Design and Build London: Stage by Stage
What happens on a design and build project in London, from the first call to the end of the defects period — and which decisions cost money if they slip a stage.
- 4.8★ Google · 17 reviews
- £500 per week if we finish late
- £17m insurance cover · £5m public liability
- 12-month warranty on second-fix fittings · HomePro registered
- £550 survey credited in full
From our Moncrieff Street project — Peckham, SE15
A design and build project runs through 8 recognisable stages, and the build is only one of them. The expensive mistakes are almost never bad workmanship — they are decisions taken one stage later than they should have been, which is a cost you pay without ever seeing it itemised.
People imagine a building project as a construction programme with some paperwork at the front. It is closer to the opposite: a long sequence of decisions, most of them made before anyone arrives, and then a comparatively mechanical period where those decisions get built.
Understanding the order is worth real money, because every decision has a stage where it is cheap and a stage where it is not.
The eight stages, and what each one is for
- Stage 0–1 · Brief: What you want, what you can spend, and whether the building can take it. This is also where the procurement route is decided, and deciding it late throws away most of the benefit of whichever route you choose.
- Stage 2 · Concept: The shape of the thing. Massing, layout, where the light comes from. Cheap to change, and the last point at which changing it is cheap.
- Stage 3 · Developed design: The concept made real enough to submit and to price. Planning goes in around here. Anything you have settled by now is effectively your brief to the contractor, and you own it.
- Stage 4 · Technical design: Construction drawings, specification, building control, party wall where relevant. The contract is signed here, with the particulars filled in — dates, retention, defects period.
- Stage 5 · Construction: The visible part. Strip-out, structure, envelope, first fix, plaster, second fix, finishes. Decisions are still being asked of you, and late answers are the commonest cause of delay.
- Stage 6 · Handover: Practical completion, snagging, certificates, manuals. A retention is normally held from here.
- Stage 7 · Defects period: A fixed period during which the contractor returns to fix what appears. The balance of the retention is released at the end of it.
Where the money actually leaks
Not in the rates. In the timing of decisions.
The kitchen layout is the standard example. It feels like a late, decorative decision and it is structural: it sets drainage, ventilation, the electrical first fix, and frequently a steel. Deciding it at Stage 5 means first fix has already been installed against a different assumption.
Key takeawayThere is no such thing as a small late change to anything that touches services. If a decision moves a drain, a duct or a socket, it is a Stage 3 decision no matter how decorative it feels.
What the build stage is made of
Construction is not one undifferentiated block. Every estimate we produce is broken into the same twelve stages, from preliminaries to completion, with a quantity, a unit and a rate on each line — which is what makes it possible to see where money is going rather than watch a single figure move.
That granularity matters to you for one practical reason: it tells you what is happening this week and what has to be decided before next week. A stage-by-stage breakdown is a decision calendar as much as a price.
What is expected of you
- 01Settle the route before the design runs away.. Design and build, traditional, or novated. Choosing after a full design exists wastes the advantage of whichever you pick.
- 02Answer decisions when they are asked, not when convenient.. Most delays blamed on contractors are decision delays. A trade cannot start until something has been chosen.
- 03Approve variations in writing, before the work.. Nothing should be charged without your written approval, and the price should be agreed before the work happens rather than valued afterwards.
- 04Read the contract particulars, not just the sum.. Completion date, extension of time, retention, defects period. This is the part people skim and then argue about.
- 05Look at what is reported.. Reports are only worth the reading. If what you are shown does not match what you expected, say so that week, not at handover.
Where we fit
We run this as one contract with the design handled by our design and build service, so the decision calendar and the build programme belong to the same people. How we run a project sets out the reporting in detail, and the two companion pieces cover the choice itself — who carries the gap and what you will actually sign.
For a range before any of this starts, the estimator prices off the same rate card we contract from, and narrows as you answer more about the job.
Straight answers
The home you actually want, finished on the date in the contract — and you watch every day of it happen from your phone.
You answer 3 questions. We do the drawings, planning, party wall, trades and snagging.
- 10% to mobilise, then weekly against work already done — with 5% held past handover: 2.5% released at practical completion and 2.5% at the end of the 12-month defects period
- £550 survey fee credited in full against your contract
- Every variation priced and signed before a penny is spent
No email needed to see your range. Quotes hold for 21 days, then materials re-price.
We are not the cheapest. If price is the only factor, we may not be the right fit — and that is fine.
Keep reading
- JCT Design and Build: What You Will SignJCT Design and Build is a real contract with a real design-liability clause — and almost certainly not the one your London extension will be built under.
- Design and Build vs Traditional: Who Carries the GapThe 2 routes differ in one thing: who pays when the drawings and the building disagree. What each costs you, and why neither removes variations.
- What the Skip Costs: Strip-Out, Landfill Tax and the Waste You Design InLandfill tax is £130.75 a tonne from April 2026. A fit-out that sheds 3.5 tonnes pays £463 in tax alone before the skip, the lorry or the labour.
- Build It So It Comes Apart: Specifying Partitions That Survive the Next TenantA 6-metre plasterboard screen sends 571 kg of gypsum to the skip every time it is rebuilt. A demountable one sends none — but only if the drawings allow it.