Under NEC4 ECC, contractor’s design responsibility is one of the most misunderstood areas of the contract and one that regularly causes delay, dispute, and unrecovered cost. In this article, we explain where contractor design responsibility actually comes from, how the design submission and acceptance process works, and what the contract really says when designs are rejected or changed.
Where Contractor Design Responsibility Comes From
Under NEC4, the starting point is always the Scope. Clause 20.1 makes it clear that the Contractor provides the works in accordance with the Scope. If the Scope states that certain parts of the works are to be designed by the Contractor, then the Contractor carries that design responsibility. If it does not say that, then the responsibility remains with the Client. NEC does not assume Contractor design by default. Design responsibility only exists where it is explicitly stated in the Scope.
Contractor’s Design Obligations
Where the Contractor is responsible for design, that responsibility sits alongside the obligation to comply with the Scope.
Even if a design is submitted and accepted, the Contractor remains responsible for ensuring the design complies with the Scope and the contract. Acceptance does not transfer design risk back to the Client. If secondary option X15 is included, it modifies the Contractor’s design liability. So you must always check whether X15 applies and what it says before assuming the standard position.
Design Submission and Acceptance
Designs are dealt with through the submission and acceptance process under Clause 21. Where the Scope requires design submissions, the Contractor submits them to the Project Manager for acceptance. This is a formal contractual process, not an informal review or comment exercise.
Period for Reply
As Clause 21 does not reference a period, the period for reply (as stated in the Contract Data) applies, as per Clause 13.3.
The Project Manager must reply within that period. Late replies matter because they can affect the programme and, in certain circumstances, may lead to a compensation event commonly dealt with under Clause 60.1 (6). There is no automatic deemed acceptance for design submissions just because the Project Manager is late. The Contractor is still held from proceeding with the relevant work until acceptance is actually given. Contractors should always track submission dates and reply deadlines.
Design and the Programme
Clause 31 requires the Contractor to show how the works are planned and performed. Where design submissions affect the sequence or timing of the works, the programme should allow for:
- preparing the design
- submitting it for acceptance
- and the period for reply
If you do not build that logic into your programme, you can end up owning the delay.
When Can a Design Be Rejected?
This is a key NEC principle. The Project Manager can only withhold acceptance for the reasons stated in the contract.
Acceptance is not about preference or alternative solutions. It is about whether the submission complies with the Scope and the contractual requirements.
Requests for Changes or Incorrect Rejection
If the Project Manager replies asking for changes that go beyond the contract grounds for not accepting, treat it carefully.
If the change alters what the Scope requires, it must be issued as a formal instruction under Clause 13. If that instruction changes time or cost, it may give rise to a compensation event under Clause 60.1. Contractors should avoid making design changes without a clear instruction, as this can quickly become unrecoverable cost.
Design, Compliance, and Defects
Clause 11.2 defines a defect as works which is not in accordance with the Scope, or a part of the works designed by the Contractor which is not in accordance with the applicable law or the Contractor’s design which the Project Manager has accepted. So if the Contractor’s design results in works that do not comply with the Scope, that is a defect, even if the design was previously accepted. Acceptance does not remove the Contractor’s obligation to comply with the Scope.
Summary
- Contractor design responsibility only comes from the Scope
- Designs are submitted and accepted under Clause 21
- Acceptance is limited to contractual reasons, not opinion
- Changes must be properly instructed
- And non-compliant design results in defects
