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The analysis of delay on construction projects has developed into something of a dark art, writes Kim Franklin.

The basic concept is simple. Employer and contractor both envisage that the project will be completed within an agreed period. The project does not complete on time and both parties incur unexpected costs. The contract provides various remedies for delay. Liquidated damages may be payable to the employer. The contractor may be entitled to an extension of time, loss and expense.

But in order to take advantage of them, the parties need to demonstrate the causes of the delay and responsibility for them. Three contractual options present themselves: reasons of the contactor's making, that is 'culpable delay';

contractually permissible acts by the employer, such as ordering variations, or breaches of contract, tagged 'acts of prevention'; and reasons beyond the control of both parties, such as bad weather.

In the old days, contractors would support their claim for an extension of time with a bar chart comparing the original contract programme with the as-built position, and highlighting the delaying events with a yellow triangle or similar token. The employer might query whether it was ever possible to build to the programme, wonder whether the yellow triangle actually caused delay at the time on site and might even mention the critical path. But usually a deal was done on some form of empirical basis.

But things have moved on, and now delay analysis is big business. Delay experts have become modern-day necromancers, conjuring network programs of enormous complexity from the bowels of their computers and rival methods, rejoicing in titles such as 'as planned impacted' and 'as built but for' which vie with each other to demonstrate the true causes of delay.

The construction industry's fascination with this topic was demonstrated by the sell-out success of the recent 'Great Delay Analysis Debate' staged by the Society of Construction Law. Delay experts used four different methods in the context of a simple contract completed seven days late.

Alastair Farr of Trett Consulting supported the contractor's claim for a seven-day extension using the 'as planned impacted' method, superimposing delays on the contractor's programme.

Steve Briggs compared the intended programme with the as-built position to demonstrate, on behalf of the employer, that all the delay involved was culpable.

John Hammond, acting as the engineer, used the 'as built but for' approach, starting with the as-built position and 'collapsing' the delaying events, and agreed with the employer.

Keith Pickavance, as the adjudicator, impacted delays onto the critical path as the work progressed and found the contractor was entitled to the halfway house of a three-day extension.

Several points emerged from the proceedings. If you use four different methods to analyse the same set of facts, you come up with three (or more) different answers.

All involve an element of subjectivity. There is no definitive answer.

It is easy to lose sight of the main objective and for the process to become an end in itself. As one experienced expert once confided to me: 'I don't use charts any more, I use photographs.'

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