In project scheduling, accuracy and reliability are critical. However, a common issue that often goes undetected is out-of-sequence (OOS) progress—when actual work does not follow the planned sequence of activities.

This can significantly distort scheduling forecasts, misrepresent project progress, and introduce delays that impact overall project success.

What is Out-of-Sequence Progress?

Out-of-sequence progress occurs when an activity starts or finishes before its predecessor is completed, violating the intended logic of the schedule. This deviation can have significant consequences, including:

• Misleading schedule forecasts – The critical path may be distorted, making it difficult to predict project completion accurately.
• Incorrect float calculations – Free and total float values become unreliable, affecting decision-making.
• Resource allocation challenges – Planned dependencies may no longer reflect the actual order of work, leading to inefficiencies.
• Compromised as-built records – Historical data may not accurately reflect how work was executed, reducing its value for future projects.

Why is This Problem So Important?

Schedules are used for more than just tracking progress; they are crucial for forecasting, resource management, contractual claims, and forensic analysis. When out-of-sequence progress is ignored, it introduces uncertainty into all these areas. A project team relying on inaccurate data can make costly mistakes, such as:

• Misallocating resources due to unreliable activity relationships.
• Overlooking the real drivers of project delays.
• Creating misleading As-Built schedules, which can cause disputes in claims analysis.

One of the biggest challenges with out-of-sequence progress is that many scheduling tools fail to properly track historical logic violations. These tools focus primarily on future-looking schedules, rather than analysing whether past execution followed the intended plan.

The Limitations of Primavera P6

While Primavera P6 is widely used for schedule management, it does not have a dedicated feature to check for historic out-of-sequence logic violations. P6 does provide warnings for out-of-sequence activities, but these warnings are limited and do not provide a structured report for users to analyse and correct these violations efficiently.

This gap in P6 means that many projects unknowingly carry logic errors in their schedules, reducing the accuracy of both current progress assessments and retrospective project evaluations.

Tracking and Addressing OOS Progress

To maintain schedule accuracy and reliability, project teams should:

• Identify out-of-sequence progress regularly.
• Analyse why these deviations occur—whether due to changes in execution, incorrect logic, or unforeseen delays.
• Adjust schedule dependencies or update execution plans to align with real-world conditions.
• Ensure As-Built records reflect actual execution for accurate future planning and claims support.

By systematically tracking out-of-sequence progress, teams can improve their schedule integrity, ensure realistic forecasts, and minimise costly errors.

The Role of Historic Logic in Schedule Integrity

Historic schedule logic is essential for accurate As-Built analysis. If scheduling software does not verify whether planned relationships were maintained, historical project data becomes unreliable. This affects:

• Forensic schedule analysis – Inaccurate historical data makes it difficult to determine the root causes of delays.
• Lessons learned for future projects – Incorrect As-Built data reduces the reliability of reference schedules.
• Contractual discrepancies– A lack of verified historical logic can weaken claims and project narratives.
• Ensuring Schedule Integrity for Better Project Outcomes

By recognising the impact of out-of-sequence progress and actively addressing it, project teams can:

• Maintain accurate and actionable schedules.
• Reduce schedule-driven risks and inefficiencies.
• Improve the quality of As-Built records for future analysis.
• Ensure contractual clarity and accurate claims analysis.

Understanding and managing out-of-sequence progress is essential for reliable project scheduling. By implementing structured methods to track and correct logic violations, project teams can ensure that their schedules remain a true reflection of actual work performed.

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