The Critical Path Method (CPM) - Construction Project Scheduling and Control - page 70

Interfering float and independent float are not used in construction scheduling
or even calculated by commercially available software-scheduling programs. They are
sometimes used, although rarely, in delay-claims resolution.

Float Check

When you are calculating float, of any type, it is important to apply educated common
sense to the results, since some computer software programs use their own concepts
and/or assumptions. For example:

• If you are calculating the total float of an activity and find it to be 10 days, try to
delay this activity by that amount and see if the project completion date will be
impacted. If not, increase the delay by 1 day and recheck the project completion
date. It must show a delay of 1 day.
• If you are calculating the free float of an activity and find it to be 5 days, for
example, try to delay this activity by that amount and see if the early start (ES)
of the successor(s) has been impacted. If not, add 1 more day and make sure
the ES of any successor is affected.
• If you are calculating the independent float of an activity and find it to be 3 days,
apply the previous argument (for free float) to make sure using this amount of
float won't impact the ES of any successor and then delay its predecessors by
the maximum total float they have. This delay should not decrease the amount
of the independent float this activity has.

Remember always that TF FF Ind . F.

≥ ≥

Tip Box 4.11

The most important question is: “Who owns the float?” Start with reading the
scheduling-related clauses in the contract.

Node Format

Since each activity has several data items, schedulers have been creative in depicting
these data items inside the activity node. In the examples in this topic, the author
follows a simple node format in which the box contains the activity ID and original
duration. The early dates are placed above the box, and the late dates are placed below
the box. Whether we are drawing the CPM network manually or by using a computer,
we can use one of many node formats or devise our own format. This is a matter
of personal preference; there is no correct or incorrect format. Oracle Primavera P6
and MS Project provide ways to customize nodes. Two examples of node formats are
shown in Figure 4.9.