Copyright © 2009 T.L. Martin & Associates Inc. Chapter 3 Requirements of a realistic CPM schedule

Copyright © 2009Copyright © 2009T.L. Martin & Associates Inc.T.L. Martin & Associates Inc.

Chapter 3 Chapter 3 Requirements of a realistic Requirements of a realistic

CPM schedule.CPM schedule.


A realistic CPM schedule A realistic CPM schedule

• The owner and its construction representatives need to determine a realistic contract performance period. – Too little time increases initial pricing and will result in contractor

requests for time due to even minor changes. – Too much time (and if the contract disallows an early

completion) initial pricing will be greater than necessary due to extended contractor overhead cost.

• The owner incurs time related costs as delivery of the project is prolonged: – added administrative costs– lost project use costs – lost production cost, facility rent and / or duplicate space costs.





• Forecast completion and key project milestone• Document actual progress• Establish reasonable payment• Predict manpower needs• Determine the impact of changes

The project schedule affects the management effort of the project from the day it is accepted until substantial completion.

If properly prepared, the schedule can:



• Incorrectly forecast completion• Support overpayment• Incorrectly indicate that the owner’s actions

will impact job progress• Incorrectly indicate that the contractor

and/or subcontractor will impact job progress

If improperly prepared, the schedule can:



• Define the individual tasks that make up the project.

• Define how the tasks are related to each other.• The construction schedule should present a

detailed understanding of any contract specified phasing and/or sequences of work.

• Activity identification and associated quantities of work by phase or task sequence should be accurately determined.



• Activity duration should be developed based on quantities of work it represents with an attainable production.– Considering estimate detail, crew make-up and

anticipated man-hours and/or equipment hours per installed unit, the bid estimate represents a good measure of likely performance unique to the contractor.

• Activity logic and duration should include any unique requirements defined by the contract drawings and specification.


Activities Activities • Defines the scope of work

– Drawings– Estimates– Specifications

• Should be based on work quantity• Separate work performed by multiple subcontractors into

separate activities• Owner and contractor / subcontractor should agree to

activity scope and allocated work quantities• Description - 48 characters (P3)• Description - should contain some type of operating verb

to avoid confusion


Planning Unit (Original Duration)Planning Unit (Original Duration)

• PLANNING UNIT: The increment of time used to schedule a project - hours, days, weeks, or months

• Work starts in the morning of the (day) and finishes in the afternoon (P3)

• Duration of zero, work starts in the morning but completes in the afternoon of the previous period (P3)

• Multiple shifts cannot be defined in a work day calendar• Use hours as the planning for multiple shift operations• Maximum suggested duration for work tasks is 30

calendar days (20 work days)


Activity Identifications (“ID”)Activity Identifications (“ID”)

• Alphanumeric values to define activities (individual work scopes)

• Should relate to areas and/or phases of the project• Assign values for “continuous flow from left to right”• Predecessor should always be lower than successor• Leave a gap in sequence• Should not change• Required for “apples to apples” comparisons• Some scheduling software change IDs and/or line

numbers


Type of ActivityType of Activity

• Work Tasks

• Hammock Activities or Summary Bars

• Milestones

• Flags


Activity CodesActivity Codes

Definition - Assigned to an activity to organize them into manageable groups for:•Updating•Reporting•Analyzing•Summarizing


Activity CodesActivity Codes

• Areas of the Project

• Phases

• Work Descriptions - Type of Work

• Responsibility

• Specification Section (CSI)

• Contract Type

• Blank - User defined as needed


CalendarsCalendars• Define work periods when activities can start and

stop• Global calendars - applied to all subsequent (base)

calendars• Project Start sets 1st day of the project in planning

units• Global calendar typically should be left as a seven

day work week with no holidays• Base calendar (31 possible in P3) - typical should be

five day work week with holiday• Specifications should define calendar and holidays


CalendarsCalendars

Other non-work periods:• Winter shut down period• Environmental shut down period• Anticipated lost weather days (sometimes

defined in specification)


Logical RelationshipsLogical Relationships• Relationships logically connect activities• Should represent the contractors proposed sequence of

construction• Either predecessor or successor relationships• Only one activity that has no predecessor – award /

notice to proceed (“NTP”)• Only one activity that has no successor - completion• Four main relationship types:

– Finish to Start– Start to Start– Finish to Finish– Start to Finish


A realistic CPM schedule A realistic CPM schedule • The CPM should be developed following standard

guidelines for useful schedules.– The schedule should depict how the project team

intends to build the job.– The schedule contains one start and one ending

activity. Only one activity in the schedule does not have a predecessor and only one activity does not have a successor.

– The schedule should address all contract requirements.– The use of software constraints to activity timing is

minimal to none.– The use of relationship leads and lags between

activities is held to a minimum to none. – Activities are coded to allow easy report selection.



• Allow adequate time for development review and approval

• Include and/or follow a comprehensive scheduling specifications in contract requirements

• Owners should not issue NTP until an accepted schedule is in place

• Owner should prepare an accurate independent resource and cost estimate for the project.

• Responsibility for preparing the schedule must include contractors field superintendent, subcontractors and Owner representatives.

How to Assure a Quality Schedule


Please continue to Chapter 4Please continue to Chapter 4Standard CPM Smoke and Standard CPM Smoke and

Mirror TricksMirror Tricks(Manipulations)(Manipulations)

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Copyright © 2009 T.L. Martin & Associates Inc. Chapter 3 Requirements of a realistic CPM schedule