By Rob Allison, founder of Thames Design & Build
If you’re planning an extension or renovation in Surrey, you’ll come across two ways of doing it. You can appoint an architect to design the project, then find a contractor to build it. Or you can use a design and build company, where the same business does both under one contract. This design and build vs architect Surrey decision is the first one that shapes everything else about your project.
Most people starting this process haven’t come across the distinction before — they just know they want an extension. So here’s a straight comparison of design and build vs architect and contractor in Surrey, including where each route falls short.
The traditional route: architect, then contractor
This is the model most people default to, because it’s what’s been done for decades. You appoint an architect to design your extension, take it through planning, and produce the drawings. Once those are finished, you go out to tender — getting quotes from two or three contractors to build what’s been designed.
The model has a structural weakness: the architect designs to what’s possible on paper, and nobody prices it properly until the drawings are finished and out to tender.
We saw this play out recently with a client who’d already had their architect draw up a scheme — a two-storey side extension, a single-storey rear extension, and a full house refurbishment. When we priced it, the whole scheme came in well outside their budget. They had to go back to the architect, have the drawings redone to drop the single-storey rear extension, and only then could we build the rest within what they could actually spend. That cost them weeks, and it meant finding out — quite late in the process — that they couldn’t have everything they’d been picturing.
That’s not the architect’s fault, or the contractor’s. It’s what happens when design and cost are two separate conversations that only meet once the drawings are already finished.
Tendering itself adds time too — typically four to eight weeks once drawings are complete, on top of whatever design and planning took.
Design and build vs architect Surrey: one team, one contract
Under a design and build model, the same company designs and constructs the project. At Thames Design & Build, our RIBA-chartered architects develop the design alongside our estimating and construction team from the start, rather than handing over finished drawings and stepping back.
That gives you four things the traditional route can’t:
One point of responsibility, start to end. If something goes wrong, there’s no architect-versus-builder argument with you stuck in the middle trying to work out whose fault it was. It’s on us, and we sort it.
Cost advice that’s live throughout design, not bolted on at the end. Mikael, our estimator, gives budget cost advice while the design is still being worked out — not a full price, but enough to know whether the scheme’s heading somewhere affordable, well before the drawings are finished and a rear extension has to be cut to fit the budget. That’s precisely the scenario above, and it’s the reason we do it this way: cost and design need to be the same conversation, not two conversations that collide at the worst possible moment.
One team, working together properly. Design and construction sit under one roof, so issues get resolved by people talking to each other directly, not through emails between two separate businesses with different incentives.
A seamless handover from design into build. There’s no gap where a project sits between an architect who’s finished their part and a contractor who hasn’t started theirs.
What “one point of responsibility” actually means
One team means we can’t point elsewhere when something on our side goes wrong. That happened to us, roughly once a year. On one project, a wall was marked as being demolished on the existing drawings, but wasn’t shown as needing to be rebuilt on the proposed ones — an oversight in the drawings themselves. Our site team knocked it down before anyone caught the mismatch. Because it was our own design, there was no separate architect to point to, and no one else to blame. We fixed it and absorbed the cost — because that’s what one point of responsibility actually means when it’s your own team that’s slipped up, not just when it’s convenient.
That’s the real difference between design and build and the traditional route: when something goes wrong, you’re not left waiting while an architect and a contractor argue over whose fault it is and who’s paying for it. It’s on us, and we sort it — every time, not just when it suits us.
Questions worth asking either way
Whichever route you’re considering, these are worth asking upfront:
- Who is actually responsible if there’s a problem on site that traces back to the design?
- How much will the price move between first estimate and signed contract, and why?
- Who’s your single point of contact, and what happens if the architect and contractor disagree?
- How long from initial enquiry to a fixed price you can actually rely on?
If you can’t get a straight answer to any of those, that’s worth noticing — whichever model you’re comparing.
Where this leaves you
When it comes to design and build vs architect Surrey decisions, most of the extensions and renovations we build in Thames Ditton, Esher, Cobham and the surrounding area are people who wanted one team, one contract, and cost advice they could trust from the first meeting — not a nasty surprise after the drawings were already done.
If you’re not sure how design and build would work for your project, that’s exactly what an initial site visit is for. Get in touch and we’ll walk you through it.