Total float, free float and negative float

Total float is shared along a chain. Free float belongs to one activity alone.

That difference decides who you have to ring before you use it. If an activity has 12 days of free float, you can absorb 12 days without speaking to anyone downstream. If it has 12 days of total float and no free float, those 12 days belong to every activity behind it on the same path, and the first person to spend them takes them from everybody else.

Two passes over the network.

The forward pass runs left to right and produces the early dates — the soonest each activity can happen given its predecessors. The backward pass runs right to left from the project finish and produces the late dates — the latest each activity can happen without pushing that finish.

Total float is the gap between them. Where the two passes meet with no gap, float is zero and the activity is on the critical chain.

Three things distort this, and all three are common:

• Calendars. Float is expressed in working days on the activity's own calendar. Twelve days of float on a six-day calendar and twelve days on a five-day calendar are not the same amount of time, and a report that lists both in one column is comparing two different units.
• Constraints. A finish-on-or-before constraint pulls the late dates backwards for everything feeding it. Float upstream drops, sometimes below zero, without a single activity having slipped.
• Multiple finish points. If the project has sectional completion dates, each section drives its own backward pass. Total float against section two says nothing about the overall completion date.

Because genuine slack of two months is rare, and a missing successor produces exactly the same symptom.

An activity with no successor inherits the project's late finish. Its late dates jump to the end of the programme, its total float becomes enormous, and it disappears from every critical path report. The number looks like comfort. It is an open end. That failure is covered in full on the open ends page.

DCMA check 6 flags any programme where more than 5 percent of activities carry more than 44 working days of total float. The threshold is arbitrary. The diagnosis behind it is not.

When you see a cluster of high-float activities, work through them in this order:

1. Does the activity have a successor at all?
2. Does it have a finish successor, or only a start-to-start link — which leaves the finish dangling?
3. Is the successor the right one, or a convenience link to the completion milestone?
4. Is it on a different calendar from the work around it?
5. Only then: is the float real?

Real high float exists. Early enabling works, long-lead procurement with a comfortable required-on-site date, a standalone temporary facility. When it is real, say so in the narrative. Unexplained high float is read by a reviewer as carelessness, and by a claims consultant as an opportunity.

That two things you have entered disagree with each other.

Negative float is never a software error. It means the logic says the work needs more time than the date it has been given. Something has to give, and the programme is refusing to pretend otherwise.

Three causes, in the order you should check them:

DCMA check 7 sets the threshold at zero activities. That is one of the few thresholds worth taking literally in a live update, because negative float carried for months is a signal that the programme has stopped being managed.

This is where the theory meets the contract, and it is worth being precise because the answer is frequently asserted with more confidence than it deserves.

Most standard forms used across the Gulf are silent on float ownership. Where the contract says nothing, the widely followed position — set out in the Society of Construction Law Delay and Disruption Protocol — is that float is not reserved for either party's exclusive benefit. In practice this operates as first come, first served: whichever party's delay reaches the activity first consumes the float, and an employer delay that only eats into float typically produces no extension of time, because completion has not moved.

Two consequences follow.

If you are the Main Contractor, float you build in quietly is float the Employer may use for free. If you are assessing an extension of time claim, the question is not whether an event caused delay to an activity. It is whether it caused delay to completion.

Both of these are contract-specific. Check your own conditions and any programme clause before relying on either.

Run the Schedule Health Check and this page explains two of its results.

• Check 6 — high float. More than 5 percent of activities carrying over 44 days. Read it as a logic completeness test, not a slack measurement.
• Check 7 — negative float. Any activity below zero. Read it as a disagreement between your logic and a date, and resolve the disagreement rather than the symptom.