Extensions over a garage for homes in Carshalton
Planning an over-garage extension in Carshalton? We survey the house, work out the planning route, draw the design and build it, so you deal with one team from the first visit to the completion certificate.
- Guide price in CarshaltonFrom £31,000 inc VAT
- PlanningHouseholder application needed
- Build time12–18 weeks on site
- Postcode districtsSM1, SM2, SM3, SM4, SM5
Planning rules that apply in Carshalton
In England any side extension over one storey, including a room built over a side garage, needs a householder planning application. The fee is £548 from 1 April 2026 and councils aim to decide within 8 weeks.
The planning position for a specific Carshalton address depends on its history and any designations, which is why we check it at the first visit.
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).
Extensions in and around Carshalton
Across SM1, SM2, SM3, SM4, SM5, SM6, we can visit, measure and advise. The same team covers Wallington (1 mile), Sutton (2 miles), Mitcham (2 miles), Morden (2 miles), all within easy reach.
For homes towards Surrey, Banstead is around 4 miles away. London's housing is dominated by Victorian and Edwardian terraces, many with a rear outrigger and a side return, and 1930s semis in the outer boroughs. Conservation areas are common, so the planning check comes first.
Is an over-garage extension right for your house?
- Families needing a bedroom without losing garden
- Homes where the landing can connect to the new room
- Detached and link-detached houses with an attached garage
Fitting the new room to the existing landing is the planning puzzle inside the house. We design the connection first, then the roof, so the extension does not end up with awkward steps or a corridor through a bedroom.
How much does an over-garage extension cost in Carshalton?
Prices below are for Carshalton, using the London factor of ×1.3. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Carshalton: £2,340 to £4,420 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Over a single garage 12 m² | £31,000 – £38,500 | £32,500 – £42,500 | £42,000 – £53,500 |
| Over a large single garage 16 m² | £37,000 – £46,000 | £43,500 – £56,500 | £56,000 – £71,000 |
| Over a double garage 24 m² | £56,000 – £69,000 | £65,500 – £84,500 | £84,000 – £106,500 |
Want a range for your exact size? The guide-price tool takes about a minute.
What happens next
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Your questions about an over-garage extension in Carshalton
How long does an over-garage extension take to build in Carshalton?
On site, typically 12 to 18 weeks once approvals are in place. Before that, allow 8–14 weeks design and approvals.
Do I need building regulations approval in Carshalton?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Will my neighbours in Carshalton be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
Can I keep using the garage during the build?
Usually not for parking. The garage roof is removed and the space below is used for access and props for part of the build.
How much does a room over a garage cost?
Our guide range is about £2,340 to £4,420 per m² including VAT. A single-garage room of about 12 m² usually costs £32,500 to £42,500 at standard spec, more if the garage needs rebuilding.
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.