Preconstruction — Scheduling & Phasing

Baseline Schedule

The approved, frozen version of the schedule that progress is measured against for the life of the job.

Quick Answer

A baseline schedule is the approved, frozen version of the project schedule agreed at the start, kept as a fixed reference. As work proceeds, actual progress is compared against the baseline to measure variance, delays, and acceleration. It is the as-planned yardstick that makes delay analysis and progress reporting possible throughout the project.

The Full Picture

A baseline schedule exists because you can't measure progress or delay without a fixed reference to compare against. If the plan simply changes every time reality does, there's no way to say a project is behind or to prove what caused a slip. The baseline freezes an agreed as-planned version so change can be measured against it.

Mechanically, once the initial CPM schedule is reviewed and accepted by the owner and contractor, it's saved as the baseline. The working schedule is then updated with actual start dates, actual durations, and progress. Comparing the current schedule to the baseline yields schedule variance: which activities are ahead, which are behind, and by how much.

In practice, the baseline is central to delay claims and dispute resolution. As-planned versus as-built comparisons rest on the baseline being a fair, achievable starting point. A baseline that was unrealistic or poorly built undermines every progress report and claim that references it, which is why owners often require the baseline to be reviewed and approved before work starts.

For preconstruction, the baseline is typically established as the project transitions into construction, capturing the agreed plan that precon produced. Baselines can be formally revised (re-baselined) when scope changes significantly, but casual changes defeat the purpose. The discipline is changing the baseline only through a controlled process, not whenever the current schedule slips.

Real Examples

→Variance reporting: A monthly update shows structural steel is 12 days behind the baseline, quantifying the slip instead of relying on a vague sense that the job is late.
→Delay claim basis: A contractor's time-extension request compares the as-built dates against the approved baseline to demonstrate the impact of an owner-directed change.
→Controlled re-baseline: After a major scope addition, the team formally re-baselines with owner approval so future progress is measured against a plan that reflects the new scope.

Common Misconceptions

People assume: The baseline schedule gets updated as the project progresses.

Actually: The baseline stays frozen; it's the working schedule that gets updated with actuals. Progress is measured by comparing the updated working schedule to the fixed baseline. Changing the baseline casually destroys its value as a reference.

People assume: Any schedule can serve as a baseline.

Actually: A useful baseline has to be reviewed and approved as realistic and achievable before work starts. An unvetted or padded baseline makes every variance report and delay claim built on it unreliable.

Does MeltPlan Solve This?

Not directly

Not directly. Setting a baseline and tracking variance against it are CPM scheduling functions outside MeltPlan's scope. MeltPlan focuses on preconstruction document and estimating work such as drawing review, takeoff, and bid leveling. To establish and manage a baseline schedule you'll want a dedicated CPM tool like Primavera P6 or Microsoft Project.

Frequently Asked Questions

What is the purpose of a baseline schedule?

To provide a fixed, approved reference so actual progress can be measured against the original plan. Without a baseline there's no objective way to determine whether a project is ahead or behind or to support a delay claim.

Can a baseline schedule be changed?

Yes, but only through a controlled re-baselining process, usually with owner approval, typically after a significant scope change. Casually changing the baseline whenever the schedule slips defeats its purpose as a stable reference.

What is the difference between a baseline and the current schedule?

The baseline is the frozen as-planned version. The current (working) schedule is updated with actual progress. The comparison between them produces schedule variance and drives progress reporting.

When is the baseline schedule set?

Usually at the start of construction, once the initial CPM schedule is reviewed and approved by the owner and contractor. It captures the agreed plan that preconstruction produced.

Related Terms

CPM ScheduleA logic-linked schedule that calculates which chain of activities controls the finish date.Critical PathThe chain of dependent activities whose total length determines the project finish date.Float (Schedule)The slack an activity has before its delay starts to push other work or the finish date.Master ScheduleThe top-level, whole-project timeline of major phases and milestones from design to closeout.Look-Ahead ScheduleA short-window, detailed plan of the next few weeks of field work, pulled from the master schedule.Preconstruction ScheduleThe timeline for all the design, bidding, and procurement work that has to finish before construction can start.

More Preconstruction — Scheduling & Phasing Terms

Sources

  1. Project Management Institute (PMI) — Practice Standard for Scheduling
  2. AACE International — Planning & Scheduling Recommended Practices
MELTPLAN