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Society of Construction Claims Specialists International
SCL Protocol 2nd Edition
The Society of Construction Law Delay and Disruption Protocol 2nd Edition (February 2017) is the leading UK methodology guide for handling delay and disruption claims on construction projects. Unlike the contract-form visuals in this series (401 to 410), the Protocol is not a contract but a set of recommended best practices. The visual covers its structure (Guidance Part A definitions, Part B Core Principles, plus numbered Sections 1 to 22), its treatment of float at Core Principle 8, its concurrent-delay position at Section 10, and the six methodologies of forensic delay analysis set out at Section 11.5.
The SCL Protocol 2nd Edition: Core Principles, Float, Concurrent Delay, and the six delay-analysis methodologies
0 of 8 sections explored
01
The Protocol: what it is, what it is not, and why the 2nd edition was needed
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The Society of Construction Law Delay and Disruption Protocol is a methodology guide, not a contract. It sets out recommended best practice for dealing with delay and disruption on construction projects and is the most widely-cited UK reference document on delay analysis in international practice.
The Protocol is structured in two Guidance Parts plus numbered Sections. Part A contains definitions of delay, disruption and acceleration. Part B sets out the Core Principles. The Sections (1 to 22) develop the Core Principles in detail. Practitioners typically quote the Protocol by Core Principle number (e.g., "Core Principle 4") or by Section number (e.g., "Section 10.4").
1
Publication history. The 1st edition was published in October 2002. Rider 1 to the 1st edition was issued in July 2015. The 2nd edition, published in February 2017 following a ten-year review, superseded both the 1st edition and Rider 1 and remains the current version.
2
Not a contract. The Protocol expressly disclaims any intent to state the law. The 2nd edition dropped the 1st edition's model clauses and no longer suggests the Protocol should be incorporated into the contract. It is guidance on good practice; the underlying contract controls the legal position.
3
Why the 2nd edition. Three principal drivers: the 1st edition's strong preference for Time Impact Analysis was being misused in disputes where the analysis was done long after the delay; delay-analysis techniques used in practice had widened beyond the list in the 1st edition; and the concurrent-delay guidance in the 1st edition had not kept pace with subsequent UK case law.
4
Principal areas of change. Sections 1 (records), 4 (contemporaneous assessment, discouraging "wait and see"), 10 (concurrent delay), 11 (retrospective delay analysis, now with six methodologies), and 18 (disruption). The 2nd edition is materially more balanced between Contractor and Employer than the 1st.
The Protocol's authority is persuasive, not binding. Its value lies in being a common reference point that construction professionals, lawyers, and tribunals recognise. Where a dispute arises, both sides will typically cite the Protocol even if they disagree on its application to the facts.
The Protocol addresses methodology, not contract allocation; contract wording always takes precedence over the Protocol where the two diverge
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02
The Core Principles: the Protocol's headline guidance
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The Core Principles in Guidance Part B are the Protocol's most cited component. Each is a one-line statement of good practice, developed in the corresponding numbered Section of the Protocol. The principles that matter most for float, EOT and concurrent delay sit in the following Core Principles.
The Core Principles listed above are the headline statements. Each is developed in a corresponding numbered Section of the Protocol (Sections 1, 2, 4, 10, 18, and related parts). Practitioners should cross-reference Core Principle number to Section number when citing the Protocol in correspondence or submissions.
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Core Principle 1 - Programme and records. The Contractor should prepare and maintain a properly developed programme showing the manner and sequence in which the works will be carried out. The Employer and its agents should allow a proper amount of time in the programme for review, comment and acceptance where this is required.
2
Core Principle 2 - Purpose of EOT. The benefit of the right to an EOT is that the Contractor will be relieved of the consequences of Employer Delay to Completion, such as liquidated damages for delay, and will have a reasonable time to complete the Works.
3
Core Principle 4 - Effect on the then prevailing contract completion date. An EOT should be granted to the extent that the Employer Risk Event is reasonably predicted to prevent the works from being completed by the then prevailing contract completion date. This is the Protocol's core test for entitlement to time.
