classic technique & Well known

Pro:

▫ Easy, Very effective communication tool

▫ Very popular for representation of simpler schedules

▫ Understandable to all level of management

Con:

▫ Can be complex when have >100 activities

▫ Key shortcoming: No dependencies captured

▫ Most effective as reporting format rather than representation

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Bar Chart – construction phase

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dec

jan

feb

mar

ap

ril

may

jun

e

july

Foundation

Structural

Architectural

M & E

Landscape

TIME

ACTIVITIES

Bar Chart – whole development

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Hierarchy of Bar Charts

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Network Diagram

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Network Diagram• Shows not only timing but also interrelations and

dependencies of the activities

• Logical sequence behind the activities are important

• Two main types of network diagram

1. CPM (Critical Path Method)

2. PERT (Program Evaluation Review Technique)Santi Charoenpornpattana, Ph.D. @2009

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A B C

D

EActivity 1 Activity 2 Activity 3

Activity 4 Activity 5

CPM• Standard scheduling technique in construction

industry

• Logical sequence is the key

• Embedded in all commercial scheduling software (MS Project, Primavera Project Planner, etc)

• Very effective for control purpose

• Specified in the contract of almost all medium to large scale projects as a rule especially for the processes of change order and dispute resolution

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Two ways of representing CPM1. Arrow diagramming

2. Precedence diagramming

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1 2 3 4 5 6Mobilizing

Laying outfootings

Excavatingfootings

Formwork &Concrete

Erecting steel

Formwork procurement

Steel procurement

MobilizingLaying out

footingsExcavating

footingsFormwork & concrete

Erecting steel

Steelprocurement

Formworkprocurement

Steps in CPM scheduling

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Identifying activities

Assigning logical interrelationships between activities

Assigning duration for activities

Calculation

1. Identifying activities•Breaking down project’s work into smaller

elements•Work Breakdown Structure (WBS)

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Templates

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Example 1

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WBS of house construction

Example 2

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WBS of large scale building construction

Numbering

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How many level ?•Until the manageable level

•Until there is no important constraints between sub-activities

•For small to medium construction work, 4-5 levels would be appropriate

•For large-scale project, multiple-linked WBS are used. (Master WBS, GC WBS, SC WBS, etc.) Each is done by different party.

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2. Logical interrelationships•Time-sequence relationships among the

various activities▫Mandatory – technical constraint

Foundation before structure Excavation before backfilling

▫Discretionary – management constraint Resource limitation Organization policy/procedure

▫External – external constraint Seasonal condition Law and regulations

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Example

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1 2

4

5 6

3

AB

C

D

EF

A

C

B D

E

F

Arrow diagram

Precedence diagram

dummy arrow

QuizActivity

Excavation

Foundation

Basement

Structure

Wall

Rafter

Flooring

Rough interior

Roof

Finishing

Landscape

Cleaning upSanti Charoenpornpattana, Ph.D. @2009

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Predecessor-

Excavation

Foundation

Foundation, Basement

Structure

Structure , Wall

Structure

Flooring

Rafter

Rough interior, Roof

Basement, Wall

Landscape, Finishing

Answer

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Excav Found

Base

Struc Floor

Wall

Rafter

Landscape

Rough

Roof

Finishing

Clean

Arrow vs Precedence diagramming

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Arrow vs Precedence diagramming

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3. Duration•Amount of time assigned to complete a

particular activity•How to determine?

▫Historical information▫Information from subcontractor▫Handbook

•Duration = Work Quantity

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Crew production rate

4. Calculation

• Forward & Backward calculation• The questions:

1. What is the total duration of the project?2. What are the start and finish dates for

the activities?3. Can a project activity be delayed? How

long?

