Delay analysis methods compared: which one your records can support

Delay analysis proves element two of the four-element test every extension of time claim has to satisfy: causation. Below: a comparison of the methods, then a chooser, then the detail you need to defend the choice.

Delay analysis methods compared

The first six rows are the Protocol's six, in its order. The last two sit outside that list: the project-wide comparison at paragraph 11.7, and recreated updates (AACE MIP 3.5).

Stance, needs and the Protocol's own criticisms are read from the SCL Delay and Disruption Protocol, 2nd Edition (February 2017), paragraphs 11.5 to 11.7. The AACE pairings follow the published harmonisation discussed below. The cost ranking beyond what the Protocol states, and the strengths column, are opinion. (Opinion.)

Two things in that table surprise people. Collapsed as-built is a cause and effect method in the Protocol's own table, because the analyst starts from the delay events and removes them. And time impact analysis determines the critical path contemporaneously, which is what separates it from impacted as-planned.

Which method should I use?

Answer three questions in order: when are you doing the analysis, what programme and records exist, and what does the contract or the forum require. The Protocol's own list of selection criteria at paragraph 11.3 covers the same ground and adds proportionality (the value of the project or dispute), the nature of the events and the project, and the time available.

The same decision as a sequence:

1. Does the contract prescribe a method or a stance? If yes, that governs. Many US and Middle East EPC contracts name time impact analysis. (Opinion.)
2. Are you assessing contemporaneously or time-distant? While the works are live, the Protocol recommends time impact analysis (paragraph 11.4(a) and Core Principle 4). Once the assessment is after completion or long after the event, Core Principle 11 says the prospective analysis "may no longer be appropriate".
3. What does the record set actually contain? An accepted baseline with logic and calendars, a statused update series in native format, dated daily reports and RFI logs? The next section maps each combination to a method; the EOT claim readiness checklist walks through the items.
4. Is concurrency in issue? 29R-03's commentary is reported to treat MIPs 3.1 to 3.5 as generally inadequate for rigorous concurrency and pacing analysis without a modelled or split approach plus factual records. See concurrent delay.
5. Can you agree the method with the other side? Protocol paragraph 11.8 recommends agreeing a method before significant work on an after-the-event analysis, and says a failure to consult might be taken into account when the costs of the dispute are allocated.

If the filters leave nothing, what is left is a total time claim with no critical-path attribution, the kind of composite claim Core Principle 17 discourages. Advanced as a first resort it reads as a concession that the records were not kept. (Opinion.)

Which methods can your records actually support?

Work from the record set inward.

The last row is an inference from Core Principle 9, which says identification of float is greatly assisted by a properly prepared and regularly updated programme, and from paragraph 11.6, which warns that a method run without an accepted programme leaves greater scope for disagreement. (Inference.)

The loss of contemporaneous updates is the single largest evidential loss available on a construction project. It removes the dynamic methods in one move. (Opinion.) The Protocol's answer is Core Principle 1 and its guidance at paragraphs 1.3 and 1.5: agree the record regime, documented, before contract or at the outset of the works, covering the types of records, who produces and checks them, frequency, distribution, format, and ownership, storage and access. It is the only point at which the method question is genuinely open. The full record-category analysis sits in the records that decide whether you have a claim at all.

Where Storia fits

Most of the failures above share a cause: the record a method needs was never assembled, or cannot now be tied to a date. Storia turns drawings, RFIs, schedules, correspondence and field reports into one source-linked project record, where every answer traces back to the document it came from. It builds the project narrative as the work happens, so the contemporaneous record a delay analysis depends on is assembled while it is still contemporaneous, and teams can resolve a delay dispute in coordination or move from records to a claim-ready case in days. See claims and dispute resolution.

Prospective or retrospective: the hinge

The Protocol separates two questions that most writing collapses into one. Paragraph 11.4(d): criticality is determined prospectively (the view at the outset), contemporaneously (an evolving view) or retrospectively (the view from the end). Paragraph 11.4(e): delay impact is determined prospectively (the likely impact) or retrospectively (the actual impact on the as-built critical path), and the two may not match because actual performance was shaped by acceleration and re-sequencing.

