Extensions over a garage in East Grinstead
Thinking about an extension over a garage in East Grinstead? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
Quick reference for homeowners in East Grinstead.
- Postcode districts
- RH19
- County / area
- West Sussex, England
- Price region
- South East England
- Guide price
- £34,500–£50,500 (£1,930–£2,800 per m²)
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Nearest towns
- Horley (7.5 miles), Crawley (7.7 miles), Crowborough (8.5 miles)
- Distance to Crawley
- about 7.7 miles
- First visit
- Free, no obligation
About an extension over a garage
An extension over a garage is a new first-floor room built on top of an existing attached garage, usually a bedroom, en-suite or study. It uses a footprint you already have, so it adds floor space without taking any garden. The garage walls and foundations often need strengthening or replacing to carry the new floor.
We cover postcode district RH19 in and around East Grinstead, along with neighbouring Horley, Crawley and Crowborough.
What it costs in East Grinstead
In South East England, which includes East Grinstead, we'd expect an extension over a garage to cost around £34,500–£50,500 for 3 m × 6 m of new first-floor space (18 m²), or £1,930–£2,800 per m² including VAT. Keep a contingency of around 10% for things nobody can see until the ground is opened up.
| Spec | Per m² | 3 m × 6 m of new first-floor space (18 m²) |
|---|---|---|
| Essential | £1,770–£2,580 per m² | £32,000–£46,500 |
| Standard | £1,930–£2,800 per m² | £34,500–£50,500 |
| Premium | £2,310–£3,370 per m² | £41,500–£60,500 |
Planning and building regulations in East Grinstead
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 East Grinstead homes
Matching the house
A room over a garage usually sits beside the front of the house in full view, so roof form, ridge height, windows and brick matter. Setting the front wall and ridge back slightly from the main house usually helps it look as if it belongs.
Garage walls and the door opening
Garage walls are often a single skin of brick or block with piers, and the wide door opening needs a beam over it. Many over-garage extensions need new inner walls or a steel frame to carry the floor and to insulate properly, which we confirm before the design is fixed.
How we'd run your project
Measure and listen
A visit to East Grinstead to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.
Questions about extensions over a garage in East Grinstead
Do I need planning permission for an extension over a garage in East Grinstead?
East Grinstead is in England, so England planning rules apply. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.
How much does an extension over a garage cost in East Grinstead?
Our guide for South East England, which covers East Grinstead, is £1,930–£2,800 per m² including VAT. A typical project with 3 m × 6 m of new first-floor space (18 m²) comes to about £34,500–£50,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.
Who handles building regulations for a project in East Grinstead?
We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.
Do I need to convert the garage as well?
No. You can keep the garage for parking or storage and build only the room above, as long as the floor between them and any door into the house meet fire separation rules. Converting the garage at the same time is often good value, because the walls and foundations may be upgraded anyway.
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
Other towns near East Grinstead:
Other extensions in East Grinstead
- Rear
- Side
- Wraparound
- Part two-storey
- First floor
- Semi-detached
- Detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in East Grinstead · Extensions over a garage across West Sussex
Tell us about your house in East Grinstead and we'll call you back to arrange a free, no-obligation visit.