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Scheduling

Milestone

In Plain English

A key date in the project schedule marking the completion of a major phase or deliverable.

Definition

A milestone is a significant event or point in the project schedule with zero duration that marks the completion of a major deliverable or phase, such as permit issuance, structural steel completion, building enclosure, or substantial completion. Milestone dates are often contractually required and may trigger liquidated damages if missed. They are used to monitor overall project progress at summary level.

Why It Matters in Bidding

Milestones anchor the contractual schedule that owners use to gauge progress and that may carry liquidated damages, so estimators and schedulers must align bid durations and crew loading with each required date. Interim milestones also govern progress payments and tie-ins with other prime contractors, making a missed milestone a cash-flow and claim event, not just a planning slip.

Example

The schedule baseline included a 'building dried-in' milestone that triggered the owner's interior-finishes release, so the GC sequenced roofing and exterior framing to hit that date and protect downstream subs' starts.

Related Terms

Baseline ScheduleCritical PathGantt ChartNotice to Proceed

Frequently Asked Questions

A milestone has zero duration and consumes no resources; it simply marks that an event has occurred, such as permit issuance or substantial completion. A regular activity has duration, resources, and cost. Milestones are used to track and report major checkpoints and often serve as contractual deadlines tied to damages or payments.
Yes, when the contract assigns liquidated damages to specific interim or final milestones rather than only to overall completion. Estimators and schedulers should identify which milestones carry damages, confirm the daily rate, and build in enough float, since interim-milestone LDs can accrue even if the project finishes on time.
Map each contractual milestone to the activities that drive it, verify the durations and crew loading needed to hit it, and price any acceleration, overtime, or phasing the dates imply. Flag aggressive milestones as risk items so the bid carries appropriate contingency or a qualification rather than absorbing hidden schedule pressure.

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