The Protocol's Core Principles set the timing. Core Principle 4: do not "wait and see"; deal with the time impact of Employer Risk Events as the work proceeds. Core Principle 5: grant the extension to the extent the event is reasonably predicted to prevent completion by the then prevailing contract completion date. Core Principle 11 is the hinge: where the assessment happens after completion or significantly after the event, the prospective analysis referred to in the guidance to Core Principle 4 "may no longer be appropriate". Paragraph 11.4(a) adds that, time-distant, effect and cause methods "are generally considered to be more forensically reliable".

The choice of stance can move the day count. In Fluor Ltd v Shanghai Zhenhua Heavy Industry Co Ltd [2018] EWHC 1 (TCC) at [275] the court accepted expert evidence that a prospective analysis "does not necessarily produce the same answer as an analysis carried out retrospectively". It said the prospective approach is correct for awarding an extension of time, but that its own exercise, a damages claim, required some form of retrospective analysis. Compare Walter Lilly & Co Ltd v Mackay [2012] EWHC 1773 (TCC), where at [380] the debate was "sterile" because both delay experts accepted that each approach, done correctly, should produce the same result. The two are not in conflict: in Walter Lilly the point was common ground between the experts, and in Fluor it was not. (Inference.)

Where the contract picks a stance, it governs. NEC4 ECC clause 63.5 is prospective against the Accepted Programme. Under the JCT clause 2.25.1 in Mace Construct Ltd v Baltic Investment Holdings Ltd [2026] EWHC 976 (TCC), the Employer's extension is a prospective estimate, and at [50] an adjudicator reviewing it stands in the Employer's shoes and must carry out that prospective assessment rather than a purely retrospective one. Contracts that provide an end-of-job review can call for something different, so read the clause before choosing the stance.

The six methods, one by one

Each note adds to the comparison table what Protocol paragraph 11.6 says the analyst must do.

Impacted as-planned analysis

Fragnets go into a logic-linked baseline and the programme is recalculated. The analyst must first confirm the baseline is reasonable, realistic, achievable and properly linked, because nothing later corrects it. After the event, on a project that ran for months, it is the most exposed method there is. (Opinion.) AACE MIP 3.6.

Time impact analysis

Fragnets go into the Updated Programme current at each event, and the likely delay to the then predicted completion date is read off. The analyst must check that each update's history reflects actual progress, and watch for mitigation already built into it. AACE MIP 3.7.

Time slice windows analysis

The analyst verifies (or develops) a series of updated programmes, typically monthly, reads the critical path and critical delay in each slice, then searches the records for the cause. When the updates are sound, this is the strongest after-the-event position available. (Opinion.) AACE MIP 3.3, or MIP 3.4 where progress and non-progress revisions are split.

As-planned versus as-built windows analysis

Windows are framed by updates, milestones or significant events, and the critical path in each is found by a practical analysis of the facts rather than by software. The Protocol stresses that the analyst must set out how criticality was determined. Being fact-rooted, it is often the easiest method for a tribunal to follow. (Opinion.) AACE MIP 3.2.

Retrospective longest path analysis

The longest continuous path is traced backwards from actual completion through a verified as-built. The Protocol warns that this as-built critical path is not the contemporaneous critical path of the windows methods. It is rarely used. (Opinion.) No dedicated AACE MIP.

Collapsed as-built (but-for) analysis

Delay events are extracted from a logic-linked as-built to show what would have happened without them. Such a programme rarely exists, so logic usually has to be added, and that added logic is where every cross-examination starts. (Opinion.) It can be run in windows. AACE MIP 3.8 or 3.9.

Time impact analysis or impacted as-planned?

