I know that normally if Employer causes a delay to the project they could not get the delay damages. That is the reason why time-bar clause is not normally applied to the faults of Employer in many forms of the contract.
However in NEC3 contract, it seems that only clause 61.1 and 61.3 is related to time-bar issue and the CE which arises from the faults of Employer does not waive the need to notify it within the time limit. I doubt that if such event occurs when using NEC3 contract, the Contractor can only avoid the delay damages with it under the law instead of the contract.
The time-bar i think works fine and will stand up to scrutiny in court. If the Contractor is not given access by the Employer, that is a compensation event under 60.1(2). However, the Contractor has eight weeks to notify that the lack of access caused them any problems in terms of time and cost and start the CE process rolling. That is quite generous when the notification only requires a statement as to what the matter is, and what within clause 60.1 makes it a CE. Same principle works for unforeseen ground conditions, weather and indeed 12 of the 19 reasons in 60.1 are the Contractor responsibility to notify.
It stops Contractors leaving everything until the end and then putting forward “claims” that they have never mentioned before and are very subjective to retrospectively assess at that stage. Plus unfair on the Client who had laibilitised costs and may now have difficulty increasing budgets at that late stage to pay for costs they had no idea was coming.
If you remember as far back as NEC2, the timebar used to be only two weeks, but the legal fraternity suggested this was not a legally enforceable timebar, so after discussions was extended to eight weeks, which presumably the same fraternity agreed this WOUlD be legally enforceable.