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Notations

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Duration Total floati j

Early start Early finish

Late start Late finish

Activity description

Activity DescriptionActivity Description

Earlystart

Earlyfinish

Latestart

Latefinish

Duration

Totalfloat

Forward pass

1 2 3 4 5 6 7

A

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3 TF1 2

0 3

LS LF

A

AA

0 3

LS LF

3

TF

BB

3 7

LS LF

4

TF

4 TF37

LF

B

ES EF

ES EF

EF = ES + D

3

LS

Backward pass

1 2 3 4 5 6 7

A

B

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3 TF1 2

0 3

1 3

A

AA

0 3

0 3

3

0

BB

3 7

3 7

4

0

4 TF37

7

B

ES EF

ES EF

LS = LF - D

LF is assigned or obtained

TF = LF – D – ES

3

3

What is “Float”•Float or slack of activity is a measure of

flexibility, or inherent surplus time in the activity’s scheduling

•It indicates how long the activity can be delayed or extended without having effect on completion of the whole (or part) project

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Example analysisActivity Duration Preceding activity

A 2 -

B 2 A

C 4 B

D 1 A

E 2 D

F 2 C,E

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AA0 2

0 2

2

0

BB2 4

2 4

2

0CC

4 8

4 8

4

0

DD2 3

5 6

1

3EE

3 5

6 8

2

3

FF8 10

8 10

2

0

CRITICAL PATH

What the “critical path” can tell?•The path is critical !

•No delay is allowed in the path

•Management must take special care on all activities along the critical path

•Acceleration of the critical activities can shorten total project duration

•Who cause delay !

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QuizActivity Predecessor Duration

Excavation - 2

Foundation Excavation 4

Basement Foundation 4

Structure Foundation, Basement 8

Wall Structure 4

Rafter Structure , Wall 2

Flooring Structure 3

Rough interior Flooring 3

Roof Rafter 2

Finishing Rough interior, Roof 4

Landscape Basement, Wall 8

Cleaning up Landscape, Finishing 2

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Logical relationships• Four logical relationships:

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AAES EF

LS LF

D

BBES EF

LS LF

D

AAES EF

LS LF

D

BBES EF

LS LF

D

AAES EF

LS LF

D

BBES EF

LS LF

D

AAES EF

LS LF

D

BBES EF

LS LF

D

1. Finish-to-Start (FS) 2. Start-to-Start (SS)

3. Finish-to-Finish (FF) 4. Start-to-Finish (SF)

Can start B only when A finished Can start B only when A started

Can finish B only when A finished Can finish B only when A started

Lag•Waiting duration before beginning of the

subsequent action

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AAES EF

LS LF

D

BBES EF

LS LF

D7

AAES EF

LS LF

D

BBES EF

LS LF

D

5

AAES EF

LS LF

D

BBES EF

LS LF

D

2

AAES EF

LS LF

D

BBES EF

LS LF

D

3

Use of SF SS FF and Lag

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Excavation

Concrete

0 1 2 3 4 5 6 7 8

Excav 1Excav 12

Excav 2Excav 24

Conc 1Conc 14

Conc 2Conc 22

Excav Excav 6

ConcConc6

2

2

Excavation takes 6 days Concrete takes 6 days Concrete can be started after

excavation is already started for 2 days Concrete can be finished after

excavation is already finished for 2 days

Calculation of PDM

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AAES EF

LS LF

0

BBES EF

LS LF

3

CCES EF

LS LF

4

DDES EF

LS LF

2

EEES EF

LS LF

2

FFES EF

LS LF

4

GGES EF

LS LF

6

HHES EF

LS LF

6

IIES EF

LS LF

3

JJES EF

LS LF

2

KKES EF

LS LF

0

1

3

2

1

Calculation of PDM

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AA

0

BB3

CC 4

DD2

EE 2

FF4

GG6

HH

6

II3

JJ2

KK0

1

3

2

1

Calculation of PDM

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AA0 0

0 0

0

BB0 3

0 3

3

CC0 4

1 5

4

DD4 6

4 6

2

EE 4 9

7 9

2

FF 4 8

5 9

4

GG6 12

8 14

6

HH 9 15

9 15

6

II12 15

14 17

3

JJ15 17

15 17

2

KK17 17

17 17

0

1

3

2

1

Quiz

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Float

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Float•Measure of flexibility , inherent surplus

time

•Activity’s allowable delay or extended time without causing delay to whole project

•Terminology :

