A time impact analysis (TIA) is a forward-looking schedule method that measures how a specific delay or change would move a construction project’s critical path and completion date. The scheduler inserts a modeled delay, often as a fragnet, into an unimpacted CPM schedule, recalculates the network, and reports the change in finish date in calendar or work days.

That number is not a guess. It is the difference between the unimpacted schedule and the impacted schedule. Owners, contracting officers, and boards use it to decide whether a time extension is due. Contractors use it to protect the completion date, support a request for equitable adjustment, and keep liquidated damages from attaching to a delay they did not cause.

This guide explains what a time impact analysis is, when to run one, how to build it, and how ACE Consulting applies the method on commercial and federal work. It also points back to our February 2025 webinar, Navigating Delays: Time Impact Analysis, led by Diana Hagan, Director of Project Controls and Training.

What is a time impact analysis in construction?

A time impact analysis in construction is a modeled, additive Critical Path Method (CPM) technique. You take the accepted or current unimpacted schedule, add activities that represent a delay or change, and measure whether the longest path and contract completion date move.

AACE International’s Recommended Practice 52R-06, Prospective Time Impact Analysis, describes TIA as a near-real-time forecast used while the project is still underway. The goal is a timely, defensible estimate of time impact so the parties can adjust the contract before the delay hardens into a dispute.

Three results matter:

1. Days of impact. The change in projected completion between the unimpacted and impacted schedules.
2. Driving activities. Which tasks now sit on the longest path because of the event.
3. Entitlement story. Why those days are excusable, compensable, or neither, based on the contract and the facts.

TIA does not prove cost by itself. It proves time. Cost follows in a separate estimate, change order, or request for equitable adjustment that uses the TIA as schedule evidence.

When should you perform a time impact analysis?

Perform a time impact analysis as soon as a delay or change has enough definition to model, and before the next schedule update buries the event. Waiting until substantial completion turns a clean prospective analysis into a forensic argument.

Use a TIA when any of the following is true:

• The owner issues a change that may hit the critical path.
• Differing site conditions, hazardous materials, or design conflicts stop work on a driving activity.
• A government delay in reviews, access, or funding idles the longest path.
• Unusually severe weather, a utility relocation, or a third-party interference consumes float on near-critical work.
• The contract or specification requires a time impact analysis with every time-extension request.
• You need to test mitigation options, such as resequencing or added crews, before you commit to a recovery plan.

Do not wait for the delay to “feel big.” A five-day hit on the longest path is a contract issue. A 30-day hit on a path with 40 days of float may be no time impact at all. The schedule, not the emotion, decides.

How does a time impact analysis work?

A time impact analysis works by comparing two versions of the same CPM network: one without the delay event, and one with the delay event inserted. The difference in the calculated finish date is the time impact, provided the unimpacted schedule is valid and the fragnet logic is honest.

ACE’s project controls teams follow a sequence that matches industry practice and the method Diana Hagan walked through in the 2025 webinar.

1. Verify the unimpacted schedule

Start with the last owner-accepted update, or the current progress schedule with a data date immediately before the event. Check logic, calendars, constraints, and open-ended activities. A TIA built on a broken network will produce a broken answer. If the baseline itself is weak, fix the schedule first. A strong baseline schedule is the reference point every later impact has to stand on.

2. Update status to the data date

Progress the schedule to the day before the delay begins. Actual starts, remaining durations, and percent complete must match the daily reports. If you mix later progress into the unimpacted file, you hide the event you are trying to measure.

3. Define the event and the contract theory

Write down what happened, when it started, who caused it, and which clause applies. Excusable delay, compensable delay, and contractor-caused delay are not interchangeable. The model has to match the theory you will argue in the narrative.

4. Build the fragnet

Create a small network that represents only the delay: discovery, stop-work, investigation, direction, and return to work. Durations need a source, such as an RFI, a government letter, a lab report, or a crew log. Do not pad. Do not skip a real restraint.

