The Most Common Primavera P6 Schedule Errors That Get Flagged in Owner Review

After reviewing contractor-submitted Primavera P6 schedules on behalf of public agencies and owners across dozens of projects, the same errors appear repeatedly. Most of them are not the result of inexperience with P6 — they are the result of building schedules quickly without checking them against the standards that experienced reviewers apply.

Here is what to check before your next baseline or monthly update submission.

Open-Ended Activities

Every activity in the schedule — with the exception of the project start milestone — should have at least one predecessor relationship. Every activity — with the exception of the project completion milestone — should have at least one successor. Open-ended activities create false float, distort the critical path, and are immediately flagged by any reviewer using the standard P6 schedule check report.

Run a schedule check before every submission. P6 identifies open-ended activities directly. There should be zero.

Excessive Lags on Relationships

Lags inserted on finish-to-start relationships are often used as a substitute for missing activities or to represent durations that should be modeled as separate work items. Reviewers flag lags over five to ten days as potential logic manipulation. If a lag represents real work — a concrete cure period, a permit review window, a material lead time — model it as an activity. If it does not represent real work, remove it.

Hard Constraints on Non-Milestone Activities

Must-Start-On, Must-Finish-On, and Finish-No-Later-Than constraints imposed on regular construction activities artificially restrict float and distort the critical path. Constraints should be used only where the contract requires them — typically on interim milestones and the project completion date. Every hard constraint on a non-milestone activity requires justification.

Resource Loading That Does Not Match the Contract Value

When a schedule is cost- and resource-loaded, the total budgeted cost should reconcile to the contract value. Schedules where the loaded cost is significantly below the contract value — a common occurrence when only selected activities are loaded — signal that the resource loading is nominal rather than real. Reviewers on USACE and Port Authority projects check this directly.

Out-of-Sequence Progress

In monthly updates, out-of-sequence progress — where an activity is reported as progressing before its predecessor is complete — should be identified and the schedule logic corrected to reflect actual execution. Retained logic versus progress override settings in P6 affect how out-of-sequence progress is calculated. Most agency specifications require retained logic. Check your project settings before every update.

Activity Descriptions That Do Not Identify Location

Activity names like Structural Steel Erection or MEP Rough-In are not useful in a schedule with hundreds of activities performing similar work in different areas. Activity descriptions should identify the location, level, zone, or building that the work is occurring in. This is essential both for schedule clarity and for delay analysis, where the location context of each activity is critical.