How to Read a Construction Schedule: What Owners Should Be Watching
A construction schedule is not a list of dates. It's a logic network of dependencies—and knowing how to read it is the difference between catching slippage early and discovering it at closeout.
A Schedule Is Not a List of Dates
Most owners receive a construction schedule as a bar chart (Gantt chart) showing activities with start and end dates. What that chart represents is a logic network—a sequence of interdependent activities where the delay of one has downstream consequences for others.
Understanding how to read a schedule means understanding the logic behind the bars, not just the bars themselves.
Critical Path Method (CPM) Basics
The Critical Path Method identifies the longest sequence of dependent activities from project start to project finish. Any delay on the critical path directly delays project completion. Activities not on the critical path have "float"—they can be delayed by some amount without affecting the completion date.
When your contractor reports that an activity is behind schedule, the first question is: is that activity on the critical path? If yes, the completion date is at risk. If no, how much float exists and is there a recovery plan within the float window?
The 3-Week Lookahead
The master schedule is updated monthly. But the operational document that drives day-to-day execution is the 3-week lookahead—a rolling window of planned work for the next three weeks, updated at every weekly OAC meeting.
The lookahead is where schedule accountability lives. Commitments made in the previous week's lookahead are reviewed against actual completion. When an activity didn't happen as planned, the reason is documented and the recovery plan is stated—not glossed over.
If your contractor doesn't maintain a 3-week lookahead, they are managing schedule by feel rather than by system.
Long-Lead Items and Procurement Tracking
The most common source of schedule slippage that surprises owners is long-lead material delivery. Structural steel, mechanical and electrical equipment, specialty glazing, and custom millwork all have lead times that must be tracked independently of the construction schedule.
During preconstruction, long-lead items should be identified and procurement should begin—even before the GMP is locked in some cases. A contractor who waits until construction starts to order long-lead items is working with a schedule that has already slipped before it began.
Questions to Ask at Every OAC Meeting
- —What is the current status of critical path activities?
- —What activities from last week's lookahead were not completed? What is the recovery plan?
- —What long-lead items are at risk and what is their current delivery status?
- —Are there any pending submittals or RFIs that are blocking upcoming activities?
- —Has the projected completion date changed since last meeting?
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