5. Insert the fragnet into a copy of the schedule

Never overwrite the unimpacted file. Tie the fragnet to the affected activities with the same relationship types the rest of the job uses. Then recalculate CPM.

6. Measure the impact

Compare projected completion, milestone dates, and longest-path activities. The time impact is the movement of the completion date, not the duration of the fragnet. A 20-day event on a path with 12 days of float is an 8-day impact, not a 20-day impact.

7. Write the narrative and attach the records

The schedule files show the math. The narrative shows why the math is entitled. Include the unimpacted and impacted layouts, a fragnet diagram, a delay chronology, and the source documents. Then submit it with the time-extension request, change proposal, or REA package.

What is a fragnet in a time impact analysis?

A fragnet, short for fragmentary network, is a mini-schedule that models one delay or change. It is not the whole job. It is the slice of logic needed to show how that event enters the CPM network and whether it drives the longest path.

In the 2025 webinar, ACE used a hazardous material discovery as the working example. The fragnet captured the stop, the testing, the owner’s direction, and the restart, then dropped that sequence onto the affected activity. That is the right level of detail: enough to be true, not so much that the model becomes a second project schedule.

For a fuller treatment of how fragnets sit inside CPM, see ACE’s guide to the fragnet in construction scheduling.

Prospective TIA vs. retrospective delay analysis

Prospective time impact analysis forecasts impact while the work is still moving. Retrospective analysis looks backward after the delay has run its course. Both use CPM. They answer different questions and rest on different records.

Question	Prospective TIA (RP 52R-06)	Retrospective / forensic analysis (RP 29R-03)
When it is performed	During the project, near the event	After the delay, often in a claim or dispute
Primary question	What will this event do to completion?	What did this event actually do to completion?
Schedule used	Unimpacted current or accepted update	As-built, windows, or collapsed as-built methods
Strength	Timely, contract-friendly, easier to negotiate	Can incorporate actual progress and concurrency after the fact
Risk if misused	Overstates impact if the schedule is wrong or the fragnet is padded	Looks like hindsight advocacy if contemporaneous TIAs were never done

AACE’s Recommended Practice 29R-03, Forensic Schedule Analysis, covers the retrospective methods. It is a taxonomy, not a mandate to pick one technique for every dispute. If you ran clean TIAs during the job, the forensic fight later is smaller. That is the point of doing the work in real time.

Time impact analysis vs. other delay methods

Time impact analysis is one delay method, not the only one. Contracts and specifications sometimes name TIA. Sometimes they ask for a “schedule impact analysis” without defining the technique. Match the method to the contract, the available records, and the timing of the event.

Method	What it compares	Best use
Time impact analysis	Unimpacted CPM vs. CPM plus a modeled event	Contemporaneous time-extension requests
Impacted as-planned	Baseline plus delays, with little or no progress status	Early events, when updates are thin (use with caution)
Windows / contemporaneous period analysis	Critical path in successive update periods	Multiple delays over a long job
Collapsed as-built	As-built network with delay activities removed	After-the-fact studies when daily records are strong
As-planned vs. as-built	Original plan against what actually occurred	High-level variance, not a substitute for CPM entitlement

If the specification requires TIA, do not substitute a bar-chart variance and call it analysis. Reviewers see that immediately.

What documentation does a TIA need?

A time impact analysis needs contemporaneous records that prove three things: the event happened, it affected driving work, and the durations in the fragnet are real. Software output without source documents is a chart, not a claim.

Build the file around:

• The unimpacted schedule (XER or MPP, PDF layouts, and the narrative from that update)
• The impacted schedule and a clear fragnet diagram
• Daily reports, delay notices, RFIs, submittal logs, and owner or contracting officer correspondence
• Photos, test results, access logs, or stop-work orders tied to dates
• A chronology that starts at the first notice of the event
• Contract clauses, including notice requirements and float language

Notice is not optional. Many federal clauses require written notice within a short window. A perfect TIA filed after the notice period can still fail. Pair the analysis with the notice, then keep updating the file as facts change.

