Sink or float?

Norman F. Jacobs Jr., CSI Emeritus, CPE, AACE, ASPE, IIE, PMI, SAR
One of the most important, and least understood, aspects of project management is the ‘float.’ Generally thought of as extra time or leeway for completing work, its use remains controversial, with some arguing the calculations involved are fraught with deception. At stake in the float debate are hundreds of millions of dollars lost or won in timely completions or delays.

In our current era of construction cooperation, sharing project float between the contractor and owner is ‘in,’ while exclusive float ownership by either party is ‘out.’ The calculation process to determine the variability of this float is arithmetically precise, but the data used is a collection of estimates, guesses, simplifications, and assumptions. Once created, the float itself is ephemeral and destroyed by the effluxion of time (i.e. there is no float on completed activities). Similarly, float cannot be bought, sold, stored, or transferred—it only exists as a result of an arithmetic calculation on some future activities in a schedule, and any changes during project execution can have dramatic effect on the overall schedule and all its embedded float values.

Sharing float is rarely clear in case law regarding contracts, and it harms contractors in significant ways. By depriving contractors of use and control of the schedule they create and execute in carrying out the work, this sharing cuts the connection between risk, responsibility, and control. If timely completion resides in the contractor’s domain, then so should control of this time.

Float can lead to other problems. For example, it has been described as the period between the earliest possible start time for an activity not on the critical path and the latest time the activity can possibly finish, minus the actual number of days to do the work.

The project manager must know the consequences of consuming float. On the one hand, it unquestionably provides a contingency within the schedule to offset problems and delays, but any reduction in float increases the risk of project overrunning. As more paths through a schedule approach criticality, there is an increased likelihood a delay on any of the near-critical paths will cause the project to finish late

Gaming and manipulating float is a common worry of some construction people. Any gamesmanship up-front, if even possible, will likely yield unintended consequences to the project’s CPM schedule.

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