Scheduling as Part of the Project Management Effort - Construction Project Scheduling and Control - page 275

a contractor is chosen, the contractor will submit a detailed construction schedule
that should fit within the time frame of that single bar. This detailed schedule is then
integrated into the original schedule created by the designer and replaces the single
construction activity.
Summary schedules may also be used for speed, rather than a lack of detailed
information. This approach is not generally used, and such schedules may not be used
for field implementation or project control. This approach is also similar to using
approximate cost estimates when the contractor needs to give the potential client a
ballpark cost estimate of the project without spending much time studying the design
drawings and specifications.
When the design is finalized, the detailed cost estimating and scheduling can
be performed. This practice is used in the traditional delivery method, in which the
project is completely designed and then a contractor is selected through the process
of bidding or negotiation. In other delivery methods, a contractor may be selected 6
before the design is completed or even started, such as in design-build (D/B) or pure
agency construction management (Pure CM or CM Agency) delivery methods. In
this case, the design may come in stages, called design development (DD) . Each
stage specifies a completed percentage of the design. For example, if the design is
called DD30, it is approximately 30% complete. In this case, when the contractor
estimates the cost and duration of the project, the contractor must use the available
design information, and then supplement it with assumptions. Doing so is exactly
like solving a 100-piece puzzle with 30 given pieces and the rest imagined. Later, the
designer provides a more detailed design (e.g., DD60, DD90, etc.). The design is still
incomplete but contains more information than in the previous stage. The contractor
refines the cost estimate and schedule by replacing some assumptions with new design
information. If the project schedule changes, the cost estimate may be affected. If
the scope changes, both the cost estimate and the schedule may change. This process
continues until the final design is issued. The final design 7 willbethebaseforthe
contractor's final cost estimate and schedule.
Estimate-Generated Schedules
Some cost-estimating software programs can export such information as a project's
breakdown to scheduling programs. In most cases, the result is a list of activities along
with their durations but without any logical links (relationships). Before we discuss
the estimate-generated schedule, let us briefly discuss how information is generated
in cost-estimating programs. In short, with regard to labor and equipment costs, two
methods for building the cost-estimating database are used:
6 In some contractual arrangements, there is no prime or general contractor. Instead, subcontractors may
contract directly with the owner (e.g., CM Agency which is CM not-at-risk) or with the construction
management professional (e.g., CM at-risk).
7 In the traditional delivery method, the final design is called the construction document and becomes part of
the contract.