The sophisticted methods of delay analysis available

In the second of his two articles, Chris Larkin, associate director, Brewer Consulting continues his look at delay analysis, and the importance of choosing the correct technique for any given situation.

COMMENT, Projects

In my first article on delay analysis, I described two simple methods that can be used to assess the delays on a project. The methods I described were as-planned v as-built and impacted as-planned". This second article describes two further more sophisticated methods: as-built but-for and time impact analysis.

In brief, as-built but-for involves removing the effects of delay events from the as-built programme in order to assess how the work would have progressed in the absence of the delays.

First, a dynamic as-built programme is produced using planning software to create a model of the timing and sequence of actual events. The model must precisely replicate how the works were executed using as-built start dates, finish dates and activity durations with appropriate logic links between activities.


The second stage involves identifying the delay events in the as-built programme and apportioning them to the party responsible for them. The delay events are shown in the as-built programme either as activities or constraints. Their impact is modeled by creating logic links between the delay events and subsequent activities.

The third stage involves removing the delays from the as-built programme to produce an as-built but-for programme to show how the works would have been constructed but for the delays. When used in claims for extensions of time, only delays for which the contractor is not responsible are removed. It can then be argued that the extension of time due is the difference between the respective completion dates of the full as-built programme and the as-built but-for programme.

In practice, several iterations are required to ensure that the model represents what would have happened but for the delays. This involves adjusting the level of detail, logic and durations of activities.

As this approach relies upon having an accurate as-built programme, good as-built records are essential. It is also vital that the construction team is consulted in order to gain an understanding of the methods of construction, relationships between activities and practical impact of delays.

This approach has a number of advantages: it is fact-based and less theoretical than other methods; the basic principle is easily understood; and it can be easily presented and explained. It does, however, come with a health warning: care is needed to ensure that the model addresses concurrent culpable delays, re-sequencing, redistribution of resources and acceleration. If such matters are not accounted for then the results will be misleading.

The final method of delay analysis I will describe is called time impact analysis. This method attempts to determine the impact of delay events on the contractor's intentions for the remaining works, taking into account the actual progress at the time the delay event occurred.

The first step is to verify the contractor's planned programme and correct any errors. The second step is to identify delay events and periods. Next, the actual progress of the works at the start of the first delay event is input into the contractor's programme to check whether the completion would have been delayed by the contractor's rate of progress. Activities representing the delay are then added to the program, which is then re-analysed, and any further delay is recorded. It is then argued that the further delay is the contractor's entitlement to an extension of time at the time the delay event occurred. The process is then repeated for each delay event.

Time impact analysis requires a suitable planned program that truly reflects the contractor's intentions for executing the work. This method also requires reliable and consistent progress data at small enough intervals to make the analysis meaningful.

When undertaken properly, this method of analysis addresses the complex issues of concurrent delays, acceleration and resequencing of activities. It is often used by expert witnesses when giving opinions in arbitration or litigation. It is also the method recommended by the Society of Construction Law's Delay and Disruption Protocol.

Due to its complexity, Time Impact Analysis has two significant disadvantages: it can be slow and so expensive to carry out; and can be difficult to communicate the approach and results.

In my view, there is no single method of delay analysis that will suit all situations. The choice of method depends upon the requirements of the contract, nature of the delay events, quality of the planned programme, records to hand, time available, value of the dispute and target audience.

For many of the major projects in the region, speed to market is critical and so any delay can have significant implications. Consequently, the analysis of delays is an important matter and is vital for resolving time-related disputes.

If there were a single method of analysis that yielded only one result from a given set of facts then there would be little doubt as to the party responsible for the delay. Until such a method is found, however, delay analysis will continue to be a subject of much debate.

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