Delay analysis with CPM

Critical Path Method (CPM) is a method based on subtracting delays from the as-built programme and in order to determines the earliest date that the contractor could have completed.

1. First identify as-built dates for the construction activities in sufficient detail for identification of delays to be made.  

2.These as-built start and finish dates can then be stored in the programme software which allows static bars to be created which reflect the as-built programme but without logic.  

3,The next task is to identify the actual logic relationships to create a logically linked network such that each activity has scheduled start and finish dates that match the as-built durations already identified. 

4, Delays are then added to the programme as separate activities by identifying those parts of the as-built durations that are periods of delay.  This can be seen in the first part of the programme above.  It may be possible and appropriate to identify contractor caused delay as well as Employer’s delay (EOT events) in order to analyse potential concurrency as in the example above.  

5. The delays are then collapsed out of the as-built programme, and there are various approaches to determining the effect of each event. In the example above it can be seen that there is potentially a concurrency situation.  The as-built critical path indicates that the delay to activity 2 (for which the contractor is responsible) is driving the completion date, but say that this was the work to remedy a defect discovered upon completion of the work to activity 2 on 1 February leading to the subsequent completion of the activity on 7 February. 

 Further, say the delay to activity 4 for which the employer was responsible was a variation to work that had been otherwise completed on 25 January leading to procurement of additional materials and completion of the work on 6 February.  It could then be argued that the employer’s delay came first and at that time event 2 was on programme.  

The effect of collapsing the employer and contractor delays out in this situation would result in the conclusion that in fact at the time of the start of the employer delay to activity 4, this delay was critical thus causing a delay to completion of 3 days for which the Contractor should receive an extension of time.  

The subsequent contractor’s default caused a further delay to completion of 1 day.  In order to show this, both delays have been collapsed out to determine the collapsed as-built completion date and the employer event has been added back to demonstrate the effect on the completion date.

The tedious part about this method is to get the as built logic correct. it's better get the record straight upfront rather then penalised by client for the Project delays.