How federal contracts treat time impact analysis

Federal construction contracts rarely use the phrase “time impact analysis” in the FAR itself. They still expect a CPM-based showing that a delay was beyond the contractor’s control and that it affected completion. FAR 52.249-10, Default (Fixed-Price Construction), is the clause most teams meet first. It lists excusable causes, including acts of the government, unusually severe weather, and certain subcontractor delays, and it requires prompt written notice. Time may be extended. Money is a separate question under the Changes clause, differing site conditions, or a suspension of work.

Agency specifications go further. U.S. Army Corps of Engineers and NAVFAC schedule sections often require a schedule impact analysis with any time-extension request, tied to the approved project schedule and the longest path. Government-caused delay that does not move the critical path does not earn time. Contractor delay that sits on the longest path does not earn time either.

That is why ACE treats TIA as part of project controls, not as a last-minute claims product. Monthly updates, clean logic, and a current critical path are what make a later TIA believable. When the delay is real and the days are due, the same file supports the time request and, if costs follow, the REA. If the path can still be recovered, the next product is a recovery schedule, not a padded fragnet.

Common time impact analysis mistakes

Most failed TIAs fail for the same reasons. The method is not mysterious. The inputs are sloppy.

• Using a stale or unaccepted schedule. If the owner never accepted the update, say so and explain why it is still the right unimpacted file.
• Inserting the fragnet into the wrong data date. Status after the event hides the impact.
• Equating fragnet duration with project delay. Float on the affected path has to be consumed first.
• Ignoring concurrent delay. A contractor manpower problem on the same path as an owner design delay changes entitlement.
• Hard constraints that freeze the finish date. Must-finish-on dates can mask true longest-path movement.
• No narrative. Reviewers will not reverse-engineer your P6 file.
• Waiting until the claim phase. Prospective TIA is faster to defend and more credible than a forensic rebuild.

If you cannot defend a duration with a document, do not put it in the fragnet. Integrity in the model is the whole product.

Lessons from ACE’s Navigating Delays webinar

In February 2025, ACE Consulting hosted Navigating Delays: Time Impact Analysis. Diana Hagan, Director of Project Controls and Training, taught the method. Josh Jewell moderated. The session is available as a replay on ACE’s webinar page and in the webinar replay library.

The teaching points still hold:

• Separate excusable delay from inexcusable delay before you model. Weather and owner procurement problems are not the same as manpower shortages or deficient work.
• The schedule has to be true before the TIA starts. Correct logic, correct sequencing, and monthly updates are not paperwork. They are the instrument.
• Preparation is a sequence, not a single P6 click. Verify the schedule, update it, define the scope of the delay, build the fragnet, then write the narrative.
• Documentation carries the claim. The webinar stressed contemporaneous records as the difference between a negotiation and a fight.
• TIA is a management tool, not only a claims tool. A clear impact number helps the team decide whether to resequence, add resources, or request time.

The Q&A covered government responsiveness, float ownership, and weather delays. Those three topics still generate most of the confusion on federal jobs. Float belongs to the project unless the contract says otherwise. Weather is only a time event when it is unusually severe and it hits driving work. Government lag is only a delay when you can show the review or access sat on the longest path.

Frequently asked questions

Get the delay on paper before it becomes a dispute

A time impact analysis is how construction teams turn a delay story into a measured effect on the critical path. Done during the job, with a current schedule and a tight fragnet, it gives the owner a number they can act on and gives the contractor a file that will still make sense a year later.

If you are staring at a change, a stop-work, or a review lag and you are not sure whether completion moved, that is the moment to run the TIA. ACE Consulting builds and reviews time impact analyses as part of our project controls practice, the same discipline we taught in the Navigating Delays webinar.

Watch the Navigating Delays: Time Impact Analysis replay, or contact ACE at ace-consulting.net/project-controls to put a competent scheduler on the impact before the update cycle erases it.