Rather than looking at the causes of critical delay and then ascertaining the potential effects on the programme activities and completion date, the approach is to understand the actual effects and then look for the likely causes.
When starting a retrospective analysis, the view is from the end of the project looking back to the start. It entails gathering all the programme related data and correspondence to understand how the project progressed. The data can include progressed programmes, progress reports, correspondence, site diary entries, photographs, labour returns, material deliveries etc. In short it is anything that helps to build up an accurate picture of how the works progressed.
The data gathered can be used to produce an as-built programme and this can be compared to the original intent. This is useful when identifying where divergences have occurred from the initial programme of works. The as-built programme represents the effects of all causes and there can be many different categories of cause. These include both compensable and non-compensable events. This means events were the contractor may be entitled to additional time and/or money and those events that are his responsibility.
It can be difficult to determine accurately the critical delay due to each event, so it can be useful to divide the overall project programme into several windows. These windows may coincide with the date of progress reports or at significant points in the project. Dividing the programme up into these bite size chunks helps with the analysis of the events.
Prospective analysis forecasts the impact of an event upon the remaining works and completion date. This type of analysis is most appropriate at the time of an event and provides visibility about the potential impact at that time.
There are many different delay analysis techniques and the Society of Construction Law provides some useful guidance in the second edition of the delay and disruption protocol. No delay analysis technique is perfect but some are more appropriate given the available data and when the analysis is carried out. The choice of technique is reduced if the quality of the programme information and supporting documents is poor. Therefore, it is important to have in place protocols for the provision of good programme and progress information at the start of a project as the provision of this information once a dispute has arisen may be very difficult.
