SCL and AACE Delay Protocols: What Are They and How Do They Differ?

First in a short series on delay analysis, methodology and professional judgement

I am often asked about the difference between the Society of Construction Law Delay and Disruption Protocol and AACE Recommended Practice 29R-03: Forensic Schedule Analysis.

Do they say the same thing? Do they agree on delay analysis methodologies? Does one take precedence over the other? And, perhaps most importantly, how should they be used in practice when analysing delay on real construction projects?

These are sensible questions. Both documents are frequently referred to in extension of time claims, delay analysis, expert reports, arbitration proceedings and project advisory work. However, they are not identical documents and they are not trying to do exactly the same thing.

This article is the first in a short series looking at the two documents side by side. In this first article, I consider what each document is, what it is intended to do, and why the distinction matters. Later articles will look at specific topics including delay analysis methodologies, float, concurrency, disruption, acceleration, records and the role of professional judgement.

Two important documents, but different purposes

The starting point is that the SCL Protocol and AACE Recommended Practice 29R-03 should not be seen simply as competing delay analysis manuals. They are both valuable, but they serve different purposes.

The SCL Delay and Disruption Protocol is broader in scope. Its object is to provide practical guidance on common delay and disruption issues arising on construction projects, particularly where one party seeks an extension of time or compensation for additional time and resources. It is concerned with the management and resolution of delay and disruption issues, and with avoiding or limiting disputes where possible.

The AACE Recommended Practice 29R-03 is more specifically directed towards forensic schedule analysis. Its stated purpose is to provide a unifying reference of technical principles and guidelines for the application of Critical Path Method scheduling in forensic schedule analysis. It focuses heavily on the classification, selection and implementation of delay analysis methods.

Put simply, the SCL Protocol is more concerned with the wider contractual and practical management of delay and disruption, while AACE Recommended Practice 29R-03 is more concerned with the technical mechanics of forensic schedule analysis.

That distinction is important.

What is the SCL Delay and Disruption Protocol?

The SCL Protocol is probably the more familiar document to many practitioners in the UK and in common law influenced international markets. Although it is often referred to in disputes, it is not intended to be a contract document, nor does it purport to take precedence over the express terms of the contract or the governing law. The Protocol itself makes clear that it must be considered against, and give way to, the contract and governing law.

Its purpose is practical. It provides a balanced framework for dealing with delay and disruption issues, including:

• programmes and records;

• extensions of time;

• contractual notice and procedural requirements;

• contemporaneous assessment of delay events;

• float;

• concurrent delay;

• disruption;

• acceleration;

• global claims;

• prolongation costs; and

• other financial heads of claim.

This breadth is one of its strengths. The SCL Protocol does not look only at delay analysis methodology in isolation. It places delay analysis within the wider context of contract administration, record keeping, entitlement, compensation and dispute avoidance.

That is often how delay issues arise in practice. A delay analysis rarely exists in a vacuum. It is usually connected to notices, programme updates, disputed records, questions of causation, responsibility, concurrency, mitigation and money.

The SCL Protocol is also intended to assist during the life of a project. It expressly discourages a “wait and see” approach to the assessment of delay events and promotes the contemporaneous assessment of extensions of time where practicable. It also deals with analysis that is carried out after the event, including where an EOT application is assessed after completion or significantly after the effect of an Employer Risk Event.

This is an important distinction. The SCL Protocol is concerned not only with retrospective dispute analysis, but also with how delay issues should be managed as the works proceed.

What is AACE Recommended Practice 29R-03?

AACE Recommended Practice 29R-03 has a different emphasis. It is focused on forensic schedule analysis.

It provides a technical framework for understanding and classifying different methods of delay analysis. It also sets out source validation protocols and method implementation protocols. In that sense, it is more analytical and method-driven than the SCL Protocol.

AACE recognises that forensic schedule analysis is both a science and an art. It relies on professional judgement and expert opinion, and usually involves subjective decisions. However, the Recommended Practice seeks to reduce procedural subjectivity by defining terminology, classifying methodologies and setting out recommended procedures for using those techniques.

It is also important to be clear about its timing and technical scope. AACE 29R-03 defines both prospective and retrospective approaches within its taxonomy, but the Recommended Practice itself is focused on forensic schedule analysis. It states that true prospective schedule analysis methods are not discussed, because its focus is on forensic analysis rather than live project administration.

For that reason, AACE 29R-03 is particularly useful when analysing how a retrospective delay analysis has been calculated. It assists with questions such as:

• What type of analysis has actually been performed?

• Was the analysis observational or modelled?

• Was it based on contemporaneous updates?

• Was delay inserted into a programme, or extracted from an as-built model?

• What source data was used?

• Were the baseline, updates and as-built records properly validated?

• How was the critical or controlling path identified?

  
  

These are technical questions, and they matter.

AACE 29R-03 is also primarily a CPM-based forensic schedule analysis document. It is therefore most useful where there are CPM programmes, updates and as-built data capable of technical analysis. That does not mean every simple case requires a full CPM model. AACE itself recognises that there may be simple cases where explicit CPM modelling is not necessary and where mental calculation may be adequate for analysis and presentation. However, its main technical framework is clearly directed towards CPM-based schedule analysis.

