Window Analysis (Time Impact Analysis – TIA) in Construction.

Introduction

The Window Analysis, also known as Time Impact Analysis (TIA), is a commonly used technique for analyzing delays and disruptions in construction projects. This method is primarily used for prospective delay analysis, which helps forecast the impact of potential delays on the overall project completion. It can also be used retrospectively to evaluate the impact of delays that have already occurred. The TIA breaks the project into smaller periods, called “windows,” and analyzes the effect of delays within each window on the project’s critical path and overall schedule.

The primary objective of Window Analysis is to assess the cumulative impact of delays and to determine whether an Extension of Time (EOT) is justified. By doing so, it helps to allocate responsibility for delays between the contractor, the client, and external factors.

Key Components of Window Analysis (TIA)

1. Baseline Schedule:

• The baseline schedule is the project’s original plan, which includes the sequence of activities, their durations, and the overall project completion date. It serves as the point of reference for assessing delays.

1. Window Periods:

• The project timeline is divided into smaller intervals or “windows,” usually defined by monthly or quarterly periods. Each window is analyzed separately to identify any delays or disruptions that occurred during that period.

1. Delay Events:

• The delay events that occur in each window are identified and their impact on the project schedule is evaluated. These delays could include design changes, weather conditions, or resource shortages.

1. Critical Path Analysis:

• The critical path is recalculated after each window to assess how delays affect the overall project schedule. Changes in the critical path due to delays are noted.

1. Impact on Completion Date:

• After analyzing all windows, the cumulative effect of the delays is determined. This shows how much the project’s completion date is extended due to the delays.

Steps in Window Analysis (Time Impact Analysis)

1. Prepare the Baseline Schedule:

The first step is to develop a baseline schedule. This schedule includes all project activities, their durations, dependencies, and the planned completion date. The baseline schedule serves as the starting point for comparing actual progress against planned progress.

2. Divide the Project into Windows:

The project schedule is divided into smaller time periods or windows (e.g., monthly or quarterly periods). These windows are selected based on project milestones, key phases, or calendar periods. The purpose of dividing the schedule is to assess delays on a more granular level, allowing for detailed analysis of each period.

3. Identify Delay Events in Each Window:

During each window, any delay events that occurred are identified. These could include:

• Excusable Delays: Delays outside the contractor’s control (e.g., adverse weather conditions, client-caused delays).
• Non-Excusable Delays: Delays caused by the contractor (e.g., poor planning, resource shortages).
• Compensable Delays: Delays caused by the client, for which the contractor may seek compensation.
• Concurrent Delays: Overlapping delays that are caused by both parties or multiple factors.

4. Update the Schedule after Each Window:

At the end of each window, the schedule is updated to reflect the actual progress and the impact of the delay events within that window. The critical path is recalculated to see if any delays affected the critical activities, and the schedule is adjusted accordingly.

5. Evaluate the Impact of Delays:

For each window, the delay events are assessed to determine their impact on the critical path and the project’s completion date. If a delay affects critical path activities, it will likely extend the project’s completion date.

6. Cumulative Delay Impact:

After evaluating all windows, the cumulative impact of the delays on the overall project schedule is determined. This provides a comprehensive view of how delays over the course of the project impacted the final completion date.

7. Prepare Extension of Time (EOT) Claim:

Based on the analysis, the contractor prepares an Extension of Time (EOT) claim if the delays are excusable and affect the critical path. The EOT claim includes the new project completion date and supporting evidence of the delay events.

Example of Window Analysis (TIA)

Scenario:

A contractor is building an office complex, and the project is divided into three phases: Foundation Work, Structural Work, and Finishing Work. The project has a baseline completion date of December 31. During the project, delays occurred due to design changes, bad weather, and resource shortages. The contractor uses a monthly window analysis to evaluate the impact of these delays.

Step 1: Baseline Schedule

• The baseline schedule shows that the project was planned to be completed by December 31, with critical path activities spanning all three phases.

Step 2: Divide into Windows

• The project is divided into monthly windows (January to December).

Step 3: Identify Delay Events in Each Window

• January Window: A client-requested design change causes a 15-day delay in foundation work.
• March Window: Bad weather causes a 10-day delay in structural work.
• June Window: The contractor faces a shortage of materials, causing a 20-day delay in finishing work.

Step 4: Update the Schedule after Each Window

• At the end of January, the delay from the design change is incorporated into the schedule, and the critical path is recalculated. The delay pushes the project completion date to January 15.
• At the end of March, the delay from bad weather is added, pushing the completion date to January 25.
• At the end of June, the delay due to the material shortage is added, pushing the completion date to February 15.

Step 5: Evaluate the Impact of Delays

• January Delay (Client’s Design Change): This delay is excusable and compensable since it was caused by the client. It affected the critical path, so the completion date is extended by 15 days.
• March Delay (Bad Weather): This delay is excusable but not compensable. It affected the critical path and extended the project by 10 days.
• June Delay (Contractor’s Material Shortage): This delay is non-excusable because it was caused by the contractor. It also affected the critical path, extending the project by 20 days.

Step 6: Cumulative Delay Impact

• The overall impact of the delays is a 45-day extension of the project completion date (15 days from the client’s design change, 10 days from bad weather, and 20 days from the contractor’s material shortage).

Step 7: Prepare EOT Claim

• The contractor can claim an Extension of Time for 25 days (15 days for the client’s design change and 10 days for bad weather). The contractor is responsible for the 20-day delay caused by the material shortage and cannot claim an EOT for this portion.

Advantages of Window Analysis (TIA)

1. Dynamic and Ongoing Analysis: Since the project is divided into windows, the schedule is continuously updated. This allows for real-time delay assessment and proactive decision-making.
2. Granular Detail: By breaking the project into smaller windows, the analysis provides a detailed view of how each delay event impacted the project schedule.
3. Effective for Large Projects: This method is especially useful for complex and long-duration projects, where delays can occur at various stages of the construction process.
4. Accurate for Dispute Resolution: It provides clear evidence of delay events, making it suitable for dispute resolution and arbitration cases where delay responsibility needs to be established.

Disadvantages of Window Analysis (TIA)

1. Resource-Intensive: TIA requires a significant amount of time and resources to prepare, as it involves regular updates and recalculations of the schedule after each window.
2. Requires Detailed Documentation: Accurate records of delay events, weather conditions, and resource availability are necessary for the analysis to be effective.
3. Potential for Complexity: For highly complex projects with multiple delays, the window analysis can become cumbersome, especially when dealing with concurrent delays or overlapping windows.
4. Difficult to Implement Retroactively: While it can be used for retrospective analysis, TIA is most effective when conducted in real-time. Retroactive application may miss some of the dynamic interactions between activities and delays.

Concurrent Delays in Window Analysis

Concurrent delays occur when two or more delay events take place at the same time but are caused by different parties. In a window analysis, concurrent delays are carefully examined to determine whether both delays affected the critical path and which party is responsible. If one delay is excusable (e.g., client-caused) and the other is non-excusable (e.g., contractor-caused), the analysis must determine whether the contractor is entitled to an EOT or compensation.

Conclusion

The Window Analysis (Time Impact Analysis – TIA) is a robust and flexible delay analysis technique that provides a detailed, periodic assessment of delay events during the course of a construction project. By dividing the project into windows, it allows for continuous monitoring of the project’s critical path and provides a dynamic tool for determining the impact of delays on the overall project schedule. TIA is especially useful in complex