Contractor’s Design

NEC Contractor design is limited to what the Scope says the Contractor is to design. The Contractor submits the particulars for acceptance, doesn't start the related work until they are accepted, and stays liable for the design afterwards.

The rules are at clauses 21 to 23, which have the same numbers in the NEC4 ECC and NEC3. They connect directly to the definition of a Defect, covered in quality and Defects under NEC.

The clauses

Clause	What it does
21.1	The Scope (Works Information in NEC3) says which parts of the works are the Contractor's to design
21.2	Particulars go to the Project Manager for acceptance, and related work waits until the design is accepted
21.3	Design can be submitted in parts, if each part can be assessed fully
22.1	The Client's right to use and copy the design for the stated purposes, and matching rights from subcontractors
23.1	If instructed, the Contractor submits its design for an item of Equipment

How acceptance works

The two stated reasons for rejecting the design are that it doesn't comply with the Scope or doesn't comply with the applicable law. Rejecting it because the Project Manager prefers another solution, where the design meets the Scope, can be a compensation event under 60.1(9).

Reply periods run as for other communications. A failure to reply in time may be a 60.1(6) event. Note how this interacts with the ban on proceeding: if the design hasn't been accepted, the Contractor still shouldn't start the work, and it should raise the delay instead.

Acceptance doesn't shift liability

A Project Manager's acceptance leaves the Contractor's duty to Provide the Works, and its liability for its design, exactly where they were (14.1). So "you accepted it" is not a defence to a design Defect.

A design Defect arises in two ways: the work doesn't follow the Scope, or work the Contractor designed doesn't meet the law or the design that was accepted. If the design as accepted fails to deliver what the Scope requires, that's still the Contractor's problem. And if the Scope itself contains a fault in the design the Client provided, the position flips. That's one of the Client's liabilities.

Changes to the design

The change	Compensation event?
The Project Manager changes the Client's requirements	Yes: 60.1(1)
The Contractor asks to change its own design	No
The Contractor's design changed to meet the Scope the Client provided	No

Keeping the Scope provided by the Client separate from that provided by the Contractor is important here. When the two conflict, you need to know which document is which.

The standard of care: Option X15

Without Option X15, the Contractor has to deliver a design that meets the Scope, whatever level of skill it used, so a design that was competently produced but doesn't achieve the stated result is still a Defect.

With Option X15, the Contractor isn't liable for a Defect arising from its design if it used the level of skill and care professional designers of similar works normally apply. In NEC3 the burden is expressly on the Contractor to prove this. The NEC4 Option also adds record keeping and professional indemnity provisions. A Defect corrected but not the Contractor's liability is a compensation event at X15.2. The X15 guide sets out the detail.

A worked example

A fictional design-and-build retaining wall. The Scope requires the wall to be watertight and meet a stated standard. The Contractor's designer specifies a membrane, and the Project Manager accepts it. Twelve months after Completion, the wall leaks, and the cause turns out to be the membrane choice.

• No X15: this is a Defect, as the work doesn't meet the Scope. The Contractor corrects it at its own cost.
• With X15: the Contractor isn't liable if the designer used the skill and care of a competent professional, and it will need records to show that. If it corrects the Defect anyway, X15.2 gives a compensation event.

A practical checklist

• List each design package and its acceptance date on the programme.
• Make sure the Scope says what particulars are required, and at what level of detail.
• Don't let site start early. Work ahead of acceptance is at risk.
• Pass the same rights to use design down to subcontractors, as 22.1 requires.
• Keep records of design decisions. If X15 applies, they are your defence.

Related guides

• Quality and Defects Under NEC
• Equipment, Plant and Materials
• Keeping a Defects Register
• Quality Management Under NEC4

This guide is general information in our own words, not legal advice. Your contract and its Contract Data always govern. NEC, NEC3 and NEC4 are trade marks of Thomas Telford Ltd; Contract Status is not affiliated with or endorsed by NEC.