Extensions over a garage in Mitcham: design, approvals and build
Thinking about an over-garage extension for your Mitcham home? Start with a free site visit: we measure up, check what the council will allow and give you honest guide figures on the day.
- Guide price in MitchamFrom £31,000 inc VAT
- PlanningHouseholder application needed
- Build time12–18 weeks on site
- Postcode districtsCR4, SM4, SM5, SW16, SW17
Local to Mitcham
Our survey diary covers Mitcham, including CR4, SM4, SM5, SW16, SW17, SW19. The same team covers Morden (1 mile), Tooting (2 miles), Wimbledon (2 miles), Streatham (2 miles), all within easy reach.
Just over the Surrey border, Ewell is about 5 miles away. 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.
Included in a typical project
- New floor structure, walls and roof
- Opening into the existing first floor
- Design and householder planning application
- Insulation, electrics, heating and finish
- Structural survey of garage walls and foundations
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.
Over-garage extension prices in Mitcham
Prices below are for Mitcham, using the London factor of ×1.3. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Mitcham: £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 |
For a figure based on your own dimensions, use our guide-price tool.
Planning and approvals in Mitcham
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.
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
Building over or within 3 m of a public sewer needs the water company's consent, usually through a build-over agreement, before the foundations go in.
Applications are decided by the local planning authority (your district, borough or unitary council).
How the project works
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
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Work is carried out to the agreed programme, inspected by building control and signed off at the end.
Over-garage extension questions answered
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Mitcham, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Will my neighbours in Mitcham 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.
Do you cover all of Mitcham?
Yes. We cover Mitcham and the surrounding parts of Greater London. Site visits are free and there is no obligation.
Does building over a garage need planning permission?
In England and the rest of the UK, adding a storey over a side garage almost always needs a planning application, because two-storey side extensions are outside permitted development.
Can my garage take the weight of a room on top?
Some can and some cannot. Many garages have a single-skin wall or shallow foundations. Our structural engineer checks this before we give a fixed price.
Book a free site visit in Mitcham
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.