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Core Principle 8 - Float. Unless there is express provision to the contrary in the contract, where there is remaining total float in the programme at the time of an Employer Risk Event, an EOT should only be granted to the extent that the Employer Delay is predicted to reduce to below zero the total float on the critical path affected by the Employer Delay to Completion. This is the Protocol's first-come-first-served rule.
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Core Principle 10 - Concurrent delay. True concurrent delay is the occurrence of two or more delay events at the same time, one an Employer Risk Event, the other a Contractor Risk Event, and the effects of which are felt at the same time. Where Contractor Delay to Completion occurs or has an effect concurrently with Employer Delay to Completion, the Contractor's concurrent delay should not reduce any EOT due.
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Core Principle 20 - Disruption. Disruption (as distinct from delay) is a disturbance, hindrance or interruption of the Contractor's normal working methods, resulting in lower efficiency. Disruption claims relate to loss of productivity in the execution of particular work activities, which may or may not delay completion.
Core Principle 4 (EOT to the prevailing contract completion date) and Core Principle 8 (float first-come-first-served) together define the Protocol's substantive float position. These are the two principles that map onto the absorption mechanic used across visuals 401 to 410.
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03
Float under the Protocol: Core Principle 8 and the first-come-first-served rule
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The Protocol's treatment of float is expressed in Core Principle 8 and developed in the related Section of the Protocol. The rule is one of the most quoted provisions in the 2nd edition because it resolves a point on which the 1st edition's guidance was ambiguous.
The text of Core Principle 8, paraphrased: unless there is express provision to the contrary in the contract, where there is remaining total float in the programme at the time of an Employer Risk Event, an EOT should only be granted to the extent that the Employer Delay is predicted to reduce to below zero the total float on the critical path affected by the Employer Delay to Completion.
Commentator criticism of Core Principle 8 (notably in published SCL papers commenting on the 1st edition before the 2nd was issued) argues the rule is unfair to Contractors because it allows early Employer-risk events to consume contingency the Contractor priced into the tender. That criticism notwithstanding, Core Principle 8 remains the Protocol's stated position in the 2nd edition.
A
Project-owned float, first-come-first-served. The Protocol's float position is that float is a project resource. Whichever delay first consumes the float takes the benefit, regardless of fault. This is the orthodox UK position and is consistent with US practice under AACE 29R-03 and ANSI/ASCE/CI 67-17 §5.2.
B
Critical-path test. The Core Principle 8 rule works by reference to the critical path affected by the Employer Delay. EOT is granted only for the portion of the delay that pushes the critical path past the prevailing contract completion date. Float absorption below zero is the trigger.
C
Contract override. The Core Principle opens with "Unless there is express provision to the contrary in the contract". Where the contract expressly allocates float to one party (for example, NEC4 ECC Clause 63.5 preserves terminal float for the Contractor; GC21 Edition 2 practice guide states "float belongs to the contractor"), the Core Principle does not displace that allocation.
D
Contractor duration contingencies are a different matter. The Protocol treats time risk allowances the Contractor has built into individual activity durations as distinct from float at the programme level. Such contingencies are the Contractor's; float at the network level is the project's.
The Protocol's Core Principle 8 is consistent with the EOT wording in AIA A201, JCT SBC 2024, FIDIC 1999 / 2017, CCDC 2, CCDC 14, AS 4000, AS 2124, and ConsensusDocs 200 (all silent on float, producing first-come-first-served outcomes). It is inconsistent with the NEC4 ECC Clause 63.5 structural preservation of terminal float, and sits in tension with the GC21 Edition 2 practice-guide statement that "float belongs to the contractor".
The "express provision to the contrary" escape hatch is load-bearing. Parties seeking a different float allocation must write it into the contract; reliance on commercial practice or general industry understanding is insufficient
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04
Section 10: concurrent delay under the 2nd edition
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Concurrent delay is one of the three substantive areas most materially revised in the 2nd edition. Section 10 of the Protocol sets out the definition and the recommended approach.
