Carshalton house extensions
From a small utility to a two-storey addition, we take on house extensions throughout Carshalton, starting with a free visit and a planning check.
- Postcode districtsSM1, SM2, SM3, SM4, SM5, SM6
- Price regionLondon (×1.3)
- Planning rulesEngland
- Site visitFree, no obligation
Do extensions in Carshalton need planning permission?
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Popular extension prices in Carshalton
Use these Carshalton guide prices to sense-check a budget; the guide-price tool narrows them to your own size, and the site visit turns them into a written figure.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Single-storey rear extensions | 20 m² | £53,000 – £68,000 |
| Kitchen extensions | 20 m² | £54,500 – £69,000 |
| Orangery extensions | 16 m² | £58,000 – £73,000 |
| Extensions over a garage | 12 m² | £32,500 – £42,500 |
| Double-storey extensions | 32 m² | £74,500 – £98,000 |
| Side return extensions | 11 m² | £34,000 – £43,000 |
Areas we cover around Carshalton
Our survey diary covers Carshalton, including SM1, SM2, SM3, SM4, SM5, SM6. Nearby, we also take on projects in Wallington (1 mile), Sutton (2 miles), Mitcham (2 miles), Morden (2 miles), Croydon (3 miles). For homes towards Surrey, Banstead is around 4 miles away.
Which extension suits a Carshalton home?
In London, space is at a premium and gardens are often short, so side returns, wraparounds and carefully planned rear extensions tend to make the most of every metre.
Start by comparing kitchen extensions, side return extensions and glass box extensions: between them they cover most of the layouts we see requested for houses like these.
Every extension type in Carshalton
- Extensions over a garage · from £31,000
- Timber frame extensions · from £27,000
- Utility and boot room extensions · from £18,000
- Side extensions · from £28,500
- Orangery extensions · from £39,000
- Pitched roof extensions · from £28,500
- Bungalow extensions · from £34,000
- Bedroom extensions · from £33,500
- Kitchen extensions · from £35,000
- Annexe extensions · from £71,500
- Building regulations for extensions · from £1,150
- Glass box extensions · from £39,000
- Wraparound extensions · from £46,500
- Single-storey rear extensions · from £27,000
- Double-storey extensions · from £49,000
- Side return extensions · from £23,000
- Home office extensions · from £20,500
- Flat roof extensions · from £27,000
- Porch extensions · from £5,200
- Extension plans and drawings · from £1,550
- Conservatory replacement extensions · from £26,000
- Planning permission for extensions · from £450
Free site visit
We visit your Carshalton home, measure up, talk through what you want and check the planning position.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Questions about extensions in Carshalton
How much does an extension cost in Carshalton?
Using our London factor (×1.3), a standard-spec single-storey extension of 20 m² is a guide £53,000 to £68,000 including VAT, and a 32 m² two-storey extension £74,500 to £98,000. Your written price follows the survey.
Do you cover all of Carshalton?
Yes, including the surrounding parts of Greater London. Site visits are free and there is no obligation.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for Carshalton, and the guide-price tool gives a range for your own size and finish in about a minute.
How long does an extension take in Carshalton?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Book a free site visit in Carshalton
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.