JCT Design and Build gets mentioned in almost every conversation about procurement route, and almost nobody outside a QS or contracts team could actually explain what it does differently from a standard building contract. Here’s the commercial reality of it, not the legal detail, that’s not something to take from a website article, whoever’s writing it.
The basic shift: one contract, one point of responsibility
Under JCT Design and Build, the contractor takes on responsibility for the design as well as the construction, either by novating the existing design team or building their own. The client ends up with one contract and one point of accountability, rather than a separate contract with the architect and a separate one with the contractor, each pointing at the other when something goes wrong.
What novation actually means in practice
The client’s original design team, the architect in particular, gets novated to the contractor partway through the project, meaning their contractual relationship switches from the client to the contractor, while the individual people and the work they’ve already done generally continue unchanged. Done well, the client barely notices the switch happen. Done badly, it’s the point where a lot of design and build projects start to go wrong, because the architect can feel like their loyalty has shifted whether it has or not.
Payment terms, the commercial detail that actually matters day to day
Interim payments are certified periodically against a valuation of work completed, standard practice across most JCT forms, not unique to D&B. What’s worth understanding specifically here: because the contractor holds design responsibility too, valuations can involve more judgement than a straightforward measure-and-value exercise on a traditional contract, which is exactly why in-house QS involvement matters as much on the payment side of a D&B contract as it does on the cost-planning side.
Risk, and where it actually sits
The headline pitch for D&B is that design risk moves to the contractor. That’s true, but it’s not unlimited, a contractor is generally responsible for the adequacy of the design once it’s in their hands, not for decisions baked into a brief or employer’s requirements before they were ever involved. Where the boundary sits between “client’s original intent” and “contractor’s design responsibility” is exactly the kind of question worth a proper conversation before signing anything, not an assumption either side makes quietly.
The most common misunderstanding
That design and build means the client gives up control of the design entirely. In practice, the employer’s requirements document, agreed before the contract is signed, is what actually defines how much control the client keeps. A thin set of requirements hands more discretion to the contractor. A detailed, well-considered set keeps meaningful control with the client while still getting the single-point-of-accountability benefit the contract is built around.
What this means for you, practically
- If you’re an architect, understand what novation means for your relationship with the client before the switch happens, not after
- If you’re a client, the employer’s requirements document is where your actual control lives, get it right before signing, not after
- If you’re a QS, payment valuation on a D&B contract needs the same rigour as cost planning did earlier in the project, it doesn’t get easier just because one contractor now holds the whole picture