Preconstruction — Scheduling & Phasing

Float (Schedule)

The slack an activity has before its delay starts to push other work or the finish date.

Quick Answer

Float, or slack, is the amount of time an activity can be delayed without affecting a later milestone. Total float is the delay allowed before the project finish date moves; free float is the delay allowed before the next activity is affected. Activities with zero float are on the critical path, so float measures scheduling flexibility.

The Full Picture

Float exists because not every activity is time-critical. When a schedule network is calculated, some activities can start earlier or later within a window without harming the project, and some can't move at all. Float quantifies that flexibility, and it's one of the most useful and most misunderstood numbers a CPM schedule produces.

Mechanically, float comes from the difference between an activity's late dates and early dates after the forward and backward passes. Total float is how long an activity can slip before it delays the project completion. Free float is the narrower figure: how long it can slip before it delays its immediate successor. An activity can have free float of zero but total float of days, or vice versa.

Negative float appears when a schedule is behind: if an imposed deadline or constraint is earlier than the network's calculated dates, activities show negative float, signaling how much time must be recovered to meet the constraint. It's an early-warning number that a target date is at risk.

In practice, float is often contested. Contracts may specify who owns float, since consuming it affects both parties' flexibility. A common dispute is a contractor or owner using up shared float and leaving the other with none. Good schedulers track float trends, not just values, because float being steadily eroded is a leading indicator of trouble even before the finish date formally slips.

Real Examples

→Total vs free float: An underground utilities activity can slip five days before delaying the finish (total float) but only two days before delaying the next activity that depends on it (free float).
→Negative float warning: A contract milestone set earlier than the calculated dates drives ten days of negative float, telling the team it must recover ten days to hit the deadline.
→Float ownership dispute: A subcontractor's early delivery consumes the shared float on a scope, leaving the GC no slack, prompting a review of who the contract says owns float.

Common Misconceptions

People assume: Float is spare time that belongs to the contractor.

Actually: Ownership of float depends on the contract, and float is often a shared project resource. Assuming it's automatically yours to consume is a frequent source of scheduling disputes when the other party needed it too.

People assume: Total float and free float are the same thing.

Actually: Total float is slack before the project finish moves; free float is slack before the very next activity is affected. Free float is always less than or equal to total float, and confusing them leads to bad sequencing calls.

Does MeltPlan Solve This?

Not directly

Not directly. Float is calculated and managed inside a CPM schedule, and scheduling is outside MeltPlan's scope. MeltPlan focuses on preconstruction document and estimating work such as drawing review, takeoff, and bid leveling. To calculate total and free float you'll want a dedicated CPM scheduling tool like Primavera P6 or Microsoft Project.

Frequently Asked Questions

What is the difference between total float and free float?

Total float is how long an activity can be delayed without pushing the project finish date. Free float is how long it can be delayed without affecting the very next activity. Free float is always less than or equal to total float.

What does negative float mean?

Negative float means the schedule is projecting to miss an imposed deadline or constraint. The magnitude shows how much time must be recovered, through acceleration or resequencing, to meet the target date.

How is float related to the critical path?

Critical path activities have zero float, meaning any delay to them delays the project. Float measures how far a non-critical activity can move before it becomes critical or affects other work.

Who owns the float in a construction schedule?

It depends on the contract. Some contracts assign float to the project as a shared resource, others to a specific party. Because consuming float reduces everyone's flexibility, ownership is a common source of scheduling disputes.

Related Terms

Critical PathThe chain of dependent activities whose total length determines the project finish date.CPM ScheduleA logic-linked schedule that calculates which chain of activities controls the finish date.Baseline ScheduleThe approved, frozen version of the schedule that progress is measured against for the life of the job.Schedule CompressionShortening a project's duration without reducing scope, by crashing or fast-tracking the work.Look-Ahead ScheduleA short-window, detailed plan of the next few weeks of field work, pulled from the master schedule.Master ScheduleThe top-level, whole-project timeline of major phases and milestones from design to closeout.

More Preconstruction — Scheduling & Phasing Terms

Sources

  1. Project Management Institute (PMI) — Practice Standard for Scheduling
  2. AACE International — Planning & Scheduling Recommended Practices
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