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Scheduling

Predecessor

In Plain English

A task that must be completed before the next task can start.

Definition

A predecessor is an activity that must begin or finish before another activity (the successor) can begin or finish, as defined by the logical relationships in a CPM schedule. The four relationship types are Finish-to-Start (FS), Start-to-Start (SS), Finish-to-Finish (FF), and Start-to-Finish (SF). Correct predecessor logic is fundamental to a valid CPM schedule.

Why It Matters in Bidding

Predecessor logic determines what is on the critical path, which directly affects the project duration an estimator prices into general conditions and time-related overhead. Sloppy or missing predecessors produce an unrealistic schedule that understates the time and money needed, exposing the bidder to liquidated damages and cash-flow strain. In delay claims, the defensibility of the schedule turns on whether predecessor relationships reflect how the work actually had to be built.

Example

Building the bid schedule, the estimator sets slab-on-grade as a finish-to-start predecessor to interior framing, so the CPM correctly shows that any concrete delay pushes framing and lengthens the time-related general conditions in the bid.

Related Terms

SuccessorLagCritical Path Method (CPM)Network Diagram

Frequently Asked Questions

Finish-to-Start, where the predecessor must finish before the successor starts, is most common. Start-to-Start ties two activities' starts together, Finish-to-Finish ties their completions, and Start-to-Finish is rare and links a predecessor's start to a successor's finish. Choosing the right type keeps the schedule logic realistic and the critical path accurate.
The critical path is the longest chain of dependent activities with no float, and predecessors define that chain. If a critical predecessor slips, every downstream successor shifts and the completion date moves. Estimators and schedulers use predecessor logic to find which activities drive duration and where added crews or sequencing could shorten the job.
A predecessor is the controlling activity that must start or finish first; the successor is the activity that depends on it and follows according to the relationship type and any lag. Every logical tie has both. Reversing or omitting these links produces open ends that invalidate the schedule and weaken any later delay analysis.

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