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Definition (Section 10.3 / Core Principle 10). "True concurrent delay is the occurrence of two or more delay events at the same time, one an Employer Risk Event, the other a Contractor Risk Event, and the effects of which are felt at the same time." True concurrent delay is rare; the label is often misused for events that are merely sequential.
2
Both delays must affect the critical path. The Protocol's position is that concurrent delay only arises where each of the Employer Risk Event and the Contractor Risk Event is an effective cause of Delay to Completion. If one of the delays is on a non-critical activity, the two are not concurrent for the purpose of the Protocol's analysis.
3
Time effect: concurrent Contractor delay does not reduce EOT. Where Contractor Delay to Completion occurs or has an effect concurrently with Employer Delay to Completion, the Contractor's concurrent delay should not reduce any EOT due. This is the Protocol's central concurrent-delay rule and is consistent with the traditional English prevention-principle position.
4
Money effect: apportionment. The Protocol recommends that compensation for prolongation be apportioned between the two concurrent causes. The Contractor recovers the share of prolongation attributable to the Employer Risk Event; it does not recover for the share attributable to its own concurrent delay.
5
Different timing of start is not concurrency. The Protocol (Section 10.10) treats delays that start on different days as non-concurrent, even if their effects overlap. This is a narrower view than some US authorities take. UK case law on this point is not uniform; the Protocol acknowledges the debate but adopts the narrower position.
The Protocol's concurrent-delay position is not universally accepted. English Court of Appeal authority (the well-known 2018 JCT concurrent-delay exclusion decision) has upheld contract terms that expressly exclude the Protocol's position, allowing parties to contract out of the "no reduction of EOT" rule. The Protocol itself acknowledges that its guidance can be displaced by contract drafting.
True concurrent delay is rare in practice; many claims that plead concurrency on the facts are actually sequential delays. Expect the opposing expert to attack the concurrency premise first.
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05
Section 11: the six delay-analysis methodologies
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The 2nd edition's Section 11 is one of the most pedagogically useful parts of the Protocol. It removes the 1st edition's preference for Time Impact Analysis in retrospective delay analysis and lists six methodologies, each with the question it answers, the type of analysis, the timing of the critical-path determination, and the records required. The summary table at paragraph 11.5 is the key reference.
The 2nd edition's key position is that no one method is preferred for retrospective analysis. Choice of method depends on the records available, the nature of the delay events, the complexity of the programme, and the purpose of the analysis. Tribunals and experts should select the method that best suits the factual matrix, not apply a default.
1
Impacted As-Planned Analysis. Cause and effect; critical path and impact determined prospectively. Asks: what effect would this event have had on the completion date assuming everything else went exactly as planned? Requires a logic-linked baseline programme and a selection of delay events to model.
2
Time Impact Analysis. Cause and effect; critical path determined contemporaneously, impact prospectively. Asks: what was the likely effect of this event on the completion date adjudged from the point in time when it was instructed or arose? Requires baseline plus update programmes or progress information plus events to model.
3
Time Slice Windows Analysis. Effect and cause; critical path determined contemporaneously, impact retrospectively. Asks: what was the contemporaneous or actual critical path to completion throughout the works and what were the causes of delay thereto? Requires baseline plus update programmes or progress information.
4
As-Planned versus As-Built Windows Analysis. Effect and cause; critical path contemporaneously, impact retrospectively. Same question as Time Slice but constructed differently: requires baseline programme and as-built data rather than contemporaneous updates.
5
Retrospective Longest Path Analysis. Effect and cause; both critical path and impact determined retrospectively. Asks: what was the as-built critical path to completion, viewed retrospectively, and what were the causes of delay thereto? Requires baseline and as-built programmes.
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Collapsed As-Built Analysis. Cause and effect; both retrospective. Asks: but for the event, when would the completion date have been achieved? Requires a logic-linked as-built programme and events to model. This method is sometimes called Modified As-Built or But-For Analysis.
