Reasonableness of Float

Given that float is directly related to the logical sequencing of activities and indicates schedule flexibility, management and auditors will question what constitutes a reasonable amount of float for a particular schedule. Activities’ float differs by status period, given the logical sequence of activities in the network and the program’s remaining duration. Therefore, management should not adhere solely to a target float value (for example, maximum 2 working periods) or specific float measure (for example, 10 percent of program duration). Large amounts of float may be justified, given an activity’s place in the flow of work. For example, landscaping or paving in a construction project may slip many more months than pipefitting. Likewise, nonessential activities in a 2-year project may have far more float available than the same activities in a 6-month project.29

In general, total float should be as accurate as possible; it should be evaluated relative to the program’s projected finish date. The remaining activities in the schedule should be sorted by total float, and those values should be assessed for reasonableness. Management should determine whether it makes sense logically that any activity with relatively high float can actually slip that far without affecting the project’s finish date. For instance, management should ask, is it reasonable that an activity with 55 days of total float can actually slip 55 working days before the program’s finish date is affected? Is the manager of that particular activity aware of this float?

A float value of 55 days may make sense for a project that has 4 years of future planning packages, but a 55-day delay would probably be considered implausible in a 6-month project. Total float values that appear to be excessive should be documented to show that the program management team, having already performed an analysis, has agreed that the logic and float for this relevant activity are consistent with the plan. A float value that is not reasonable may result from a break in logic. Significant changes in float potentially indicate that a logic link has been broken or that an out-of-sequence activity has been completed. It may be that neither indicates true project total float.

All activities with negative float should be questioned. Negative float stems from constraining one or more activities or milestones in the network. The constraint should be examined and justified, and the resulting negative float should be evaluated for reasonableness. Management should be aware of activities that are behind schedule with respect to a constrained activity. If a delay is deemed significant, management should develop a plan to examine options for recovering from the schedule slip. If the negative float cannot be mitigated, then the milestone should forecast a slip to eliminate the negative float.

  1. Total float is also tied to the overall confidence level of a schedule, assuming that a schedule risk analysis has been performed. The more optimistic a schedule may be (less confidence in meeting the completion date), the lower the available float is; the more pessimistic a schedule (more confidence in meeting the completion date), the greater the available float.↩︎