NEC Design Liability

Re: NEC3 Option B Contract

I have a situation where the the contractor raised a shortfall in the works information and subsequently put forward a solution for acceptance.

The contractor at the time liased closely with his supply team and the product manufacturer and issued a design solution comprising some 30 detailed fabrication drawings. The solution was accepted, a CE notified and instructed.

Some 2 years after completion, the building element in question has become defective and requires substantial remediation works to resolve. The contractor contends that he holds no design responsibility for the works even though he provided the design solution that was ultimately constructed. Is the contractor able to absolve himself of the design responsibility in this instance? (The element in question was not originally described in the works information as ‘Contractor Designed’, but in effect became a contractor design proposal.


Your phrase “but in effect” seems to be telling in this case. The phrase illustrates that this is one interpretation of the situation, but in hindsight. However, if the liability for the design was not addressed within the CE and/or a side agreement, then what contractual mechanism does the Employer seek to rely on to transfer the design liability – there seems to be none.

I presume the question is framed in the context that the Contractor’s construction of the revised design was NOT defective, but it is the revised design itself which has proven to be defective.

The Contractor worked in the spirit of mutual trust and cooperation to address a problem at the time. In doing so he submitted a design for consideration which, from your brief description, appeared to have been accepted and adopted by the Employer [PM]. It seems that the alternative design was implemented when the CE was implemented. Therefore, given the brief details here, it seems to me that the liability for the design did not pass to the Contractor. There may be some liability carried by the PM for implementing a design which ultimately proved defective.


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Thanks Neil,

In your view is the design liability a black and white issue of resting with either solely the employer or the contractor regardless of the level of input the contractor had in the design (with advice from other experts).

Yes, given that you said “The element in question was not originally described in the works information as ‘Contractor Designed’” and you have not stated that there was any transfer of obligations or rights in the CE.


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