What Is an As-Built Schedule? (And How to Build One)

Introduction

An as-built schedule is a detailed record of what actually happened on a construction project—when each activity started, finished, and how long it took. Unlike the baseline schedule (the plan) or the target schedule (the updated plan), the as-built schedule captures reality. It is essential for analyzing delays, supporting claims, and closing out projects.

What Is an As-Built Schedule?

An as-built schedule is a time-scaled representation of the actual sequence and duration of all project activities. It shows the actual start and finish dates for each task, often including logic ties that reflect how work was actually performed. It can be presented as a Gantt chart, a tabular report, or a Primavera P6 XER file.

Key characteristics:

• Actual dates: Each activity has an actual start and actual finish.
• Actual durations: The calendar days or workdays between actual start and finish.
• As-built logic: The sequence of work as it occurred (may differ from planned logic).
• Updates: Often built from periodic schedule updates (weekly or monthly).

Why Is an As-Built Schedule Important?

1. Delay Claims and Forensic Analysis

In construction disputes, the as-built schedule is the foundation of most delay analysis methods. Whether you use a contemporaneous period analysis, time impact analysis, or collapsed as-built technique, you need an accurate record of what happened. Without it, you cannot prove entitlement to time extensions or demonstrate the impact of owner-caused delays.

2. Project Closeout and Lessons Learned

Owners often require an as-built schedule as part of closeout documentation. It helps them understand the actual timeline for future maintenance and operations. For contractors, comparing the as-built to the baseline reveals where estimates were off and where productivity can be improved.

3. Legal and Contractual Compliance

Many contracts (e.g., EJCDC, FIDIC) require the contractor to maintain and submit an as-built schedule. Failure to do so can result in withheld payments or weakened claim positions.

How to Reconstruct an As-Built Schedule from Primavera P6 Updates

If you have been maintaining regular schedule updates in Primavera P6, you already have most of the data needed. Here is a step-by-step approach:

Step 1: Gather All Schedule Updates

Collect every XER file (or P6 database backup) from project start to finish. Each update should contain actual dates for completed activities.

Step 2: Extract Actual Dates

For each activity, find the earliest actual start and the latest actual finish across all updates. This gives you the true as-built dates. In P6, you can use the Schedule Log or compare baseline vs. update using a tool like Project Assure (free, browser-based XER analyser) to automatically extract actual dates.

Step 3: Build the As-Built Logic

Original logic often becomes invalid as work progresses. Reconstruct as-built logic by:

• Reviewing daily reports, photos, and meeting minutes.
• Using the actual start/finish dates to infer sequences (e.g., if drywall started after MEP rough-in finished, that is the as-built relationship).
• Adjusting relationships in P6 by setting all activities to actual dates and then using the Schedule command with a data date after project completion to let P6 recalculate logic (though this may not be perfect).

Step 4: Validate the As-Built Schedule

Check for inconsistencies:

• No activity should have an actual finish before its actual start.
• All milestones should have actual dates.
• Total float should be zero or consistent with actual delays.

You can run a DCMA 14-point check on your as-built XER using Project Assure to catch common errors like missing actual dates or negative float.

Common Pitfalls When Building an As-Built Schedule

Pitfall 1: Using Only the Last Update

If you only look at the final schedule update, you may miss activities that were added or removed mid-project. Always use all updates.

Pitfall 2: Ignoring Out-of-Sequence Progress

In P6, when an activity finishes before its predecessor, it creates out-of-sequence progress. Simply copying actual dates from updates may produce a schedule that shows work starting before it could have. You must resolve these by adjusting logic or splitting activities.

Pitfall 3: Assuming Planned Logic is As-Built Logic

Just because the baseline said Task A precedes Task B does not mean it happened that way. Always verify with field records.

Pitfall 4: Not Including All Activities

Some contractors only update key milestones, leaving many activities with no actual dates. For a reliable as-built schedule, every activity that was performed must have dates. Use daily logs to fill gaps.

Pitfall 5: Overlooking Weather and Non-Work Days

If your calendar includes non-work days, ensure that actual dates align. A task that took 5 calendar days might only be 3 workdays if it spanned a weekend.

Using an As-Built Schedule for Delay Claims

Once you have a reliable as-built schedule, you can perform various delay analyses:

• As-Planned vs. As-Built: Compare baseline dates to actual dates to identify delays.
• Collapsed As-Built: Remove excusable delays from the as-built to see the theoretical completion date without those delays.
• Time Impact Analysis: Insert delay events into the as-built and measure the impact.

For a quick comparison of baseline and as-built, you can use Project Assure to upload both XER files and get a side-by-side view of activity variances, float changes, and critical path shifts.

Conclusion

An as-built schedule is not just a historical record; it is a powerful tool for protecting your contractual rights and improving future performance. By methodically reconstructing actual dates and logic from your updates, you can create a reliable as-built that stands up to scrutiny. Avoid common pitfalls by validating your data and using automated checks. With the right approach, your as-built schedule will be your strongest asset in any delay claim or closeout negotiation.