Extensions over a garage in Dagenham

Dagenham: the key facts for this kind of project.

Postcode districts: RM10
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: Elm Park (1.3 miles), Becontree (1.6 miles), Romford (1.9 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 Dagenham we also work in Elm Park, Becontree and Romford, and across the rest of Greater London. Postcode district in and near Dagenham: RM10.

What it costs in Dagenham

Our guide for London is £2,100–£3,060 per m² including VAT. On a project with 3 m × 6 m of new first-floor space (18 m²), that puts an extension over a garage in Dagenham at roughly £38,000–£55,000. 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	£1,930–£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 Dagenham

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 Dagenham 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

Start at your house
We come to your home in Dagenham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
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 Dagenham

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

Dagenham 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.

Which postcodes do you cover around Dagenham?

We cover Dagenham (RM10) and nearby places including Elm Park, Becontree and Romford, plus the rest of Greater London. The first site visit is free.

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

Our guide for London, which covers Dagenham, 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.

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.

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 Dagenham? We work across the area, including:

Other extensions in Dagenham

All two-storey extension services in Dagenham · Extensions over a garage across Greater London

Want a figure first? Try our guide price tool, then book a free visit to firm it up.