Both are cause and effect methods, both insert delay fragnets into a schedule and re-run CPM, and both determine delay impact prospectively. The difference is the base. Impacted as-planned inserts the fragnets into the original baseline, one base for every event, which is why AACE International RP 29R-03, Forensic Schedule Analysis (rev. 25 April 2011) classifies it as MIP 3.6, modeled / additive / single base. Time impact analysis inserts each fragnet into the programme as updated to that event's point of impact, a different base per event: MIP 3.7, modeled / additive / multiple base. In the Protocol's paragraph 11.5 table the same difference appears as the critical path being determined prospectively for one and contemporaneously for the other.

That distinction has a hard practical consequence: a project with no reliable contemporaneous updates cannot run time impact analysis at all. It is pushed down to impacted as-planned, the method with the lowest data requirement and the weakest reputation. The choice between MIP 3.6 and MIP 3.7 is very rarely a free one.

The 2nd edition changed the Protocol's position, and the change is under-reported. The introduction lists, among the key changes, that there is "no longer a preferred delay analysis methodology" where the analysis is carried out time-distant from the delay event. The 1st edition's preference for time impact analysis now survives only for contemporaneous assessment. Citing the Protocol as authority for running a time impact analysis years after completion is citing the superseded edition.

How the SCL methods map onto AACE 29R-03, and where they do not

They map, but they are not translations of each other, and the gaps run both ways. AACE 29R-03 has no dedicated method implementation protocol for the Protocol's retrospective longest path. The Protocol's six do not include MIP 3.4, the contemporaneous split, or MIP 3.5, recreated updates.

The MIP numbers and taxonomy strings are read from AACE's published table of contents for 29R-03. The pairings follow Anamaria Popescu (Ankura), Harmonizing SCL D&D2 and AACE 29R-03 (5 November 2025, first published by SCL International). The "no equivalent" rows are this page's reading of the gaps, not a published concordance. (Inference.)

Popescu's thesis: SCL supplies the strategic and principled frame, 29R-03 the technical protocol, and a competent expert uses both. Cite the AACE layers, not just the number. Observational methods examine the schedules as they are; modeled methods insert or extract delays and re-run CPM. Static or dynamic says whether the critical path is fixed or tracked as it shifts. Stating "MIP 3.3, observational / dynamic / contemporaneous as-is" tells a tribunal precisely what was done. Stating "a windows analysis" does not.

MIP 3.4 isolates non-progress revisions (logic changes, calendar changes, re-sequencing) from actual progress variance, which is the separation a concurrency argument needs. And 29R-03 is not the whole of AACE's claims guidance: AACE International RP 130R-23, Demonstrating Entitlement to Cumulative Impact Claims in Construction (15 May 2023) covers the cumulative-impact side and is frequently missed.

Is a named method a rule of law?

No. The Protocol says so itself: its introduction states that it is not intended to be a contract document and does not purport to be a statement of the law. Courts in three common-law jurisdictions have taken the same line in different ways, and none treats the SCL Delay and Disruption Protocol or AACE 29R-03 as binding.

All first instance; no appellate authority on method choice was located. How White Constructions and Santos v Fluor sit together is set out on delay analysis methods in Australia.

In Thomas Barnes one expert had run as-planned versus as-built windows and the other a hybrid of time slice windows and time impact analysis. At [109] the judge declined to attach much importance to whether each had "loyally followed" his method, relying on the Protocol's own paragraph 11.2: the conclusions must be "sound from a common sense perspective".

No reported judgment was located deciding a case on "float suppression" as a named doctrine. NEGATIVE FINDING Artificial constraints, excessive lags and quiet baseline re-sequencing are real, but they operate as an evidential and credibility attack, not a cause of action.

The convergent rule across every forum: pick the method the records support, state the taxonomy label, state the assumptions, and explain every departure from the named method. (Opinion.)

What tribunals actually punish

Data quality, not method choice. A modest windows analysis on clean statused monthly updates beats an orthodox analysis on reconstructed or re-logicked schedules. (Opinion.)

Alares Construction, Inc. v Department of Veterans Affairs, CBCA 6149, 7071, 7597 (21 March 2025) shows what that costs. Alares asserted that the VA caused all 765 days of delay and sought extended general conditions for 653 of them. The Board worked through four periods and found the VA responsible for 218 days of critical path delay, with Alares responsible for the rest. The contract required monthly schedule updates and a revised schedule whenever the schedule stopped representing actual progress. In one period Alares' schedule update introduced a new logic that took its own late concrete slab off the critical path; the Board said that explanation and Alares' "sudden revision of logic make no sense and ignore or sugarcoat the impact of delays for which Alares is responsible."

