An As-Built But-For Schedule Delay Analysis1 (ABBF) is a retrospective CPM schedule delay analysis technique that determines the earliest date that the required mechanical completion activity, project completion activity, or various milestone activities could have been achieved but-for the owner-caused compensable delays that occurred during the project.2 The amount of ownercaused delay determined from the ABBF Schedule Delay Analysis quantifies the contractor’s entitlement to receive compensable delay damages. Similarly, the analysis could determine the earliest date that the various completion activities could have been achieved but-for the contractorcaused noncompensable delays that occurred during the project.
While the ABBF Schedule Delay Analysis can be calculated using the entire period of the project as one as-built schedule,3 the ABBF Schedule Delay Analysis can also be performed in windows or periods of time, where the as-built schedule and its then current critical path can be analyzed separately for each window or period, and cumulatively for the project.4
The ABBF Schedule Delay Analysis is calculated using the actual start and finish dates and actual work sequences of activities in the as-built schedule to determine if delay to the as-built critical path5 during the analysis period has occurred. The as-built critical path during each schedule window may be different from the planned critical path at the start of each schedule window, due to delays, scope changes, etc., that have occurred during the schedule window. Therefore, the ABBF Schedule Delay Analysis focuses on responsibility for delays that affected the dynamic nature of the as-built critical path of the schedule window rather than delays that affected the planned critical path at the beginning of the schedule window.
In contrast, the Time Impact Analysis (TIA) or the Update Impact Analysis (UIA) adds impacts to the planned schedule to measure any potential delay. The TIA is calculated on schedules which are statused up through the day before each impact first occurred. The UIA is calculated on schedules which are statused at the beginning of a specific window or impact period, typically the monthly schedule updates prepared during the project. Often, a schedule analyst performs a TIA or UIA for the calculation of an extension of time. However, the analyst may incorrectly conclude that the total time extension entitlement or total actual delay is compensable. This conclusion may be incorrect if the analyst fails to address concurrent delays in the as-built schedule, or if the time extension is longer than the actual delay that occurred as the result of acceleration or other delay mitigation.6 The ABBF Schedule Delay Analysis addresses concurrent delays, and the net period of owner-caused delay may be compensable after concurrency of contractor-caused and other excusable delays are addressed.7 Therefore, to avoid an incorrect conclusion, a TIA or UIA can be used to calculate the time extension to which the contractor is entitled as a result of owner-caused and other excusable delays, and the ABBF Schedule Delay Analysis can also be used to determine the compensable delay days to which the contractor is entitled as a result of owner-caused delays.
The ABBF Schedule Delay Analysis is typically more difficult to perform than the TIA or UIA because most CPM software programs regard as-built dates as historical events fixed in time. As a result, most CPM software programs will not permit but-for analysis models to be run on schedules containing actual dates. Consequently, the as-built schedule must be converted to an as-planned format containing “planned” dates that correspond to the as-built schedule but are driven by logic and activity durations. This conversion step is used to create an As-Built Calculation Schedule that can collapse as delays are removed.8
The ABBF Schedule Delay Analysis is performed by first removing owner-caused delays from the As-Built Calculation Schedule and recalculating the project completion date. Contractor-caused (noncompensable) and excusable/noncompensable delays are left in the As-Built Calculation Schedule. The As-Built Calculation Schedule with owner-caused delays removed is used to determine the compensable time period between the actual project completion date and the as-built but-for completion date.
Next, contractor-caused delays are removed from the original As-Built Calculation Schedule and the project completion date is recalculated. Owner-caused (compensable) and excusable/noncompensable delays are left in the As-Built Calculation Schedule. The ABBF Schedule Delay Analysis that removes contractor-caused delays is used to determine the time period between the actual completion date and the as-built but-for completion date for assessment of liquidated damages by the owner.9
The conclusions derived from the ABBF Schedule Delay Analysis are described in more detail in Section 5 of this article.
The following information is provided in this article:
- Why the application of the ABBF Schedule Delay Analysis methodology is appropriate;
- The As-Built Calculation Schedule;
- Quantification of delays;
- Interpreting the results of removing delays from the As-Built Calculation Schedule; and
- Overcoming criticisms of the ABBF Schedule Delay Analysis Method.
2. WHY THE APPLICATION OF THE ABBF SCHEDULE DELAY ANALYSIS METHOD IS APPROPRIATE
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