Time Impact Analysis remains preferred for prospective or contemporaneous analysis done during the project; but for retrospective analysis done after the event, the Protocol now treats the six methods as equally available subject to suitability for the facts and records.
Expert witnesses using a methodology not supported by the available records open themselves to cross-examination; method choice should be justified by the record base, not by preference
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06
Sections 1 and 4: records and contemporaneous assessment
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The 2nd edition elevated two topics to particular prominence because the first edition's experience showed they were the weak points of most disputes: record keeping (Section 1) and the timing of EOT assessment (Section 4).
A
Section 1 - Records. The Protocol recommends that parties agree a record-keeping regime at the start of the project. Typical records include programme and progress records (updated baselines, logic and activity data, progress reports), cost records (labour, plant, materials), and correspondence (instructions, notices, meeting minutes). The 2nd edition lists the categories with more granularity than the 1st edition.
B
Section 4 - Contemporaneous assessment. The 2nd edition elevates the timely assessment of EOT claims to a Core Principle and discourages the "wait and see" approach where the Owner or Architect defers decision on an EOT claim until the overall impact is known. The Protocol's position is that EOT claims should be assessed as close to the event as possible, typically using Time Impact Analysis, and that any later adjustment should be made by way of review rather than by deferring the initial decision.
C
Why it matters for float disputes. Where an Employer-risk event consumes float early in the programme, a prompt Time Impact Analysis would show the reduction of float to below zero (or not) at the time of the event. Without contemporaneous records and assessment, the parties are forced into a retrospective reconstruction in which the original critical path is often disputed.
D
Impact on Section 11 methodology choice. The quality of records determines which of the six Section 11 methodologies is available. A project with weak contemporaneous updates may be limited to Retrospective Longest Path or Collapsed As-Built analysis; a project with good updates can use Time Slice Windows or As-Planned versus As-Built Windows, which the Protocol generally regards as more reliable.
The 2nd edition's emphasis on records and contemporaneous assessment is the most practical change from the 1st. It reflects the disputes experience of the decade between 2002 and 2017: most cases fail on evidence, not on principle.
Agreeing a record-keeping regime at the start of the project (per Section 1) is a low-cost insurance against later EOT disputes; the Protocol now treats it as a Core Principle
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07
The SCL Protocol compared with AACE 29R-03 and ANSI/ASCE/CI 67-17
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The three major industry-level guidance documents on delay analysis are the SCL Protocol, AACE International Recommended Practice 29R-03 (Forensic Schedule Analysis), and ANSI/ASCE/CI Standard 67-17 (Schedule Delay Analysis). They sit in different jurisdictions and have different legal status, but they converge on the core principles.
On the substantive float rule (project-owned, first-come-first-served absent express contract language), all three converge. On concurrent delay, the Protocol's narrow "same-day start" position differs from the broader US position in RP 29R-03; ANSI/ASCE/CI 67-17 takes a middle view. On methodology, the three lists overlap heavily but RP 29R-03 has the longest menu (nine methods) and the Protocol has the clearest pedagogical table (six methods with the question each answers).
SCL Protocol 2nd Edition (2017)
UK-centred; international readership. Part A definitions plus Part B Core Principles plus numbered Sections 1 to 22. Six methodologies at Section 11.5. Florida first-come-first-served at Core Principle 8. Concurrent-delay rule at Core Principle 10: Contractor concurrent delay does not reduce EOT, but prolongation cost is apportioned.
AACE RP 29R-03 (2011)
US-centred. Nine methodologies, more technical and tabulated. Covers cause-and-effect vs effect-and-cause theories in detail. Treats float as project-owned where contract is silent. Extensive commentary on near-critical paths and concurrent-delay theories (literal, functional, simultaneous).
ANSI/ASCE/CI 67-17 (2017)
US national standard, more formal status than the Protocol or RP 29R-03. Chapter 5 Section 5.2 states expressly: "In the absence of contract language shifting float 'ownership,' float is owned by the project. This means that float goes to the first party to use it." Concurrent delay defined narrowly (both delays must be on the critical path).
