Design and build is a generic term describing a procurement route in which the main contractor is appointed to design and construct the works, as opposed to a traditional contract, where the client appoints consultants to design the development and then a contractor is appointed to construct the works.

Design and build can appeal to clients as it gives a single point of responsibility for delivering the entire project. Some clients however consider it is only appropriate for simple projects, where design quality is not the main consideration.

The contractor can either be appointed to carry out all of the design work, or if the client wishes to have greater influence over the design, a concept design and outline (or performance) specification can be prepared by a consultants employed by the client, and then the contractor is appointed to complete the design and carry out the construction.

The contractor may use their own in-house designers to design the building, or they can appoint consultant designers, or the client’s designers can be employed by the contractor to complete the design (either by novation or consultant switch).

If the contractor is appointed at the outset of the project (so that they can contribute to the development of the design from the beginning), they may be appointed through a two-stage process. In the first stage, the contractor is selected on the basis of a fee, preliminaries, overheads and profit. They then work with the design team (who may be employed either by the contractor or by the client at this stage) to develop the design, on the basis of which a fixed price is negotiated for the second stage; construction, when the design team may be novated to the contractor if the contractor does not already employ them.

Design and build is one of the three procurement routes favoured by the government for publicly-funded projects, as it allows a fully integrated team to work together on the project from the beginning.

Design and build contracts can be awarded on a fixed-price, lump-sum basis, but price certainty is then dependent on not making any subsequent changes as these could prove to be expensive (as prices charged by the contractor for those changes will not be subject to competition). It is very important therefore that the client gives a great deal of consideration to the preparation of employer’s requirements, and if they have not appointed their own design team, they may wish to appoint independent client advisers to help them do this. Similarly if any designers appointed by the client are novated or switched to work for the contractor, the client may then wish to appoint independent client advisers to review contractor’s design proposals, administer the contract and monitor works on site.

Design and build contracts include:

  • Joint Contracts Tribunal (JCT) DB 05 (also JCT Major project contract and JCT Constructing excellence contract).
  • The Association of Consultant Architects ACA/2.
  • Government Contracts GC/Works 1 (single stage or two stage) NB GC Works contracts are no longer being updated by the government.
  • Institution of Civil Engineers (ICE) Design and Construct (this has now been withdrawn in favour of NEC3).
  • The New Engineering Contract (NEC) Engineering and Construction Contract NEC3.


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