Every schedule update ends with a number most owners skim past: float. It is the most useful number in the report and the most misunderstood. Float is not spare time. It is the amount an activity can slip before something else has to move, and once it is spent, it is gone for every activity that shares it.
Total float, free float and the critical path
In a logic-driven schedule, every activity is linked to the work that must come before it and the work that depends on it. From those links the software calculates two kinds of float.
- Total float is how many working days an activity can slip before the project finish date, or a contract milestone, moves.
- Free float is how many days it can slip before the very next activity has to move.
- The critical path is the chain of activities with the least total float. On a healthy schedule that is zero. A delay to any activity on it moves the finish date day for day.
The distinction matters in the field. An activity with ten days of total float but no free float can still delay the next crew tomorrow, even if the finish date does not move. That is the question we ask in every update: what happens to the next crew if today’s work slips?
Float is shared, so it needs an owner
Float does not belong to one trade. If the drywall crew uses five days of float on a floor, the painter, the ceiling installer and the flooring crew behind them have five fewer days. If an owner decision takes three weeks longer than planned, that time comes out of the same pool. On most of our contracts float belongs to the project, and we manage it that way: openly, with every use recorded and explained in the monthly report.
A schedule with plenty of float on paper and none in the field is the most dangerous kind. It looks safe until the week it is not.
Project controls manager, Jacob Wiseman
What we watch in every update
- Float trend, not just float. A path that had 20 days last month and 12 this month is a bigger warning than a path that has held at 5 for a quarter.
- Near-critical paths. Any chain within ten working days of critical gets the same attention as the critical path itself, because one bad week makes it critical.
- Logic, not constraints. Hard-coded dates hide float. We keep constraints to contract milestones and real outside dates, so the float the schedule reports is float that exists.
- Long-lead items. Switchgear, generators, elevators and curtain wall often sit on near-critical paths through procurement. A ship date that slides a week can consume float months before anyone on site notices.
How owners should read it
When you get a schedule update, ask three questions. Which path is critical, and did it change since last month? How much float is left on the next two paths behind it? Which upcoming decisions sit on those paths, and when are they due? If your builder cannot answer those in plain language, the schedule is not doing its job. A deadline is only as strong as the plan behind it, and float is how you measure how strong that plan still is.