The older US authority is to the same effect. In George Sollitt Construction Co. v United States, 64 Fed. Cl. 229 (2005) the contract required a baseline within fifteen days of award and monthly updates. The baselines arrived months late, no updates were provided for the start-up and completion phases, and some critical path activities were reported only as percentage complete, which the court noted is not standard industry practice. None of that is about the technique the expert selected. It is all about the contemporaneous record the technique was run on.

Under NEC4 ECC the assessment stands or falls on the Accepted Programme, and nobody can invent one. In Premier Modular Ltd v Maidstone and Tunbridge Wells NHS Trust [2026] EWHC 1404 (TCC) it was common ground that the Project Manager never accepted a later programme; the adjudicator's finding that it had been updated, which neither party argued, was one of the natural justice grounds that defeated summary enforcement.

Which edition are you citing?

Cite both frameworks with their dates, every time. As at September 2026 the SCL Delay and Disruption Protocol is in its 2nd Edition, February 2017, which supersedes the 1st edition (October 2002) and Rider 1. AACE International RP 29R-03, Forensic Schedule Analysis, stands at rev. 25 April 2011.

AACE 29R-03. A draft revision circulated around 2023, and no published revision has been located, but AACE's member catalogue was not accessible for this page: check the AACE library before citing the revision date in an expert report. SCL Protocol. No 3rd edition has been located on the SCL site or in 2025–26 commentary. High confidence, not certainty.

Frequently asked questions

What are the main delay analysis methods?

The SCL Protocol, 2nd Edition (February 2017), tabulates six commonly used methods at paragraph 11.5: impacted as-planned, time impact analysis, time slice windows, as-planned versus as-built windows, retrospective longest path and collapsed as-built. AACE RP 29R-03 classifies nine method implementation protocols, adding a split windows method (MIP 3.4) and recreated updates (MIP 3.5). The Protocol also mentions time chainage, line of balance, resource curve and earned value analysis.

What is the difference between time impact analysis and windows analysis?

Time impact analysis models the likely effect of an event by inserting a fragnet into the programme updated to that date: cause and effect, delay impact determined prospectively. A windows analysis measures the delay that actually occurred in each period and then looks for its cause: effect and cause, delay impact determined retrospectively. Time impact analysis suits assessment during the works; windows methods suit analysis after the event.

Can you do a time impact analysis after the project is finished?

You can, but the Protocol no longer prefers it for time-distant analysis, and Core Principle 11 says the prospective approach may no longer be appropriate once the assessment is after completion. A tribunal will ask why actual progress was ignored.

Which delay analysis method do courts prefer?

None as a matter of law. The English TCC in Thomas Barnes (2022) held experts are not confined to one of the SCL methods; what matters is that the method suits the facts and the records and that departures are explained. Tribunals punish poor records and unexplained logic changes far more often than a method choice.

Is the SCL Delay and Disruption Protocol binding?

No. It says it is not a contract document or a statement of the law, and it gives way to the contract and governing law. It is widely treated as good-practice guidance, and in Australia one court has reportedly adopted referees' findings that preferred the expert who followed it more closely. A contract can make a method binding by naming it.

Next steps

If the analysis is going into a claim, how to write an EOT claim shows where it sits and what it must prove, and the EOT claim readiness checklist tests whether the records will carry the method you picked. If the delay is still unfolding, the analysis comes second to the notice: delay notice templates for AS 4000, FIDIC 2017 and CCDC 2 and notice and time bars cover what to send and by when. The money side of a proven delay is on prolongation and delay costs.

About this material Library content is general information about construction claim practice, not legal advice. Entitlement, deadlines and procedure are governed by your own contract and by the law of the place the work is performed. Reviewed October 6, 2026 · Report a correction