The SCL Protocol is somewhat broader in this respect. It recognises the importance of critical path analysis and CPM programming, but also acknowledges that the critical path may sometimes be established through practical analysis of the relevant facts or by analysis of production and/or resource data, rather than by specialist programming software alone.

Are they competing documents?

In my view, they should not be treated as competing documents. They are better understood as complementary references.

The SCL Protocol helps frame the broader questions: What is the contractual purpose of an extension of time? What records should be kept? How should delay events be assessed as the works proceed? How should concurrency, prolongation, disruption and acceleration be approached?

AACE Recommended Practice 29R-03 helps frame the technical analysis: What method has been selected? Is the method appropriate to the data and circumstances? How has the critical path been identified? How have source programmes and as-built data been validated? How transparent and testable is the analysis?

There is also a practical difference in accessibility. At the time of writing, the SCL Protocol is available as a downloadable resource from the Society of Construction Law website. AACE

Recommended Practices are made available through AACE’s own publication and membership arrangements; AACE states that its Recommended Practices are available to AACE members free of charge and available for purchase by non-members.

That practical distinction is worth knowing, but it should not distract from the more important point: the two documents perform different functions.

Both documents also recognise, in different ways, that professional judgement remains essential. Neither document should be treated as a rigid checklist that can be applied mechanically. AACE 29R-03 expressly states that it is not intended to establish a standard of practice or to be a prescriptive document applied without exception. The SCL Protocol similarly states that it is a general guide, not a contract document or a statement of law.

That is an important point. Delay analysis is not simply a matter of choosing a label and producing a chart. The correct approach depends on the contract, the facts, the available records, the quality of the programmes, the timing of the analysis, the purpose of the exercise and the forum in which the opinion may be tested.

Do they agree on delay analysis methodologies?

This question needs a careful answer. They do not present methodologies in exactly the same way, because they are not written for precisely the same purpose.

The SCL Protocol discusses delay analysis methods within the context of assessing extensions of time and delay claims. It also recognises that, where analysis is carried out after completion or significantly after the delay event, a prospective analysis may no longer be appropriate. The second edition moved away from presenting one preferred delay analysis methodology for time-distant analysis, instead recognising that the appropriate methodology depends on the circumstances.

AACE goes much deeper into the technical classification of methods. It classifies forensic schedule analysis methods by reference to timing, basic method, specific method and implementation. Its taxonomy includes observational and modelled approaches, static and dynamic logic, additive and subtractive modelling, single-base and multi-base approaches, and various forms of implementation.

So the better question is not whether the two documents always say precisely the same thing. They do not. The better question is whether they can be read together in a sensible and practical way.

In my view, they can. Both point away from a simplistic “one size fits all” approach. Both recognise that the method of analysis must be appropriate to the circumstances. Both require attention to the quality of records and programmes. Both recognise the importance of causation, critical delay and the surrounding contractual context.

Why the distinction matters in practice

The distinction between the two documents matters because delay disputes often become confused when parties treat references to protocols as a substitute for proper analysis.

It is not enough to say that a method is “SCL compliant” or “AACE compliant”. That phrase may sound reassuring, but it does not answer the real questions.

The real questions are more practical:

• Was the selected methodology appropriate for the contract and the dispute?

• Were the relevant programmes reliable enough to use?

• Were the baseline, updates and as-built records properly considered?

• Was the critical path identified in a transparent way?

• Were the alleged delay events linked to actual delay effects?

• Were competing causes of delay considered?

• Was the analysis proportionate to the value, complexity and available evidence?

• Can the analysis be explained clearly to the tribunal, adjudicator, contract administrator or project team?

These questions matter far more than labels. In my experience, the most persuasive delay analyses are not necessarily the most complicated. They are the ones that use an appropriate method, explain the reasoning clearly, recognise the limitations of the data, and connect the programme analysis to the factual record.

A practical way to read both documents

A useful way to think about the relationship is this:

The SCL Protocol helps answer: What issues need to be managed and assessed?

AACE Recommended Practice 29R-03 helps answer: How can the schedule analysis be technically classified, tested and explained?

For a project team, contract administrator or claims consultant, the SCL Protocol may provide the more accessible starting point. For a delay expert undertaking a forensic analysis, AACE 29R-03 may provide the more detailed technical framework.

However, neither removes the need for careful judgement. A good delay analysis is not created by citing a protocol. It is created by understanding the project, the contract, the programme, the records, the events, the actual progress and the purpose of the analysis.

Where this series goes next

This article has introduced the two documents and the difference in their overall purpose.

In later articles, I will look more closely at specific areas where the SCL Protocol and AACE Recommended Practice are often discussed in practice. These will include:

• delay analysis methodologies;

• contemporaneous versus retrospective analysis;

• float and critical path;

• concurrent delay;

• disruption and productivity loss;

• acceleration and mitigation;

• records and source validation; and

• the role of professional judgement in expert delay analysis.

The aim of the series is not to treat either document as a rigid rulebook. It is to consider how both can assist in producing clearer, better reasoned and more reliable delay analysis.

Ultimately, delay analysis is about more than methodology. It is about explaining what happened, why it happened, whether it mattered to completion, and what conclusions can properly be drawn from the available evidence.

References

Society of Construction Law, Delay and Disruption Protocol, 2nd Edition, February 2017.

AACE International, Recommended Practice No. 29R-03, Forensic Schedule Analysis, 25 April 2011.