Float (Programme Float)

Float - also called programme float, schedule float, or slack - is the amount of time a task can be delayed without pushing back the project's overall completion date. It is calculated from the critical path method (CPM) by comparing each task's earliest possible finish date to its latest allowable finish date. Tasks on the critical path have zero float; any delay to those tasks delays the project. Tasks with float can absorb delay up to their float amount before becoming critical.

Total Float vs Free Float

There are two types of float that matter in practice. Total float is the maximum delay a task can absorb without delaying the project end date. Free float is the delay a task can absorb without delaying its immediately following tasks. A task can have 10 days of total float but zero free float - meaning it can slip without affecting overall completion, but not without affecting the next task in sequence.

Near-critical tasks - those with only a few days of float - warrant the same attention as critical-path tasks, because minor disruption quickly converts them to critical.

Float Ownership on Construction Projects

In construction contracts, float ownership is a genuine source of disputes. A contractor may plan their programme with float built in to manage risk. The client and contract administrator sometimes argue that float belongs to the project as a whole. Where the contract is silent on float ownership, it should be addressed explicitly at contract stage to avoid extension-of-time disputes.