Fee guide · London
How much does an architect cost for an extension in London?
It's usually the second question people ask us, right after 'can we do it?'. Fair enough. Nobody likes a mystery bill. So here's how architects charge, what you actually get, and our own numbers, out in the open.
Written by Dor Cohen, RIBA Chartered Architect, ARB Registered
Last updated
How much does an architect cost for a house extension in London?
Architects charge in three ways: a percentage of the build cost, an hourly rate, or a fixed fee per stage. We use fixed fees, so you know the cost of each step before you start. For a 2–3 bed terrace with a ground floor extension, our estimated fee for the survey, 3D model and concept design is £2,400–£4,000 depending on the package. Planning drawings, only if you need them, are from £1,800. Building Control drawings follow once you have permission.
Three ways architects charge
- Percentage of build costCommon for full-service work. Simple, but the fee grows as the build cost grows, and you may not know the final number until the end.
- Hourly rateFair for small, uncertain tasks. Harder to budget for a whole project.
- Fixed fee per stageWhat we do. You see the cost of each stage before agreeing it, and can pause after any stage.
Our estimated fees for a typical North London home
For a 2–3 bed terrace with a single-storey ground floor extension. Your figure depends on your home and scope; these come straight from our current pricing.
| Stage | What you get | Estimated fee |
|---|---|---|
| Essential (Stages 0–2) | 3D scan, existing model and drawings, concept design, remote reviews | £2,400 |
| Complete (Stages 0–2) | Everything in Essential, plus a one-hour site meeting | £3,050 |
| Signature (Stages 0–2) | Our most hands-on concept package, including a site meeting | £4,000 |
| Planning drawings (Stage 3) | Only if needed: drawings, forms and managing the application | from £1,800 |
| Building Control drawings (Stage 4) | Only after permission: technical drawings and engineer coordination | quoted separately |
Fees exclude consultants such as the structural engineer, Building Control body and party wall surveyor. A 15% deposit is due when you sign.
The cheapest drawings often turn out to be the most expensive. Every question left open on paper becomes a variation on site.
What each stage covers
Scan and existing model
A Matterport 3D scan becomes accurate existing drawings in Archicad.
Concept design
Options in 3D, a virtual review, tweaks, then concept drawings you can price against.
Planning, if needed
Application drawings and managing the council for you. Many projects use permitted development instead.
Building Control and engineer
Technical drawings so a builder can price and build without guesswork.
Builders' prices
Clear drawings mean comparable quotes, so you choose on quality, not guesswork.
Questions
Everything you need to know about working with DOR Architects.
For a 2–3 bed terrace with a ground floor extension, our estimated fees for survey, 3D model and concept design are £2,400 (Essential), £3,050 (Complete) and £4,000 (Signature). Planning drawings are from £1,800, only if needed.
A percentage fee rises with the build cost, so it can creep as the project grows. A fixed fee per stage tells you the cost before each step and lets you stop after any stage. We think fixed fees are fairer for homeowners.
No. You agree the concept stages first. Planning and Building Control drawings are separate steps you add only when you need them.
With us: a 3D scan of your home, an accurate existing model and drawings, concept design options and a virtual review. Complete and Signature also include a one-hour site meeting. Package details are on our Pricing page.
No. Structural engineer, Building Control and party wall surveyor fees are separate, paid to those consultants. Our extension cost guide gives typical figures.
Yes. Once you sign the agreement, a 15% deposit secures your place and we start work when it's paid.
Usually, yes. A well-resolved design avoids the expensive changes on site that blow budgets, and good drawings help planning and builders' prices.
Extension architects near you
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