Scheduling as Part of the Project Management Effort - Construction Project Scheduling and Control - page 273

Detailed
Estimate

Approximate
Estimate

Preliminary
design

Final
design

Design Development

Summary
Schedule

Detailed
Schedule

Figure 10.3 Evolution of a schedule and cost estimate for a project

and location of the work item, not its homogeneity. For example, many schedulers
combine the formwork, rebar, and concrete placement for a reinforced concrete item
(e.g., suspended slab) as “FRP Suspended Slab,” even though formwork is measured
by area (or contact area, to be precise), reinforcement is measured by weight, and
concrete mix and placement is measured by volume. There also might be concrete
curing and/or finishing along with them, which are measured differently.
Many construction and software professionals have suggested one project break-
down for both cost estimating and scheduling, and some of them have claimed success
with this method. Still, this matter is far from being settled.
Other interrelationships exist between estimating and scheduling, as is shown in
the following sections.

Evolution of a Cost Estimate and a Schedule for a Project

When a contractor considers a project for bidding or negotiation, he or she needs to
know the cost and the time frame. 5 (See Figure 10.3.) The owner usually specifies
the required finish date of a project in the bid documents and the contract. How-
ever, the contractor must calculate his or her own estimate of the project's duration
to ensure that he or she can meet the owner's stipulated finish date. If the contrac-
tor's schedule does not meet the owner's date, the contractor must either accelerate
(crash/compress) the project to fit it within the given time interval or obtain the
owner's approval to extend the time limit on the project.
Depending on the size and type of the project, as well as the contractual arrange-
ment, the contractor may start with a rough estimate of the schedule (not necessarily a
critical path method, or CPM, schedule, but an educated estimate of the time required
to build the project). The contractor may use his or her previous experience and a “gut
feeling” to estimate the duration of the major components of the project and to build

5 Timeframe does not mean only the duration. It includes the time span during which the project will occur.
For example, a project scheduled to occur during a winter season in Chicago will probably cost more than if it
were built in the summer.