TIA vs Windows Analysis vs Collapsed As-Built: Which Method Actually Holds Up in Court?

Three hours into a deposition, opposing counsel asks the delay expert why they chose a Collapsed As-Built methodology instead of a Time Impact Analysis. The expert's answer will matter more than most of the substantive testimony that follows.

Methodology selection is the hinge on which most schedule delay claims turn. Pick the right method for the case, and the expert defends ground. Pick the wrong one — or, worse, pick one that was convenient given the available data rather than appropriate to the facts — and the deposition shifts from "is there a delay?" to "is this analysis even credible?"

Once the credibility of the methodology is in question, the substantive findings rarely survive.

This article compares the three most commonly used delay analysis methods — Time Impact Analysis (TIA), Windows Analysis, and Collapsed As-Built (also called "but-for" analysis) — on the dimensions that actually matter: evidentiary defensibility, data requirements, cost and complexity, and the specific fact patterns each method handles well.

The goal isn't to declare a winner. It's to help the people who choose — attorneys building a claim, claim consultants scoping an engagement, or project teams evaluating an expert's proposed approach — understand the trade-offs clearly enough to make an informed selection before the methodology itself becomes the issue.

The Three Methods at a Glance

Method 1: Time Impact Analysis (TIA)

TIA is a prospective methodology. It inserts a delay event into a schedule as it existed at the time of the delay, re-runs the network, and measures the resulting shift in completion date. It's asking, in effect: "Given what we knew at the time, what was the projected impact of this event on the projected finish?"

Strengths: TIA is contemporaneous in spirit — it uses the schedule as it existed at the moment the delay occurred, so it captures contractor intent and the critical path as actually understood at the time. It's the methodology most commonly specified in AACE International's Recommended Practice 29R-03. It's relatively clean for isolated, discrete delay events with clear trigger dates.

Weaknesses: TIA requires a clean, validated schedule at the moment of delay insertion. If the underlying schedule has logic flaws, optimistic durations, or phantom float (see our piece on buried schedule risks), the TIA projects impact into a network that doesn't reflect reality. Courts and arbitrators have become increasingly willing to reject TIA analyses that use baseline schedules never updated for known-at-the-time problems.

When it holds up: Single-event delays, clear cause-and-effect, good contemporaneous schedule records, experienced scheduler who can validate the network before insertion. TIA works especially well for change-order directives and differing site conditions — events with clear dates and clear scope.

When it gets torn apart: Multiple overlapping delays, weak schedule records, ambiguous cause-and-effect, or when the "impacted" schedule fails a basic DCMA-14 assessment at the insertion point. An expert who can't explain why the inserted fragnet integrates cleanly with the receiving schedule is in trouble.

Method 2: Windows Analysis

Windows Analysis breaks the project into sequential time periods ("windows") — typically monthly — and compares what was planned at the start of each window to what actually happened during it. Delays are identified window by window, with responsibility allocated based on what drove the critical path slippage in each specific period.

Strengths: Windows Analysis is the most analytically rigorous of the three methods. It captures delays chronologically, making it well-suited for multi-party disputes where responsibility shifts over time. It uses contemporaneous schedule updates, which means the analysis reflects what the project team actually believed and planned at each point. Courts tend to find it highly persuasive when done well, because the narrative tracks how the project actually unfolded.

Weaknesses: Windows Analysis is data-hungry. It requires clean monthly schedule updates throughout the project — and schedules that actually reflect progress rather than administrative updates that carry over unchanged activity durations. On projects with poor update discipline, Windows Analysis either becomes impossible or requires so much reconstruction that the methodology starts drifting toward as-built analysis territory. It's also the most expensive of the three methods to execute properly.

When it holds up: Long-duration projects with good monthly update records, multi-party delays, situations where responsibility allocation matters (e.g., concurrent delay scenarios), and cases where the opposing expert is likely to be well-credentialed. A well-executed Windows Analysis is difficult to dismantle because every conclusion is anchored in a specific contemporaneous schedule update.

When it gets torn apart: Weak update records, projects where monthly schedules were administratively rolled forward without real progress tracking, or cases where the window boundaries themselves can be argued to have been selected strategically. The methodology lives or dies on the quality of the underlying monthly schedules.

Method 3: Collapsed As-Built (But-For Analysis)

Collapsed As-Built is retrospective. It starts with the project's actual as-built schedule (what really happened), identifies the delay events attributable to one party, removes (or "collapses") those events from the timeline, and measures how early the project would have finished without them.

Strengths: Collapsed As-Built is conceptually intuitive — "here's what happened, here's what would have happened without their delays" — which makes it accessible to judges and juries. It doesn't require contemporaneous schedule updates because it works from as-built records, photographs, daily reports, and similar documentation. It can be constructed even when the underlying schedule discipline was poor, because the method doesn't depend on the original planning.

