Extensions over a garage in Coulsdon
For an extension over a garage in Coulsdon, the first questions are always the same: how big, which approvals, and what it will cost. This page answers all three for Greater London.
Quick reference for homeowners in Coulsdon.
- Postcode districts
- CR5
- County / area
- Greater London, England
- Price region
- London
- Guide price
- £38,000–£55,000 (£2,100–£3,060 per m²)
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Nearest towns
- Purley (1.7 miles), Kenley (1.8 miles), Banstead (2.9 miles)
- First visit
- Free, no obligation
About an extension over a garage
An extension over a garage suits you if you have an attached single garage beside the house and need an extra bedroom or a larger main bedroom with an en-suite. You get an inspection of the garage structure, a design that matches the house, the approvals your nation needs, structural design, building regulations approval and the build, carried out by vetted teams working under S&K.
Around Coulsdon we also work in Purley, Kenley and Banstead, and across the rest of Greater London. Postcode district in and near Coulsdon: CR5.
What it costs in Coulsdon
Most of the cost of an extension over a garage is set by its size and specification. For Coulsdon and the rest of London, our guide is £2,100–£3,060 per m² including VAT, so about £38,000–£55,000 for 3 m × 6 m of new first-floor space (18 m²). The fastest way to a firmer number is a free site visit, after which we price the design stage in writing.
| Spec | Per m² | 3 m × 6 m of new first-floor space (18 m²) |
|---|---|---|
| Essential | £1,930–£2,820 per m² | £35,000–£50,500 |
| Standard | £2,100–£3,060 per m² | £38,000–£55,000 |
| Premium | £2,520–£3,670 per m² | £45,500–£66,000 |
Planning and building regulations in Coulsdon
In England, most garages sit beside the house, so building over one makes a two-storey extension beyond a side wall, which always needs planning permission. If the garage is at the rear, the 3 m and 7 m rules for two-storey rear extensions apply, measured from the original house. A householder application costs £548 (or £575 for applications made from 8 December 2026).
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
Design points for Coulsdon homes
Fire separation
If the garage stays a garage, the floor between it and the room above, and any door into the house, must give fire separation under building regulations. That usually means fire-resisting plasterboard ceilings, sealed gaps and a fire door, which we design in from the start.
Checking the garage foundations
Garages are often built on shallow strip footings sized for a single-storey wall and a light roof. A trial hole shows their depth and condition, and the engineer decides whether they can carry two storeys or need underpinning or new foundations inside the garage.
How we'd run your project
Visit and first ideas
One of our team visits your house in Coulsdon, checks the walls, roof and drains, and sketches out options with you.
Drawings, then consent
We draw the scheme, check it against the rules in England, and take it through the right consent with the council.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.
Questions about extensions over a garage in Coulsdon
How long does an extension over a garage take?
Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.
How much does an extension over a garage cost in Coulsdon?
Our guide for London, which covers Coulsdon, is £2,100–£3,060 per m² including VAT. A typical project with 3 m × 6 m of new first-floor space (18 m²) comes to about £38,000–£55,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Which postcodes do you cover around Coulsdon?
We cover Coulsdon (CR5) and nearby places including Purley, Kenley and Banstead, plus the rest of Greater London. The first site visit is free.
How do I get into a room over the garage?
Usually through a new opening off the existing landing or a bedroom, so the stairs stay where they are. If the floor levels do not match, a step or two may be needed inside the new room. Where a landing opening is not practical, a new stair from a converted garage is an option.
Can my garage take a room on top?
Sometimes, but it needs checking. Many garages are built on shallow footings with thin walls, designed only for a single storey. We dig a trial hole and inspect the walls, and the structural engineer decides whether to reuse them, strengthen them, underpin the footings or build new foundations inside the garage.
Nearby
Close to Coulsdon? We work across the area, including:
Other extensions in Coulsdon
- Rear
- Side
- Wraparound
- Part two-storey
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Coulsdon · Extensions over a garage across Greater London
Book a free site visit in Coulsdon and we'll tell you what's possible, what approvals you need and what the design stage would cost.