Time Impact Analysis
Time Impact Analysis (TIA) is the preferred method for quantifying delay entitlement under NEC contracts and one of the most widely accepted methods in UK construction disputes. It involves inserting a delay event into the programme at the point it occurred and measuring the resulting impact on the Completion Date.
What is a Time Impact Analysis?
A TIA works by inserting a delay event into the programme at the point it occurred — using the Accepted Programme (or most recent updated programme) as the pre-impact baseline — and measuring how much, if at all, the event delays the forecast Completion Date. This gives the Contractor a transparent, programme-based entitlement figure that is easy for the PM, engineer, or tribunal to follow.
Prospective TIA — Used at the Time
The prospective TIA is carried out at the time the delay event arises — before the impact has fully unfolded. It is the preferred method under NEC because it aligns with the compensation event regime: the Contractor submits a quotation based on the forecasted impact, and the PM assesses and accepts (or disagrees) in real time. Deltime prepares prospective TIAs as part of CE management on live NEC projects.
Retrospective TIA — Used in Disputes
Where delays were not assessed prospectively — or where the Contractor's position is being defended or advanced in adjudication, arbitration, or litigation — a retrospective TIA is prepared after the fact. Deltime reconstructs the programme at each key delay event and models the impact, using contemporaneous records to justify each input.
Concurrent Delay & Apportionment
One of the most contested areas in TIA is concurrency — where Employer and Contractor risk events overlap in time. Deltime's TIA methodology addresses concurrency directly, applying the analysis framework applicable to the governing law and contract, and presenting a clear, defensible apportionment of delay responsibility.
Programme Inputs & Assumptions
A TIA is only as strong as the programme it uses as its baseline. Deltime reviews the Accepted Programme (or most recent update) for logic, float, and critical path integrity before inserting delay events — so the analysis is not undermined by a weak underlying programme.
TIA in Adjudication & Litigation
Deltime prepares TIA reports to a standard suitable for adjudication, arbitration, and expert witness use — with a full methodology note, assumption log, and audit trail from programme to conclusion. Every TIA is structured so that a decision-maker unfamiliar with the project can follow the logic from first principles.
Retrospective TIA — Commercial Development, London
Representative figures from a retrospective Time Impact Analysis prepared by Deltime for an adjudication on a JCT Design & Build contract.