Design and Build

A logistics company needs a new depot but does not want to coordinate separate full-design and construction contracts, so it sets functional requirements and appoints one design-and-build contractor, who is then responsible for completing the design and delivering the works as the agreement specifies. Under a traditional model, by contrast, the client generally engages designers to develop a fuller design before tendering construction.

Employer or client requirements should be written clearly, because capacity, layout, safety, quality, planning and performance needs should be testable and a vague brief can produce a compliant-looking building that does not work for operations. A contractor may provide proposals showing how it will meet those requirements, so check the relationship between requirements, proposals and the signed contract, since unresolved inconsistencies can become disputes over which document controls.

The JCT Design and Build Contract 2024 describes a contractor responsible for completing design and carrying out the work, with detailed employer requirements, and uses a lump-sum price with interim stage or periodic payments. That describes this UK form, not every contract called design and build.

One main contract can simplify the client's route for design-and-construction claims, though it does not remove interfaces with regulators, landowners, utilities or separate client suppliers. The client may hire an adviser to prepare requirements and review the contractor's submissions, and that adviser can support decisions while the contractor retains the contractual design duties it accepted.

Design and construction phases may overlap, so early enabling works can begin while later details are developed if permits, information and sequencing allow it, which can reduce a programme in a particular project but guarantees no fixed number of months saved. Late changes can be costly, as a client who alters warehouse height after steel fabrication may face price and time consequences, so set approval rules, variation procedures and a decision log before work accelerates.

Cost certainty depends on the scope and contract terms: a lump sum for a stable brief may help forecast, but provisional items, instructed changes and unforeseen conditions can alter the amount, so do not call it an all-risk fixed price without reading the agreement. RICS procurement guidance discusses route selection in terms of objectives, client resources, cost, time and the ability to make changes, applies to the UK and Crown Dependencies and says regional legal requirements take precedence, and it helps ask questions rather than prescribe one route universally.

During tender, compare quality as well as price, and ask bidders to identify assumptions and exceptions so offers can be compared fairly. Review contractor design at agreed stages, with approval or comment procedures clear about whether client review changes responsibility, since a rubber-stamp process is risky while endless redesign undermines the route's speed.

Check professional indemnity and other relevant insurance against actual design risks and contract promises, because insurance terms, exclusions and limits matter and a policy is not a guarantee that every defect will be paid for, so specialist advice may be needed. Plan handover requirements from the beginning, since commissioning results, operation manuals, as-built information and training help the client use the completed building, and a project is not operationally ready merely because major construction looks finished.

An illustrative programme comparison is the planned duration of a traditional route minus that of a design-and-build option: twenty-four months versus nineteen suggests five months on paper, so validate assumptions, procurement lead times and risk before treating the difference as achievable. For owners, design and build may suit a clear, stable brief and a desire for integrated delivery, but it may be less comfortable when the client expects to control every design detail or make frequent changes, so select the route for the project and then document the roles and decision points.