What is the SCL Protocol?
The SCL Delay and Disruption Protocol is a guidance document published by the Society of Construction Law that sets out best practice for the analysis of delay and disruption in construction projects. It is not a contract term — it has no legal force unless incorporated by reference — but it is widely treated as authoritative guidance by adjudicators, arbitrators and the courts.
Delay experts who deviate from the Protocol without good reason face hard questions in cross-examination. Parties whose claims are structured in accordance with the Protocol are taken more seriously. In practice, the Protocol sets the standard against which delay analyses are measured.
Key change 1: Concurrent delay
The treatment of concurrent delay was one of the most contested issues in construction law at the time of the first edition. The second edition brings greater clarity — though it stops short of resolving the legal debate definitively.
The Protocol now distinguishes between two scenarios:
- True concurrency — where both an Employer Risk Event and a Contractor Risk Event are causing critical delay in the same period, and both would independently have caused delay to completion.
- Sequential delays that overlap — where delays from both parties occur in the same period but are not truly concurrent on the critical path.
For true concurrency, the Protocol recommends that the contractor should receive an extension of time but no prolongation costs. This reflects the Malmaison approach in English law. However, the Protocol acknowledges that the legal position varies by jurisdiction and that the contract terms must be examined carefully.
SCL Protocol, Guidance Note 11: "If [true concurrent delay] is established, then [...] the Contractor is entitled to an EOT but he may not be entitled to recover prolongation costs for the period of concurrent delay."
Key change 2: Preferred delay analysis method
The first edition identified several delay analysis methods without clearly preferring any of them. The second edition is more directive: it identifies prospective Time Impact Analysis as the preferred method where it is practical, while acknowledging that retrospective methods may be necessary when the analysis is being prepared after the event.
For retrospective analysis, the Protocol provides a clearer hierarchy: time impact analysis remains preferred even retrospectively, followed by the "windows" approach, with the collapsed as-built method reserved for cases where other methods are not possible.
The practical effect is significant. An expert who has used a collapsed as-built method when TIA was feasible will now be required to justify that choice. Parties should specify in their contracts which analysis method is required.
Key change 3: Disruption claims
The second edition gives significantly more attention to disruption — the loss of productivity that results from an Employer Risk Event, distinct from delay to completion. This reflects the increasing prominence of disruption claims in major projects.
The Protocol endorses several methods for quantifying disruption, including the measured mile approach (comparing productivity in disrupted and undisrupted periods), the project comparison method, and programme analysis. It cautions against the use of industry productivity factors (such as those published by MCAA or NECA) without site-specific corroboration.
Key change 4: Contemporaneous records
The second edition places much greater emphasis on contemporaneous records as the foundation of any delay or disruption claim. The Protocol now explicitly states that both parties should keep adequate contemporaneous records, and that the failure to do so will disadvantage the party that fails.
For contractors, this means: daily site diaries, resource records, progress photographs, weather records, RFI logs, instruction registers, and programme updates. For employers, it means: instruction records, design issue logs, and records of access restrictions.
Key change 5: Global claims
The second edition takes a firmer stance on global claims — claims that aggregate multiple delay events without attributing a specific quantum to each. The Protocol states clearly that global claims are unlikely to succeed: a contractor cannot simply say "all of these events together caused us £X of additional cost" without demonstrating the causal link between each event and a defined portion of the claimed loss.
This reflects the courts' increasing scepticism about global claims following cases such as John Doyle Construction v Laing Management and Walter Lilly v Mackay.
What this means in practice
For construction lawyers and claims consultants, the practical implications of the second edition are clear:
- Structure your delay analysis as a TIA wherever possible — even retrospectively
- Address concurrent delay explicitly and demonstrate that you have considered it
- Build disruption claims on measured mile or site-specific productivity data, not industry factors
- Ensure your clients are keeping adequate contemporaneous records from day one
- Avoid global claims — attribute each loss to a specific event
SCL-compliant reports in minutes
Every PlanLens report is structured in accordance with the SCL Protocol 2nd Edition — court-ready from the moment it is generated.