For a UK or international project, the Protocol is the primary reference; for a US project, ANSI/ASCE/CI 67-17 is the standard and RP 29R-03 is the detailed technical guide. A practitioner working across jurisdictions should know all three.
None of the three documents has binding legal force; they are persuasive guidance. Contract terms and applicable law always control where they diverge from the guidance
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08
In plain terms: how to use the Protocol in practice
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The Protocol is only as useful as the discipline with which it is applied. Practitioners, experts and tribunals cite it in most UK-based delay disputes; parties who follow its guidance from the start of the project typically find that later claims are easier to make out and harder to contest.
Seven practical habits make the Protocol work on a real project.
1
Agree a record-keeping regime at the start (Core Principle 1, Section 1). Programme baselines, progress updates, delay registers, correspondence, photographic records, cost records. Both sides benefit; the Contract Administrator should propose this at the first progress meeting.
2
Maintain the baseline programme and update it (Core Principle 1, Section 2). The Protocol expects logic-linked programmes updated with actual progress. Without that, the Section 11 methodologies have no data base to work against.
3
Assess EOT contemporaneously (Core Principle 4, Section 4). Discourage "wait and see". Submit Time Impact Analysis at the time of the event. Review later if circumstances change.
4
Treat float as project-owned unless the contract says otherwise (Core Principle 8). Plan for the first-come-first-served outcome. Where bespoke allocation matters, negotiate it into the Supplementary or Particular Conditions before signature.
5
Reserve concurrent-delay arguments (Core Principle 10, Section 10). True concurrent delay is rare. Most pleaded concurrency is actually sequential. Where concurrency is genuine, the Protocol's rule is that Contractor concurrent delay does not reduce EOT but apportions prolongation cost.
6
Pick the Section 11 methodology that fits the records. Do not default to Time Impact Analysis in retrospective analysis. Match the method to the records available: Time Slice Windows and As-Planned v As-Built Windows if the baseline and updates are good; Retrospective Longest Path or Collapsed As-Built if records are thinner.
7
Separate disruption from prolongation (Core Principle 20, Section 18). Disruption is loss of productivity, not delay to completion. Disruption claims are often made weaker by conflation with delay claims; the 2nd edition gives detailed methodology for measured-mile, earned-value, and industry-benchmark approaches to disruption quantification.
The 2nd edition's most practical message is that delay disputes are won or lost on records and contemporaneous assessment. The substantive principles (Core Principles on float, EOT, concurrent delay, disruption) are useful framing, but the day-to-day discipline of keeping records and assessing claims early determines outcomes.
The Protocol is not law. It is guidance. Citing it does not win a case; applying it consistently from the start of the project makes a case easier to win
The February 2017 2nd edition remains the current version of the Protocol. It supersedes both the 1st edition (October 2002) and Rider 1 (July 2015), and has not been reissued since.
Live Schedule Simulation
Core Principle 8 in action: float as a project resource
An eight-week construction sequence runs to a planned finish two weeks ahead of the prevailing contract completion date. Inject a small Employer Risk Event that is absorbed within float (no EOT under Core Principle 8), or a larger one that reduces float below zero (EOT to the extent of the breakthrough).
Activities
Project float
Project float
Planned finish
Completion Date
Planned finish
Wk 8
Completion Date
Wk 10
Remaining float
2 wks
Extension certified
0 wks
Baseline. The Contractor plans to finish at week 8. The prevailing contract completion date is week 10. The two-week gap is project float. Click Inject 1-week event to see an Employer Risk Event absorbed within float (no EOT under Core Principle 8), or Inject 3-week event to see one that reduces float below zero.
Critical-path activity
Employer Risk Event
Project float
Planned finish
Completion Date
Legal Disclaimer
This interactive process flow is provided for educational and professional development purposes only and does not constitute legal advice. The content reflects interpretations and analyses that may not apply to specific circumstances. Contract interpretation depends on specific wording, jurisdiction, and factual context. Always consult qualified legal professionals before making decisions based on this content. SCCSI and its contributors accept no liability for reliance on this material.
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