House extension drawings
London-wide, £1,880 all-in. Design drawings, your planning or prior approval application prepared and submitted, building regulations drawings, structural calculations and a full measured survey. No hidden fees.
Start with the free checkTrained on 20 million+ UK planning applications. See the full price list or the sister loft conversion drawings service.
All-in design and planning package
£1,880
One fixed price for a house extension of any of the types below. Design to structural calculations, handled by one team.
Included
- Design drawings for your extension
- Planning or permitted development / prior approval application, prepared and submitted for you
- Building regulations drawings
- Structural engineer calculations
- Party wall notices for your neighbours, where needed
- Full measured survey of your property, completed at the building regs stage
- Unlimited design revisions
- Free amendments if the council requests changes
- Free resubmission if your application is refused
Not included
- Council application fee, paid direct to your council - £548 for a householder planning application, £274 for a lawful development certificate, or £249 for a larger home extension prior approval
- Building control inspection fees when you build
- Party wall surveyor, only if a neighbour formally dissents
Standard extensions only. Basements, new builds, listed buildings and change of use are quoted individually, typically from £2,495.
Pay in two stages
The total is always £1,880. You pay as the work happens, not up front.
| Stage | What it covers | You pay |
|---|---|---|
| Stage 1 | Design drawings and your planning or prior approval application, submitted to the council First drawings within 2 weeks of instruction - designed from planning records, property data and your photos, so there is no survey to wait for before we reach submission. | £1,180 |
| Stage 2 | Measured survey, building regulations drawings and structural calculations, ready for builders to quote Starts once your approval is in. We survey your property before producing the technical drawings. | £700 |
Only need planning drawings? Stop after Stage 1 - you pay £1,180 and nothing more.
Price match guarantee
Found a genuine written quote for less? If it covers the same all-in scope - design drawings, planning application, building regulations drawings, structural calculations and survey - we will match it.
Like-for-like scope only, standard residential projects only, at our discretion.
Every extension type
The £1,880 package covers all of these. Whether permitted development, prior approval or full planning applies depends on your property - flats and maisonettes have no permitted development rights, and conservation areas commonly restrict or remove them entirely.
Rear extension
The most common extension in London. Under standard permitted development, a single-storey rear extension can go back 3m on a terraced or semi-detached house, or 4m on a detached house, without planning permission. The larger home extension prior approval route can extend that to 6m on a semi or terrace and 8m on a detached house - it is not available in a conservation area. Usually the most straightforward route to extra space.
Full guide to London extension costsSide return extension
Fills the gap down the side of a terraced or semi-detached house, most often to open up the kitchen. Single-storey side extensions can fall under permitted development up to half the width of the original house, but conservation areas commonly remove this right, so a full householder planning application is often needed instead.
Full guide to side return extensionsWrap-around extension
Combines a rear and side return extension into one design, usually the most extensive - and most expensive - of the ground-floor options. Because it takes the full width and depth together, most wrap-arounds exceed permitted development limits and need a full householder planning application.
Compare extension optionsTwo-storey extension
Adds space on two floors rather than one. Under permitted development, a two-storey rear extension is limited to 3m in depth and must sit at least 7m from the rear boundary, with height and roof pitch matching the existing house. Go beyond those limits and it needs full planning permission.
Full guide for detached housesKitchen extension
Rarely a separate class of its own - almost always built as a rear or side return extension, with the planning route depending on which shape and size you choose. The layout decision usually matters more for cost than the fact that it happens to house a kitchen.
Full guide to kitchen extension costsHow it works
Four steps from first check to a package builders can price.
1
Free planning check
Before you spend anything, our free check tells you whether your extension needs planning permission, whether it qualifies for permitted development or prior approval, and flags any constraints on your property such as a conservation area or an Article 4 direction.
2
Design and submission
First drawings within 2 weeks of instruction, prepared from planning records, property data and your photos - no survey appointment to wait for. We refine the design with you, then submit your application and handle the council from there.
3
Measured survey
Once your approval is in, we complete a full measured survey of your property - the precision base the technical drawings are built from.
4
Building regs package
We produce building regulations drawings and structural engineer calculations so builders can quote accurately and get started.
Converting the loft instead, or as well?
The same £1,880 all-in package and process applies to loft conversions - design drawings, planning or permitted development application, building regulations, structural calculations and survey.
Loft conversion drawingsFrequently asked questions
Click each question to read the answer.
Do I need planning permission for a house extension in London?
It depends on the size, position and your property. Many single-storey rear and side extensions fall under permitted development and need no planning application at all, though you may still want a lawful development certificate to confirm it in writing. Flats and maisonettes have no permitted development rights and always need full planning permission for an extension. Conservation areas and Article 4 directions commonly remove permitted development rights too, and the larger home extension prior approval route is not available inside a conservation area. Use Mayfair Studio's free planning permission check at mayfairstudio.co.uk/planning-permission-check for an instant answer on your specific property before you spend anything.
How much do house extension drawings cost?
Mayfair Studio charges one fixed price of £1,880 for a standard extension. That covers design drawings, your planning or permitted development / prior approval application prepared and submitted, building regulations drawings, structural engineer calculations, party wall notices where needed, and a full measured survey. Traditional architects typically charge separately for each of these stages, with structural calculations often billed on top.
What exactly is included in the £1,880?
Design drawings, your planning or permitted development / prior approval application prepared and submitted, building regulations drawings, structural engineer calculations, party wall notices for your neighbours where needed, and a full measured survey completed at the building regs stage. Also included: unlimited design revisions, free amendments if the council asks for changes, and free resubmission if your application is refused. Not included: your council application fee (paid direct - £548 for a householder planning application, £274 for a lawful development certificate, or £249 for a larger home extension prior approval), building control inspection fees, and a party wall surveyor in the rare case a neighbour formally dissents.
Can I pay in stages?
Yes. Stage 1 is £1,180 and takes you from first drawings through design to a submitted planning or prior approval application. Stage 2 is £700 for the measured survey, building regulations drawings and structural calculations once your approval is in. The total is always £1,880 - no extras between stages, and if you only need planning drawings you can stop after Stage 1 at £1,180.
Do you offer a price match guarantee?
Yes. If you have a genuine written quote from another UK practice for the same all-in scope - design drawings, planning application, building regulations drawings, structural calculations and survey - on a standard residential extension, we will match it. Like-for-like scope only, standard projects only, at our discretion.
How long does the process take from instruction to submission?
First drawings arrive within 2 weeks of instruction, because we design from planning records, property data and your photos rather than waiting for a survey appointment. Your application is typically submitted within about 3 weeks of instruction. The council then usually takes 8 weeks to decide on a householder application. The measured survey and building regs package follow once approval is granted.