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Published June 2021, Updated April 2023

Which Schedule to Use in a Time Impact Analysis TIA

Which Schedule to Use in a Time Impact Analysis (TIA)

Published November 2022


Source (with permission): AACEI RP 52R-06, page 2/8

Which Schedule to Time Impact Analysis TIA Prior to Delay
Source (with permission): AACEI RP 52R-06, page 5/8

This section also refers to an AACE (currently AACEI) recommended practice (RP) 52R-06. If you’re unfamiliar with AACEI, it’s the Association for the Advancement of Cost Engineering, and they compile industry best practices for project controls.


RP 52R-06 states “the appropriate schedule should be the last Owner-accepted schedule statused and updated prior to the time of the change or delay”.

Which Schedule to Use in a Time Impact Analysis TIA

RP 52R-06 also clarifies the schedule as “an accepted CPM schedule, with a status date immediately just prior to the delaying event”, and that it “must be developed that has no reference to the delay in question.”

Which Schedule to Use in Time Impact Analysis TIA
Time Impact Analysis TIA Federal Military Construction Schedule

In this article, we talked about which schedule to base a Time Impact Analysis (TIA) on. This schedule serves as the “unimpacted” schedule that’s compared to the TIA “impacted” schedule, and also as the schedule the TIA activities are added into to model the impact.


It’s important to use the correct schedule because it sets a fair and objective starting point for the analysis. Using the wrong schedule could give you inaccurate or skewed results.


In a Time Impact Analysis, use the schedule *most recent to but prior to* the date of impact as a basis for analysis.


Hope this was helpful.


Questions or comments? Reach us at connect@cpm-ss.com.


Thanks for reading.


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Summary

For a Time Impact Analysis, first determine the date of impact. This is when the issue first arose, preventing the working from moving forwards had it not occurred.


Next, find the schedule most recent but prior to that date of impact.


Putting it All Together

Source: UFGS 01 32 01.00 10, updated Feb-2015

Let’s look at the requirements in the standard UFGS 01 32 01.00 10 scheduling specification.


The snapshot below states “the last approved schedule prior to the first day of the impact or delay” is to be used as the basis for a Time Impact Analysis.

Federal and MILCON Time Impact Analysis (TIA) Requirements

Before we get into which schedule to use, let’s first define the TIA’s “date of impact”.


The date of impact is the start of any delaying event, change in conditions, or unexpected circumstances that prevent the work from moving forwards.


Examples can include:


  • When an unknown site condition was discovered
  • Direction from the owner to stop work
  • Notification or awareness or an issue


In other words, the date of impact is when the issue first arose, preventing the work from moving forwards had it not occurred.

Date of Impact

In this article, we’re going to talk about which schedule to use in a Time Impact Analysis (TIA) – a critical step to get right early on in the process for a fair and accurate analysis.


This schedule serves two purposes:


  1. As the “unimpacted” schedule compared to the TIA “impacted” schedule, and
  2. After a copy is made, the schedule the TIA activities are added into to model the impact.


Selecting the correct schedule sets a fair and objective starting point for the analysis. Using the wrong schedule as the basis for analysis could result in inaccurate or skewed results.


In this article, we’ll help clarify this step and explain the why behind the requirements and guidance we refer to for federal and military construction (MILCON) projects.


In a Time Impact Analysis, use the schedule *most recent to but prior to* the date of impact as a basis for analysis.


In the sections below, we’ll cover:


  • Date of Impact
  • Federal and Military Construction Time Impact Analysis (TIA) Requirements
  • Putting It All Together


Note: This article is provided for informational use only and does not supersede any requirements in your contract. As delays have varying levels of complexity, this article is intended simply to serve as a starting point.

Using the schedule most recent to but prior to the date of impact is important because:


  • This schedule represents what’s known by all parties at the time. If a schedule “after the fact” is used instead, it could have been manipulated to set up the delay to either exaggerate or minimize it, whatever is the desired outcome is.


  • Even if the schedule isn’t perfect, it reflects the team’s understanding of the project and plan at the time. This is also what AACEI literature refers to as the “contemporaneous” schedule.


  • This schedule serves as the “unimpacted” schedule that the TIA “impacted” schedule is compared to. If you use a schedule updated after the date of impact, it could already be reflecting delay, so you wouldn’t have the “unimpacted” schedule to compare it to. You need both.


Selecting the correct schedule to base the analysis provides a fair and objective starting point for the analysis.


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This blog is for general informational purposes only and is not to be considered an official interpretation or enforcement policy of the UFGS standard specifications. As individual project requirements vary, refer to your specific contract. See our Terms and Conditions and Disclaimer for additional information.

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