The Critical Path Method (CPM) - Construction Project Scheduling and Control - page 47

STEPS REQUIRED TO SCHEDULE A PROJECT
For the planning, execution, and completion of a project, many steps are required
that may not be part of scheduling. In this chapter, we discuss the role of the sched-
uler, given that the project has been defined (and designed in most cases). Some
schedules (especially those for fast-track projects , in which construction starts before
design finishes) may include design and design review activities as part of the schedule.
In general, the preparation of a CPM schedule includes the following four steps:
1. Break down the project into work activities
Any project, no matter how large or small, must be divided into smaller entities, called
activities ,or tasks . 1 An activity is a unique, definable element of work. In this step,
there is no absolutely correct or incorrect way to break down the project into work
activities. You may give the same project to 10 schedulers, and they may devise 10 dif-
ferent breakdowns, with some breakdowns being significantly different. In this regard,
there are two schools of thought:
a. Restrict the number of activities for the simplicity of the project schedule :Inthis
case, activities become “major” components. However, there is a practical—and
sometimes contractual—limit on how large an activity can be. For instance, it is
impractical to have Concrete Operations as one activity with 300 days' duration.
In addition, in many contracts, a maximum limit is set on the duration of any
activity, usually about 14 to 30 days.
b. Break the project down into smaller activities : This approach will result in a large
number of activities. The main advantage of this approach is better control of
the schedule during execution. You can easily tell the status (percent complete)
of a minor activity, such as Place Concrete for Spread Footings No. 23, bet-
ter and more objectively than you can for a major activity, such as Building
Foundation. The main disadvantage of having too many activities is the addi-
tional administrative work involved. However, this disadvantage may not be as
important with the use of computers. Furthermore, you can roll up a group of
activities into a major activity, as discussed in Chapter 3.
Factors that should be considered in breaking down the project into individual
activities for better control are the following:
1. Nature of the work/homogeneity : If the work involves two different materials
and/or is measured by different units, it must be divided into two differ-
ent activities. For example, wall construction involves framing, drywall, and
paintingas basic different activities.
1 In reality, the two terms are synonymous. Some software packages use the term task, while others use
activity , sometimes with the term task to indicate a subactivity.