Delay analysis in construction projects

Melanie Blake and David Owens examine methods of delay analysis in construction projects.

Introduction

Delays to works are a common issue in construction projects. The exact cause(s)  of any delay are not always easy to pinpoint, due to the complex and intricate nature of construction projects. Independent delay experts are often needed to analyse delays (thus helping to establish liability) by doing the following:

• Determining the critical path. The Society of Construction Law (SCL) protocol defines the critical path as being, “…the longest sequence of activities through a project network from start to finish, the sum of whose durations determines the overall project duration”;
• Assessing the extent of the delays; and
• Assessing the causes of the delays.

Types of delay analysis

Delay analysis methodologies can be either “prospective” or “retrospective”. Prospective methodologies involve assessing delays as at the time the events in question occurred (i.e. they look at the cause of the delay first, and then the effect of the delay). Retrospective methodologies consider events that have already happened, in order to establish whether the events in question actually caused delay to completion when the progress of the work as a whole is considered (i.e. they look at the effect of the delay first and then the cause).

Retrospective methodologies are more commonly used due, in part, to the fact that  delay(s) have already happened by the time an expert is instructed and there is likely a dispute between the parties as to the cause of the delay.

The six main types of delay analysis are:

Prospective:

1. Impacted As Planned
2. Time Impact Analysis

Retrospective:

3. As Planned v As Built Windows
4. Longest Path
5. Time Slice Windows
6. Collapsed As Built

We explore in more detail below the types of retrospective delay analysis.

1) As Planned v As Built Windows

This form of delay analysis compares the as-built programme to the as-planned programme. In other words, it compares events that actually took place during a project’s execution to how things were planned to take place at the start of the project. It is therefore less reliant on programming software than other methods of delay analysis and works by tracking and calculating the change in the critical path.

The as-planned and as-built programme are broken down into time slice windows. Splitting complex programmes into windows in this way helps delay experts to analyse the delays as they look at each window in turn over discrete periods of time.

Because this method requires the as-built programme, it is heavily reliant on the availability of as-built records and contemporaneous evidence such as photographs, correspondence and reports. Although this makes this method of delay analysis resource-intense and expensive, it means that it is heavily rooted in fact (unlike some other delay methods). It identifies the actual delay (unlike prospective analysis which largely calculates hypothetical delays). This therefore makes it a popular method of delay analysis in terms of being able to accurately evidence the causes of delay.

2) Longest Path

This is another retrospective method of delay analysis and is similar to As Planned v As Built Windows, except the project is looked at as a whole rather than being broken down into time slices. It works by tracing the longest continuous critical path back from the actual completion date to determine the actual critical path. It therefore only uses the as-built programme to determine a single critical path, unlike As Planned v As Built Windows which looks at both the as-built and as-planned programme to compare changes to the critical path. The Longest Path method therefore has limited capacity to recognise and allow for switches in the critical path during the course of the project, and for this reason it is rarely used.

3) Time slice windows

This retrospective method of delay analysis is an observation-based methodology. Delay events are not added into the programme. Instead, the as-planned and as-built programmes are reviewed and compared with each other. The total project duration is divided into smaller periods (known as “windows”) and each window is reviewed to analyse the change in the critical path within that window.

Although similar to As Planned v As Built Windows, the time slice windows analysis relies on the contemporaneous programmes provided by the contractor. It is therefore based on projected progress during the dates when updates to the programme were shared by the contractor. This allows for the observation of delays in real time and a deeper understanding of the delays as they unfold. It is in this sense a dynamic method of delay analysis (despite being retrospective) which makes it particularly useful as it considers the evolving nature of project activities. It is a comparatively expensive method of delay analysis and requires complete project records and reliable as-planned and as-built programmes. It is also one of the more time-consuming methods to perform.

4) Collapsed as-built

This retrospective method is also known as the “subtractive” method of delay analysis, as it involves the removal of delay events (i.e. “collapsing” the programme) in order to generate a theoretical programme “but for” those delay events. It works by plotting out the as-built programme (using project records etc), inserting known delay events, and then removing them to give a theoretical completion date “but for” the delays arising. This method of delay analysis is only used when there is no as-planned programme in existence. It is time-consuming, resource intense and its reliability is questionable (due to the subjectivity of how logic links are added). It is very rarely used.

What courts and tribunals think of the various methods

In Skanska Construction UK Ltd v Egger (Barony) Ltd[1], Judge Wilcox made it clear that:

“the reliability of [the expert’s] sophisticated impact analysis is only as good as the data put in”.

The courts are more likely to be satisfied with a delay analysis when the method in question properly uses the facts available to give rise to an answer rather than the risk of it being hypothetical in nature.

The courts have also acknowledged that there is no requirement to strictly adhere to the 6 methods of delay analysis set out in the SCL protocol. In Thomas Barnes & Sons Plc (In Administration) v Blackburn with Darwen Borough Council[2], HHJ Stephen Davies stated that it was not appropriate to require a strict adherence to the SCL protocol, and quoted from paragraph 11.2 of the protocol that:

“irrespective of which method of delay analysis is deployed, there is an overriding objective of ensuring that the conclusions derived from that analysis are sound from a common sense perspective.”

HHJ Stephen Davies did however note that:

“…if an expert selects a method which is manifestly inappropriate for the particular case or deviates materially from the method which he has said he is following, without providing any, or any proper, explanation, that can be a material consideration in deciding how much weight to place on the opinions expressed by the expert.”

The courts therefore acknowledge that the six methods set out in the SCL protocol are for guidance only, and that they will not necessarily take an adverse view purely because an expert has adopted a different method. The important thing is that the method chosen is justifiably appropriate for the circumstances of the case, therefore leading to a conclusion that is “sound from a common sense perspective.”

Conclusion

Delay claims are one of the most common sources of disputes in the construction industry. The suitability of each particular method of delay analysis is ultimately dependent on a variety of factors, including:

• the length and type of project;
• the availability of contemporaneous records;
• the availability of as-planned and as-built data;
• the availability of project programmes and whether they were updated during the course of the project; and
• when during the project a delay expert is instructed (i.e. prospective vs retrospective).

Regardless of the method used, delay analysis is widely recognised as not being an exact science, and the outcome of a delay analysis exercise can be easily manipulated by a variety of factors.

If a delay expert is to be instructed it is wise to ensure that:

(1) the expert in question has the relevant qualifications and experience (delay analysis is, after all, an extremely complex task);

(2) the expert is able to pick a suitable method of delay analysis, preferably one which is able to give the most factual (rather than hypothetical) conclusion possible; and

(3) the expert is able to justify this chosen method to a court or adjudicator. It is important to remember that the most complex methods are not always the most appropriate, and the courts far prefer to see a delay analysis which uses the facts of the case.

Melanie Blake is an Associate and David Owens is a Partner at Sharpe Pritchard LLP.

[1] [2004] EWHC 1748

[2] [2022] EWHC 2598 (TCC)

This article is for general awareness only and does not constitute legal or professional advice. The law may have changed since this page was first published. If you would like further advice and assistance in relation to any issue raised in this article, please contact us by telephone or email This email address is being protected from spambots. You need JavaScript enabled to view it.