1) Total float

2) Free float

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Definition•Total Float Amount of time that activity can be

delayed without affecting completion of the whole project

•Free Float Amount of time that activity can be

delayed without delaying the early start of following activity

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Total Float•Total Float (TF) = LF-D-ES

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2 53

8E

6 3

4 84

8C

4 0

1 32

6D

5 3

2 42

4B

2 0

2 20

2A

0 0

2 108

10F

8 0

2 4 6 8 10

AB

DC

EF

1 3 5 7 9

Total Float is share by all activities in the path

Free Float

activitycurrent

activityfollowig EF - ES

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• Free Float (FF) =

Free float is not shared

AA0 0

0 0

0

BB0 3

0 3

3

CC0 4

1 5

4

DD4 6

4 6

2

EE 4 9

7 9

2

FF 4 8

5 9

4

GG6 12

8 14

6

HH 9 15

9 15

6

II12 15

14 17

3

JJ15 17

15 17

2

KK17 17

17 17

0

1

3

2

1

Who own float•Tension between owner and

contractorTension contractor

•Signifiant legal implications

•Problem:

▫Owners seek to push contractors on tight schedule Too many late starts risk overall project

duration

▫Contractors seek flexibility Flexibility has value

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Presentation of schedule

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Questions to ask

•Present to whom?

•Which format ?

•Level of detail?

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CPM

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Bar chart

Bar chart

CPM

Example

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2 53

8E

6 3

4 84

8C

4 0

1 32

6D

5 3

2 42

4B

2 0

2 20

2A

0 0

2 108

10F

8 0

2 4 6 8 10

AB

DC

EF

1 3 5 7 9

Draw Relationship

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2 4 6 8 10

A

B

D

C

E

F

1 3 5 7 9

Delay Claim and Schedule Analysis

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What is “delay”?•Time during which some part of the project

has been extended or not performed due to an unanticipated circumstance

•What causes delay?

•Who involves delay?

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Classification of delay

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Excusable and Non-excusable delays•“Excusable delay” is the one that justified

an extension of the project duration

•Examples of excusable delay?

•“Non-excusable delay” ⇒ extension is not permitted

•How can we know whether the delay is excusable or not? ⇒ “ Contract”

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Examples

• In general conditions of contract:“8.3 Delays and Extensions of Time

8.3.1 If the Contractor is delayed at any time in the progress of the

work by an act or neglect of the Owner or Architect, or of an

employee of either, or of a separate contractor employed by the

Owner, or by changes ordered in the work, or by labor disputes, fire,

unusual delay in deliveries, unavoidable casualties or other causes

beyond the Contractor’s control, or by delay authorized by the

Owner pending arbitration, or by any other causes which the Architect

determines may justify delay, then the Contract Time shall be extended

by Change Order for such reasonable time as the Architect may

determine”

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Source: American Institute of Architect Document A201

“Compensable” and “Non-compensable” delays•Excusable delay

1. Compensable

2. Non-compensable

• If compensable, contractor is entitled to additional compensation (normally money)

• In some cases, compensation without extension of time

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Critical & Non-critical delay•Not all delays result in delay to the whole

project completion

•Critical delay is delay occurred in critical activity, hence it delays the whole project completion

•Excusable but non-critical delay does not justify extension of project duration

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Consequences of excusable delays

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Critical Non-critical

Compensable

Non-compensable

Additional payment and

time extension

Additional payment, but

no time extension

Time extension, but no additional

payment

No time extension, and no

additional payment

How to classify?•Excusable vs Non-excusable

•Critical vs Non-critical

•Compensable vs Non-compensable

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“Contract”

“Schedule analysis”

“Evidence”

Scheduling and delay analysis• Schedules play a very important role in

construction delay claims

• Delay can be identified, defined, and explained by schedules

• Delay of an activity may or may not become delay of the whole project

• Without schedule, difficult to recognize delay

• Objective is to prove Critical or Non-critical delay

• Only delay on critical activity is considered

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Conlucsion•Concept of scheduling•Bar chart•CPM

▫Arrow diagram, PDM▫CPM analysis▫Interpretation

•Float•Presentation of Schedule

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