Concurrent delay is a very complex issue and different legal jurisdictions have different ways of managing the issue, and there is no clearly defined precedent as to which option is best. Some of the options are:

First cause defines liability This approach argues that liability must rest with the party responsible for the first delay encountered and that subsequent delays occurring during the period of the first delay should not affect liability. This first-intime principle of resolving causation in concurrent delays seems to operate based on the ‘but for’ test. By this test, a party seeks to lay responsibility for project delay on the other party by arguing that the delay would not have occurred but for the latter’s actions or inactions which occurred first. Although such argument is often made, they have received unsympathetic receptions making this an approach that no longer has a wider appeal.

Dominant cause approach This approach argues that the claimant may recover its damages if it can establish that the delay for which the defendant must assume responsibility is the overriding or the ‘dominant’ cause of the loss suffered. Which cause is dominate is a question of fact which is not solved by the mere point of order in time, but is to be decided by applying common sense standards. The problem with this approach is determining a ‘dominant cause’ where two approximately equal causes exist.

The American approach The general view in US case law on concurrent delays in which the employer and the contractor are both responsible for delays to project completion, is that neither party will recover financial recompense unless they can segregate delay associated with each competing cause. However, the contractor will be entitled to a non-compensated EOT to remove his liability for damages for delayed completion during the course of the employer caused delay. The concept of pacing-delays becomes important here; if the contractor can demonstrate its delay was to pace the work within an identified time window caused by the employer’s actions, then the effect of the employer’s delay is segregated from the contractor’s and the contractor is entitled to compensation for the delay. 

The SCL Protocol approach The general principle used by the SCL Protocol is that provided one of the causes of delay in any given concurrency situation affords grounds for extension of time under the contract, then the contractor should be given a time extension notwithstanding any default on his part. The approach supports the prevention principle that states a person asking another to do something cannot insist upon a condition if it is his own fault that the condition has not been fulfilled. Therefore, denying the contractor a time extension in such circumstances could make him liable to the payment of damages even though the project would have been delayed anyway due to employer’s default.

There are more detailed discussions and free downloads on this subject at: https://mosaicprojects.com.au/PMKI-ITC-020.php#Concurrent