Extensions over a garage in Altrincham

The basics for Altrincham at a glance.

Postcode districts: WA14
County / area: Greater Manchester, England
Price region: North West England
Guide price: £30,000–£43,500 (£1,660–£2,420 per m²)
Approval route: Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Nearest towns: Hale (Greater Manchester) (0.9 miles), Timperley (1.1 miles), Hale Barns (1.9 miles)
Distance to Manchester: about 7.9 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.

Around Altrincham we also work in Hale (Greater Manchester), Timperley and Hale Barns, and across the rest of Greater Manchester. Postcode district in and near Altrincham: WA14.

What it costs in Altrincham

A guide price for Altrincham: around £30,000–£43,500 for 3 m × 6 m of new first-floor space (18 m²). That works out at £1,660–£2,420 per m² of new floor space, including VAT at 20%. 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	£1,530–£2,230 per m²	£27,500–£40,000
Standard	£1,660–£2,420 per m²	£30,000–£43,500
Premium	£1,990–£2,910 per m²	£36,000–£52,500

Planning and building regulations in Altrincham

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 Altrincham 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.

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 Altrincham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Altrincham.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
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 Altrincham

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 Altrincham?

Our guide for North West England, which covers Altrincham, is £1,660–£2,420 per m² including VAT. A typical project with 3 m × 6 m of new first-floor space (18 m²) comes to about £30,000–£43,500. 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 Altrincham?

We cover Altrincham (WA14) and nearby places including Hale (Greater Manchester), Timperley and Hale Barns, plus the rest of Greater Manchester. The first site visit is free.

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 I add an en-suite above the garage?

Yes, and it is a common choice for a main bedroom. The en-suite needs an extract fan under Part F, a route for the soil pipe down to the drains and enough fall for the waste, which can be harder over a garage. We plan the pipe route through the garage or an outside wall early.

Nearby

Close to Altrincham? We work across the area, including:

Other extensions in Altrincham

All two-storey extension services in Altrincham · Extensions over a garage across Greater Manchester

Tell us about your house in Altrincham and we'll call you back to arrange a free, no-obligation visit.