When a construction project falls into delay, the question is rarely whether the completion date has moved — everyone can see that it has. The real question is why it moved, who is responsible, and how much extension of time (EOT) the contractor is entitled to. Answering those questions credibly requires a recognised delay analysis method, applied properly to reliable programme data.
At Logic Line Consultancy we prepare and defend delay analyses on projects across the UAE and UK. In this article we compare the main methods described in the Society of Construction Law (SCL) Delay and Disruption Protocol, explain when each is appropriate, and highlight the factors that should drive your choice.
Prospective vs retrospective analysis
Before choosing a method, understand the fundamental split. A prospective analysis predicts the likely effect of a delay event at (or close to) the time it occurs, using the programme current at that date. A retrospective analysis looks back after the delay has unfolded and measures what actually happened, using as-built records. Contracts administered contemporaneously — as FIDIC intends — generally favour prospective assessment at the time of the event, while disputes decided long after completion often demand a retrospective, evidence-based view.
The main methods compared
1. Impacted As-Planned
Delay events are modelled as activities and inserted into the baseline programme; the movement of the completion date is taken as the delay. It is quick and cheap, but it ignores actual progress and any contractor culpability, which is why tribunals treat it with caution. It is most defensible very early in a project, when the baseline still reflects reality.
2. Time Impact Analysis (TIA)
The delay event is impacted onto a progress-updated programme reflecting the status of the works immediately before the event. TIA is the method the SCL Protocol recommends for assessing EOT contemporaneously, and it is widely used under FIDIC-based contracts in the Gulf. Its credibility depends heavily on the quality of the updated programme — if progress updates were not maintained, the analysis inherits that weakness.
3. As-Planned vs As-Built
The planned and as-built programmes are compared window-free, and the differences are explained by reference to the events on the record. It is intuitive, transparent, and works even where programme updates are poor — but it relies on the analyst’s reasoning to establish causation rather than a calculated model.
4. Windows / Time Slice Analysis
The project is divided into windows (often monthly, matching the update cycle). Critical path movement is measured window by window and attributed to the events active in each period. Many practitioners regard a well-executed windows analysis as the most robust retrospective method, because it tracks the actual critical path as it shifted over time. It does, however, require consistent, reliable progress updates for the whole period analysed.
5. Collapsed As-Built (But-For)
Employer delay events are removed from a verified as-built programme to show when the contractor would have finished “but for” those events. It is powerful in the right circumstances, but building a fully logic-linked as-built programme is laborious and the method is sensitive to the logic assumptions the analyst introduces.
How to choose the right method
- Timing: assessing an EOT during the project points towards TIA; a dispute after completion points towards windows or as-planned vs as-built.
- Records: reliable, regular programme updates enable TIA or windows analysis; sparse records may leave as-planned vs as-built as the only credible option.
- The contract: some contracts and schedules of amendments prescribe the method — check before you start, not after.
- Proportionality: the cost of the analysis should match the value at stake. A collapsed as-built on a minor variation claim helps no one.
- The audience: an Engineer assessing a claim contemporaneously expects a different product from an arbitral tribunal weighing expert evidence.
The common thread: records
Every method stands or falls on the underlying records — baseline and updated programmes, progress reports, site diaries, correspondence, and notices. The strongest analysis in the world cannot survive a baseline that was never approved or updates that were never issued. If you improve one thing on your next project, make it the discipline of your programme updates.
How Logic Line Consultancy can help
We prepare forensic delay analyses for claims and disputes, advise on the right method for your circumstances, and — better still — set up the planning and records regime that makes future claims easy to prove. If you are facing a delay issue on a project in the UAE, UK, or wider region, get in touch for an initial discussion.