Last edited 18 Aug 2017

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Contractor's design portion

Design drawing cropped.jpg

The contractor’s designed portion (sometimes referred to as 'contractor's design portion' or CDP) is associated with JCT construction contracts. It is an agreement for the contractor to design specific parts of the works.

The contractor may in turn sub-contract this design work to specialist sub-contractors. This should not be confused with design and build contracts where the contractor is appointed to design the whole of the works.

Until 2005, the JCT Standard Building Contract had a contractor’s designed portion supplement for use where the appointed contractor was required to design specific parts of the works.

This provision has now been incorporated into the main contract, but a separate sub-contractor design agreement is available where the main contractor is to design specific parts of the works and a sub-contractor is to design part or all of the sub-contract works.

The JCT Intermediate Building Contract still has a separate contractor’s design agreement, as well as a sub-contractor's design agreement. The JCT Minor Works Contract has a ‘with contractor’s design’ option and a separate sub-contract with sub-contractor’s design.

The client’s requirements for contractor's design will generally be set out in the tender documents as ‘Employer’s Requirements’ in response to which the contractor will submit ‘Contractor’s Proposals’.

Contractor’s design may be used with a Pre-Construction Services Agreement or Pre-Construction Services Agreement (Specialist) to provide early consultancy services to the project before the main construction contract commences.

Often, the portion of design left to the contractor is the detailing work undertaken by specialist manufactures and installers. The main contractor has responsibility for managing the procurement of its specialist sub-contractor’s design in an orderly fashion and to an agreed programme so it can be approved by the client’s design team (who within their conditions of engagement avoid liability for specialist design).

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