Skip to main content
Back to Glossary
Scheduling

Lag

In Plain English

A mandatory waiting period built into the schedule between completing one task and starting the next.

Definition

Lag is a scheduled waiting period inserted between the finish (or start) of a predecessor activity and the start (or finish) of a successor activity in a CPM network. It is used to model real-world waiting times such as concrete cure time, approval review periods, or material lead times. Excessive use of lags in a CPM schedule instead of explicit activities is discouraged by scheduling specifications because it obscures actual project logic.

Why It Matters in Bidding

Lags directly affect the calculated project duration and the critical path, so estimators and schedulers must price them as time a crew cannot be productive even though the contract clock keeps running. Specifications often cap or prohibit open-ended lags because hidden cure or review periods can mask logic gaps that surface as delay claims during the job.

Example

A scheduler inserts a 7-day finish-to-start lag after a slab pour so the framing crew is not mobilized until concrete reaches design strength.

Related Terms

PredecessorSuccessorCritical Path Method (CPM)Float

Frequently Asked Questions

Lag is an intentional waiting time you build into the logic between two activities, controlling when the successor can begin. Float is the calculated slack an activity has before it delays the project. Lag is an input you assign; float is an output the network computes from your durations and logic.
Lags hide the reason for a delay inside a relationship rather than showing it as a named activity with resources and accountability. Owners and CPM specifications prefer explicit cure, submittal, or procurement activities so progress is measurable, durations are auditable, and delay analysis during claims stays transparent.
Yes. A lag consumes calendar days within the network, so it pushes successor dates and can extend completion just like an activity duration. Estimators should confirm whether cure periods, agency reviews, or lead times sit on the critical path, since lag there directly drives general conditions cost.

Need more than definitions?

Get AI-powered bid alerts, automated form filling, and proposal drafting.

Start Free Trial

© 2026 ConstructionBids.ai — A LaderaLabs Product