What is a fragnet in a time impact analysis?

A fragnet is a fragment of network activities that models a specific delay event. Instead of describing the delay in words, the analyst builds the handful of activities that represent it, with their durations, logic ties, and any resource constraints, as a small piece of schedule. That fragment is then inserted into the project's most recent schedule update at the point in time the event occurred. When the Critical Path Method calculation is rerun with the fragnet in place, the schedule itself shows whether the event pushed the completion date and by how much. A well-constructed fragnet is the difference between a defensible TIA and one that is rejected, because it has to reflect what actually happened, not an exaggerated version of it.

Why is TIA called prospective, and when is it used?

It is prospective because it models the impact forward from the moment the event occurred, using the schedule as it stood at that time, rather than reconstructing the whole project after the fact. That makes it the natural method for contemporaneous change-order delay claims: when a delay event happens mid-project, a TIA on the current update shows the time impact that should accompany the change order. Retrospective methods, such as as-planned versus as-built or window analysis, look backward over completed work and are used when a dispute is assessed after the fact. TIA is referenced in AACE International Recommended Practice 52R-06 and is widely accepted when it is built on a contemporaneous, properly updated schedule.

What makes a time impact analysis defensible?

A contemporaneous schedule, a faithful fragnet, and clean critical-path logic. The analysis has to start from a schedule update that reflected the project as it actually stood just before the event, not a stale baseline. The fragnet has to model the real delay honestly, and the Critical Path Method logic has to be sound so the measured impact genuinely flows from the event rather than from a modeling artifact. The event should be isolated so its impact is not tangled with unrelated slippage. And the whole analysis is far stronger when the underlying facts, the dates, the field conditions, the notice, are backed by contemporaneous daily reports rather than recollection. A TIA is only as credible as the schedule and the records it rests on.

Construction Glossary · Change Management

Time ImpactAnalysis

You do not argue a delay's impact. You model it. TIA inserts the delay into the live schedule and lets the critical path say how many days it cost.

Definition

Time Impact Analysis (TIA) is a prospective delay-analysis method that quantifies the schedule impact of a single delay event or change. The analyst builds a fragnet, a small fragment of activities modeling the delay, inserts it into the most recent schedule update, reruns the Critical Path Method calculation, and measures how far the projected completion date moves. It is the method most widely accepted for contemporaneous change-order delay claims.

Insert the fragnet, rerun the path

A differing site condition on our $12.0M project is modeled as a fragnet between activities B and C. Rerunning the Critical Path Method pushes the finish eighteen working days, net of the float the delay consumed.

TIA among the forensic methods

AACE International Recommended Practice 29R-03 recognizes four primary methods. TIA is the one built for the live project, not the post-mortem.

Method	Direction	Best used for
Time Impact Analysis (TIA)	Prospective	A single event during the project, for a change-order claim
As-Planned vs As-Built	Retrospective	The simplest after-the-fact comparison
Window Analysis	Retrospective	The most rigorous: delay attributed period by period
Collapsed As-Built	Retrospective	Working backward from the as-built schedule

The full method comparison lives in the delay-analysis methodologies guide.

How POD feeds a TIA

A TIA is run in the scheduling tool, and POD provides the substrate it needs. POD reads the imported Primavera P6 or MS Project schedule, including activity float and the critical path, and keeps the contemporaneous record a credible fragnet is built from: the dated daily reports, the delay event, and the notice trail. POD does not run the Critical Path Method itself or construct the fragnet for you; the network calculation stays in the scheduling software. What POD removes is the scramble to reassemble what the schedule looked like and what happened in the field on the day the event hit.

Delay analysis methodologies guide

Frequently asked questions

A TIA rides on a change order

The time impact a TIA measures is the extension that should travel with the change order for the delaying event.

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