The Critical Path Method (CPM) - Construction Project Scheduling and Control - page 51

WBS
Level

4

AFK-09-6000
Floor Cover, 4th
floor, 8 days

AFK-09-9100
Wall Paint, 4th
floor, 4 days

5

AFK-09-6100
Floor Carpet, 4th
floor, 3 d ays

AFK-09-6200
Floor Ceramic tile,
4th lo o r, 4 days

AFK-09-6300
Floor Marble tile,
4th loo r , 5 days

AFK-09-6400
Hardwood Flooring,
4th floor, , 4 days

AFK-09-9110
Wall Paint, 4th
floor, 4 days

Figure 4.3 Level of confidence forces the breakdown of one activity while another activity
at the same level stays without being broken down further

and then was expanded in 2004 to 50 divisions 2 and was later updated in 2010-2014,
and will keep getting periodic updates.

2. Determine activities' durations

Techniques for estimating activity duration vary from one situation to another,
depending on the type of work, the estimator, and other factors. Most activity
durations can be estimated as follows.
For example, for 10,000 CY (cubic yards) of excavation and a crew that averages
800 CY per day, the following is true:

Duration = 10 , 000 CY∕800 CY per day = 12 . 5 days ≈ 13 days

This information could come from the project team (project manager, project
superintendent), who receives feedback from field crew leaders; from the estimating
department; or from other sources (e.g., subcontractors). It is given to the scheduler
with the project manager's approval. Durations are by no means carved in stone. They
are based on previous experiences, with adjustments made for current job conditions,
such as weather conditions, design complexity, soil type, and so forth. Durations are
also subject to the crew size and the number of crews, if there is more than one crew.
The durations of some activities are totally subjective and left to the project manager
and the technical team, such as the mechanical or electrical repair team, to “guessti-
mate.” Depending on the nature of the work and the work environment, it is a good
idea for the scheduler to be moderately conservative in estimating durations. Remem-
ber that such estimates of durations, even when they have a scientific basis, are future
predictions—and Murphy's Law always exists!

2 Fifteen of the 50 divisions in the CSI MasterFormat 2014 are currently blank and labeled as “Reserved for
future use.” Some construction professionals refer to the count of the CSI MasterFormat 2004 and later
versions as 49 divisions, because they forget to count division 00, Procurement and Contracting
Requirements.