Weaknesses: This is where methodology selection most often goes wrong in construction litigation. Collapsed As-Built is inherently retrospective and therefore vulnerable to hindsight bias. The analyst chooses which events to "collapse," which decisions affect the final number materially. It also tends to produce unfalsifiable arguments — "without your delay, my project would have finished on this date" can be very hard to disprove without doing an entire competing analysis.

Well-funded opposing experts routinely attack Collapsed As-Built analyses on three fronts: (1) the selection of which events to collapse, (2) the assumption that remaining activities would have proceeded unaffected, and (3) the absence of contemporaneous evidence that the "but-for" sequence was ever actually achievable.

When it holds up: Projects with weak contemporaneous schedule records but strong documentation of actual events (photographs, daily reports, correspondence). Clear, isolated delay events. Cases where the collapsed timeline is conservatively constructed and the analyst explicitly addresses why the "but-for" assumptions are defensible.

When it gets torn apart: When the selection of collapsed events looks strategic. When the opposing side can demonstrate that removing the challenged events wouldn't have avoided delays caused by other factors. When the as-built records themselves are incomplete or contested. In my experience, the phrase "cherry-picked events" is the single fastest way for opposing counsel to begin dismantling a Collapsed As-Built analysis in front of a trier of fact.

The Methodology Selection Framework

The right method for a specific case is rarely ambiguous if the analyst applies a disciplined selection framework. The wrong method is usually chosen for one of three reasons: (1) the analyst's personal preference or familiarity, (2) the available data constraining the choice, or (3) a desire to produce a specific numerical outcome.

A defensible selection considers, in order:

1. When is the analysis being performed? If the claim is being pressed during live construction, TIA is the natural starting point. If it's mid-project and schedule records are good, Windows Analysis. Post-completion, Windows Analysis remains preferred if records support it, with Collapsed As-Built as a fallback only when they don't.

2. How clean are the contemporaneous schedule records? This is the constraint that most often dictates the practical choice. Good monthly updates enable Windows Analysis. Poor updates may force Collapsed As-Built. Mid-quality records may permit a hybrid approach.

3. What's the dispute structure? Single delay event with clear cause-and-effect points toward TIA. Multiple overlapping delays with responsibility allocation points toward Windows Analysis. Post-completion disputes with weak schedule discipline point toward Collapsed As-Built — carefully.

4. What will survive cross-examination? The best methodology on paper is the worst methodology in deposition if the underlying data doesn't support it. A TIA with a flawed baseline is worse than a conservatively executed Collapsed As-Built. A Windows Analysis with fabricated update integrity is worse than honest acknowledgement that the records are insufficient.

The discipline here is unglamorous but essential. The methodology should match the facts and the evidentiary posture, not the desired outcome.

The One Question Every Delay Expert Should Be Ready For

In my experience, the single most effective question I've seen opposing counsel ask a delay expert is this:

"Walk me through the three methodologies you considered for this analysis, and explain specifically why you chose the one you did over the other two."

An expert who can answer that question cleanly — acknowledging the alternatives, explaining the specific facts that made the chosen method appropriate, and addressing the weaknesses of the chosen method preemptively — has established credibility that the rest of the deposition will reinforce rather than erode.

An expert who can't answer it, or who gives a conclusory "this was the right method for the facts" without real analysis, has handed opposing counsel the rest of the day.

Methodology selection is not a throwaway decision. It's the foundation on which everything else rests.

A Note on Method Hybrids

Real construction delay cases frequently involve facts that don't align cleanly with any single methodology. A sophisticated analysis may combine elements — a Windows Analysis for the period with good records, supplemented by Collapsed As-Built analysis for the tail end where update discipline fell apart.

Hybrid approaches are defensible when the analyst explicitly describes what was done and why. They become problems when they're presented as a single methodology while actually being a patchwork. If you're combining methods, say so — and explain the rationale for each transition.

Why Methodology Selection Matters Before Retention

The attorneys and claim consultants who retain delay experts well tend to have a common pattern: they talk methodology with the expert candidate before engagement, not after. The conversation looks less like "what's your rate?" and more like "given the facts of this case, what methodology would you propose, and why?"

Experts who can answer that question crisply — with a specific methodology tied to specific facts — tend to be the experts worth retaining. Experts who default to their comfortable methodology regardless of the case facts tend to be the experts who create problems in deposition.

There's no universal right answer. But there's almost always a defensible selection for a given set of facts. The expert worth hiring is the one who can walk through the selection process out loud, consider the alternatives, and arrive at a choice that holds up under scrutiny.