In the Society of Construction Law Delay and Disruption Protocol, four retrospective delay analysis techniques are referred to, as follows:
1. As-Planned v As-Built.
2. Impacted As-Planned.
3. Collapsed As-Built.
4. Time Impact Analysis.
A brief analysis of each of these delay analysis techniques is given below.
As-Planned v As-Built
What is the basis of the method?
This method compares the duration of an As-planned activity (or the duration of all As-planned activities) on the original programme with the As-built duration for that same activity (or those same activities) on the As-built programme.
How is the method used to assess Extension of Time entitlement?
The difference in time between the duration on the As-built programme and the duration on the As-planned programme is taken as the period of delay to which a Contractor is entitled to an Extension of Time as a result of an excusable delay event (or delay events) (otherwise known as Employer delay events).
What is needed to make this method work effectively?
The activity or activities need to be clearly on the critical path.
The delay event or events need to be clearly identified.
There should be no other delay events to the activities in question that are non-excusable delay events (otherwise known as Contractor delay events).
What are the strengths of this method?
It is inexpensive to use.
It is simple to use and understand.
What are the weaknesses of this method?
Because no detailed analysis is possible it can only be used on the most simple of construction projects.
It cannot deal with (a) the issue of concurrent or parallel delays, (b) the matter of consequential delay or re-sequencing of works, or © the effects of mitigation and/or acceleration measures.
Impacted As-Planned
What is the basis of the method?
This method adds an identified excusable delay event (or events), either as a separate activity (or activities), or onto the duration of an existing activity (or activities), into the As-planned programme. The duration of the activity is derived (where possible) from the resource allowances on the As-planned programme.
How is the method used to assess Extension of Time entitlement?
The As-planned programme with the delay event (or events) incorporated is then re-run, to show a resultant revised Completion Date on what is then called the Impacted As-planned programme.
The period between the Completion Date shown on the As-planned programme and that shown on the Impacted As-planned programme, is taken as being the period of delay to which a Contractor is entitled to an Extension of Time as a result of an excusable delay event (or events) (otherwise known as Employer delay events).
What is needed to make this method work effectively?
A simple contract or, in the case of more complex projects, delay events that occur only over limited periods or where the As-planned programme has been affected by a limited number of delays only.
An accurate and realistic As-planned programme.
Sufficient details on the As-planned programme to allow a reasonable estimate to be made of the resources necessary (based upon the allowances included in the As-planned programme) to assess the time to be added for the task resulting from the excusable delay event (or events).
What are the strengths of this method?
As-built information is not needed at all.
As the As-planned Impacted programme rarely bears any relationship to what actually happened on site, it can be used to illustrate areas where the Contractor took acceleration measures (or conversely where the Contractor’s actions were deleterious).
What are the weaknesses of this method?
It is a very theoretical method.
It relies heavily on the As-planned programme, and can show misleading results if the As-planned programme is incorrect (either in terms of durations for activities or in respect of logic linking).
As the As-planned Impacted programme rarely bears any relationship to what actually happened on site, it is difficult to use the results to ascertain a Contractor’s actual extension of time entitlement.
If records are available for an As-built programme , then it is unlikely that a tribunal would accept this theoretical method as being a basis for assessing a Contractor’s Extension of Time entitlement.
Collapsed As-Built (also known as ‘As-Built But For’ method)
What is the basis of the method?
This method involves removing from the As-built programme identified excusable delays to show what the Completion Date would have been if those delay events had not occurred.
How is the method used to assess Extension of Time entitlement?
The period between the Completion Date on the As-built programme and the Completion Date on the Collapsed As-built programme, is taken as being the period of delay to which a Contractor is entitled to an Extension of Time as a result of an excusable delay event (or events) (otherwise known as Employer delay events).
What is needed to make this method work?
An accurate As-built programme.
Clear identification of delay events.
What are the strengths of this method?
As this is based upon the As-built programme, there is certainty that the outcome coincides with the events on site.
It is easy to understand.
What are the weaknesses of this method?
The removal of sometimes arbitrarily established delays from the As-built programme can conceal the true effect of the Contractor’s delays, and cannot allow for (a) the issue of concurrent or parallel delays, (b) the matter of the re-sequnecing of the works, or © the effects of mitigation and/or acceleration measures.
The re-creation of a critical path following the removal of delay events may not be the same as the critical path that actually existed at the time of the delay event since the process involves the re-construction of the as-built logic.
In respect of both of the above items, criticisms may be made of the subjective approach that must be used.
Time Impact Analysis
Time impact analysis can be considered under two heads, i.e. Window Analysis (also known as Time Slice analysis) and Snapshot analysis.
As Snapshot Analysis is used primarily only in the event of contemporaneous Extension of Time awards, we will not deal with this method in this Article, and we will only deal with the Window Analysis method.
What is the basis of the method?
Window analysis is based on the analysis of the effects of delay events over the entire length of a project by looking at the events which have affected progress within ‘windows’ of the contract period sequentially.
The duration of each ‘window’ is not pre-determined, but is frequently taken as being one month.
At the end of each ‘window’ the As-planned programme is updated to take account of any delaying inefficiency which is the Contractor’s risk, any necessary logic or duration revisions because of mitigation measures undertaken, together with all excusable and/or compensable events during the period since the last update.
The closing of a window in this way forms an As-built programme at the end of that window which effectively becomes the As-planned programme for the next window in sequence.
How is the method used to assess Extension of Time entitlement?
At the end of each window a projection is made to the Completion Date. At the end of the last window a final revised Completion Date is provided which, when compared to the original As-planned Completion Date, indicates the Extension of Time entitlement of the Contractor.
What is needed to make this method work effectively?
When being used retrospectively, accurate progress information at the time of the windows must be available.
An accurate As-planned programme that reflects all of the activities that should have been included within the original programme.
What are the strengths of this method?
This method is the method recommended within the Society of Construction Law Delay and Disruption Protocol.
In each window there are relatively few activities to be analysed (as compared to the over-all programme) and therefore the delay analysis is easier.
It is the best technique for determining the amount of Extension of Time that the Contractor should have been granted at the time that an excusable risk occurred.
What are the weaknesses of this method?
Accurate progress information at the time of the windows must be available, otherwise the analysis cannot be properly or accurately completed.
The less accurate the programme and progress information available is, the more likely that results will be obtained that are clearly inaccurate, that will require to be amended by manipulating any obvious errors in the original As-planned programme.
Conclusion
There does seem to be some unnecessary confusion regarding the various delay analysis techniques. They are all relatively simple to understand in principle, but (in some cases) are perhaps rather more difficult to operate in practice.
As noted above, each of the techniques has its own strengths and weaknesses, but in reality the delay analysis that is used is often not dictated by the appropriateness of the technique itself but by factors such as, the relevant conditions of contract, the nature of the causative events, the value of the dispute, the time available, the records available, the programme information available, and the programmer’s skill level and familiarity with the project.
Alway Associates