Extensions over a garage in Birmingham

Before you start in Birmingham, here's what applies.

Postcode districts: B1, B2, B3, B4, B5, B12 and nearby districts
County / area: West Midlands, England
Price region: West Midlands
Guide price: £31,500–£46,000 (£1,750–£2,550 per m²)
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Nearest towns: Aston (1.5 miles), Hockley (1.5 miles), Smethwick (2.9 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 districts B1, B2, B3, B4, B5, B12 and nearby districts in and around Birmingham, along with neighbouring Aston, Hockley and Smethwick.

What it costs in Birmingham

Most of the cost of an extension over a garage is set by its size and specification. For Birmingham and the rest of the West Midlands, our guide is £1,750–£2,550 per m² including VAT, so about £31,500–£46,000 for 3 m × 6 m of new first-floor space (18 m²). Steelwork for wide openings is the item most likely to move the figure; we'll know once the engineer has designed it.

Spec	Per m²	3 m × 6 m of new first-floor space (18 m²)
Essential	£1,610–£2,350 per m²	£29,000–£42,000
Standard	£1,750–£2,550 per m²	£31,500–£46,000
Premium	£2,100–£3,060 per m²	£38,000–£55,000

Planning and building regulations in Birmingham

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 Birmingham homes

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.

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.

How we'd run your project

Start at your house
We come to your home in Birmingham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
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 it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Questions about extensions over a garage in Birmingham

How much does an extension over a garage cost in Birmingham?

Our guide for the West Midlands, which covers Birmingham, is £1,750–£2,550 per m² including VAT. A typical project with 3 m × 6 m of new first-floor space (18 m²) comes to about £31,500–£46,000. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Do I need planning permission for an extension over a garage in Birmingham?

Birmingham 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.

Who handles building regulations for a project in Birmingham?

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.

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.

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.

Nearby

Nearby towns we cover for extensions over a garage:

Other extensions in Birmingham

All two-storey extension services in Birmingham · Extensions over a garage across the West Midlands

Send us your postcode and a few details. We'll get back to you to arrange a visit and talk through your options.