How the two arrangements work
With traditional procurement, the client appoints consultants to develop the design and a contractor to build it. JCT describes completing the design before tender as an important basis for comparing prices and controlling subsequent change. Construction-stage services need to be included in the consultants' appointments: buying drawings is not automatically the same as appointing someone to administer the building contract. [2]
In design & build, the contractor may use its own designers or external consultants. The client's requirements establish what must be delivered, while the contractor develops the agreed design responsibility. Design & build can therefore include substantial design work by the client before the construction contract is signed. [1]
Compare the actual services
Prepare a responsibility schedule for both offers. As a practical comparison, ask each team to identify who will:
- complete the drawings, engineering and specifications;
- coordinate specialist designs and resolve inconsistencies;
- apply for approvals and answer technical queries;
- assess payments, approve changes and inspect workmanship;
- assemble completion documents and manage reported defects.
This turns a procurement label into named appointments and deliverables. JCT's contract descriptions distinguish the employer's agent in design & build from the separate design-and-construction appointments used in traditional procurement. [3] [2]
Control over the finished design
A requirement such as “provide an extension” leaves more decisions unresolved than a coordinated package specifying layout, finishes and performance. Before signing, identify what is fixed, what remains the contractor's choice and which substitutions need approval. JCT highlights the importance of adequate employer's requirements in design & build. [1]
An independent adviser can be retained under either route. Specify the adviser’s authority rather than assuming that attending a meeting gives them power to instruct the contractor or certify a payment. The contract and professional appointment need to fit together. [3] [4]
Do not decide on the label alone
Request comparable scopes, price assumptions and programmes. In your comparison, ask whether each apparent saving represents a lower price for the same work or a responsibility omitted from that offer. Beside every unresolved choice, record who will decide, who will obtain a price and who must approve it.
Neither route removes building-regulations duties. England's dutyholder guidance requires appropriate competence and coordination; the relevant roles must be addressed regardless of the commercial arrangement chosen. [5]