Learning Center
Time Impact Analysis, Step by Step
Time Impact Analysis (TIA) is the forensic-scheduling method for measuring exactly what a single delay event does to a project’s finish date -- by inserting a fragnet into the schedule and recalculating the network. Here’s the full method, worked through on a fictional 13-activity build-out from baseline to time extension.
What TIA Is, and When It’s Used
TIA is a prospective method -- it doesn’t wait until a project is finished to reconstruct what happened. Instead, it takes the accepted schedule update from immediately before a specific delay event occurred, builds a small sub-network called a fragnet (fragmentary network) that models the delay event’s own logic and duration, splices that fragnet into the schedule at the exact point the delay actually intercepted the work, and recalculates the entire network forward. Whatever shift appears at the project’s critical path and completion milestone is the delay event’s measured time impact -- nothing else changes between the two runs.
It’s the method both AACE International (Recommended Practice 52R-06) and the SCL Delay and Disruption Protocol document as the preferred approach for evaluating a time-extension request while the project is still underway, precisely because it isolates one event’s effect without needing to wait for -- or rely on -- how the rest of the project actually played out afterward.
The Baseline Schedule
Thirteen activities for a fictional interior office build-out, data date Day 0. Rough-in work runs in three parallel trades after demolition; HVAC is the longest of the three and, along with the finish-out sequence behind it, drives the 51-workday baseline finish (highlighted rows below).
| Code | Activity | Duration | Predecessor(s) | Baseline Span |
|---|---|---|---|---|
| A | Permits & Mobilization | 5 d | — | Day 0–5 |
| B | Demolition | 5 d | A | Day 5–10 |
| C | Plumbing Rough-In | 8 d | B | Day 10–18 |
| D | Electrical Rough-In | 9 d | B | Day 10–19 |
| E | HVAC Rough-In | 10 d | B | Day 10–20 |
| F | Wall Framing & Insulation | 6 d | C, D, E | Day 20–26 |
| G | Drywall, Tape & Finish | 7 d | F | Day 26–33 |
| H | Interior Doors & Millwork | 6 d | G | Day 33–39 |
| I | Flooring | 5 d | G | Day 33–38 |
| J | Painting | 5 d | H, I | Day 39–44 |
| K | Final MEP Trim & Fixtures | 4 d | J | Day 44–48 |
| L | Punch List & Owner Walkthrough | 3 d | K | Day 48–51 |
| M | Substantial Completion | — | L | Day 51–51 |
Highlighted rows (A, B, E, F, G, H, J, K, L, M) form the baseline critical path -- zero float, finishing Day 51. C (2 days of float), D (1 day), and I (1 day) are near-critical but not driving.
The Delay Event and the Fragnet
On Day 26 -- the moment Wall Framing & Insulation (F) actually finished, and the schedule update immediately before anything went wrong -- the owner issues a directive relocating the electrical panel room to accommodate a last-minute change to the tenant’s server-rack layout. Drywall (G) can’t proceed until revised drawings are approved and the affected framing is reworked. That’s an owner-caused delay event, and it needs a fragnet: three new activities, logically tied in exactly where the delay actually intercepted the work, between F and G.
| Code | Fragnet Activity | Duration | Span |
|---|---|---|---|
| N | Owner Review & Approval — Revised Panel Room RFI | 10 d | Day 26–36 |
| O | Revise Electrical & Framing Drawings | 3 d | Day 36–39 |
| P | Field Rework — Reframe Panel Room Wall | 4 d | Day 39–43 |
The Recalculated Network and the Time Extension
Activities A through F are untouched -- the delay happens after F finishes, so nothing before Day 26 changes. Running the forward pass again with N, O, and P inserted shifts every downstream activity by exactly 17 days, because the fragnet lands on what was already the zero-float critical path and no other path (C at 2 days of float, D at 1, I at 1) comes close to absorbing 17 days of it:
| Code | Activity | Baseline Span | Recalculated Span |
|---|---|---|---|
| G | Drywall, Tape & Finish | Day 26–33 | Day 43–50 |
| H | Interior Doors & Millwork | Day 33–39 | Day 50–56 |
| I | Flooring | Day 33–38 | Day 50–55 |
| J | Painting | Day 39–44 | Day 56–61 |
| K | Final MEP Trim & Fixtures | Day 44–48 | Day 61–65 |
| L | Punch List & Owner Walkthrough | Day 48–51 | Day 65–68 |
| M | Substantial Completion | Day 51–51 | Day 68–68 |
Time extension = Recalculated finish − Baseline finish = Day 68 − Day 51 = 17 workdays. Because the fragnet fell on the update’s existing critical path and every parallel path had less float than the fragnet’s 17-day duration, the full fragnet duration flows through unabsorbed. That won’t always be true -- a fragnet landing on a path with more float than its own duration would show a smaller extension, or none at all.
Doing this on paper for a 13-activity example is manageable. On a real, multi-thousand-activity schedule with dozens of updates, it isn’t. Claims Digger’s schedule comparison shows exactly which activities shifted onto or off the critical path between any two updates, with the specific date and duration changes driving that shift laid out side by side. See how it works.
Frequently Asked Questions
- How is Time Impact Analysis different from a retrospective, as-built delay analysis?
- TIA is prospective. It takes the schedule update from immediately before the delay event, inserts a fragnet to model the event, and recalculates forward to see what the network itself predicts about completion -- rather than reconstructing the critical path after the fact from as-built dates once the project (or the disputed period) is already over.
- Does the TIA have to be prepared at the moment the delay happens?
- Ideally yes, or as close to it as practical -- that contemporaneity is a big part of what makes the projected impact credible. Many contract forms (including common federal and design-professional contract templates) set specific windows for submitting a time-extension request built on a TIA, though analysts sometimes have to reconstruct one later using the update that would have been current at the time.
- What if the fragnet doesn't land on an activity that's already critical?
- Then the network recalculation may show a smaller time extension than the fragnet's own duration, or none at all, if there was enough float on that path to absorb it. A time extension exactly equal to the fragnet's duration -- like in the worked example above -- only happens when the delay lands on a path with little or no float to spare.
- Who has to agree on a TIA before it's binding?
- A TIA is normally prepared by the contractor's scheduler and submitted to the owner or construction manager for review; it typically isn't a unilateral entitlement until the reviewing party accepts the logic, durations, and fragnet placement, or it's resolved through whatever contract mechanism governs disputed time-extension requests.
Part of the Claims Digger Learning Center. Related reading: Concurrent delay: how to actually test for it · Full glossary