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Schedulingaka: logic diagramaka: precedence diagramaka: PDM

Network Diagram

In Plain English

A flowchart that shows the logical order and dependencies between all project activities.

Definition

A network diagram is a graphical representation of the logical relationships between project activities in a CPM schedule, showing predecessor-successor dependencies and the flow of work from project start to completion. The Activity-on-Node (AON) format is standard in modern scheduling software. Network diagrams are used to perform forward and backward pass calculations to determine early/late dates and float.

Why It Matters in Bidding

During preconstruction and bidding, a network diagram lets the estimator and scheduler validate that the proposed sequence is achievable within the contract duration before a price is committed. It exposes which activities sit on the critical path, where float can absorb sub coordination problems, and how aggressively crews must be loaded, all of which feed general conditions and escalation pricing.

Example

While bidding a 14-month medical office build, the estimator reviews the network diagram and sees that the curtain wall ties directly to a long-lead steel delivery on the critical path, so they add a phased mobilization line and tighten the general conditions duration before submitting.

Related Terms

Critical Path Method (CPM)Critical PathPredecessorSuccessor

Frequently Asked Questions

A network diagram emphasizes logic, showing every predecessor-successor link and how work flows between activities. A Gantt bar chart emphasizes time, plotting activities against a calendar. Most teams build logic in the network first, then present the schedule as a Gantt for owners and subs who want dates at a glance.
It confirms the project can actually be built within the contract duration and reveals the critical path that drives general conditions costs. Spotting tight sequencing, long-lead items, or stacked trades early lets the estimator price escalation, overtime, and phasing risk accurately instead of discovering schedule pressure after award.
The forward pass works start-to-finish to calculate each activity's earliest start and finish dates. The backward pass works finish-to-start to calculate latest dates. Comparing the two yields total float; activities with zero float form the critical path that controls overall completion and any delay-claim analysis.

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