Extensions over a garage in Holywood

What we'd confirm first for a project in Holywood.

Postcode districts: BT18
County / area: County Down, Northern Ireland
Price region: Northern Ireland
Guide price: £27,500–£40,500 (£1,540–£2,240 per m²)
Approval route: Planning permission is needed: permitted development side extensions in Northern Ireland can't be more than 4 m high, which rules out two storeys.
Nearest towns: Dundonald (3.4 miles), Newtownabbey (3.7 miles), Jordanstown (4.3 miles)
Distance to Bangor (County Down): about 6.4 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.

Holywood sits about 6.4 miles from Bangor (County Down). Closer to home, Dundonald is 3.4 miles away and Newtownabbey 3.7 miles.

What it costs in Holywood

Our guide for Northern Ireland is £1,540–£2,240 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 Holywood at roughly £27,500–£40,500. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	3 m × 6 m of new first-floor space (18 m²)
Essential	£1,420–£2,060 per m²	£25,500–£37,000
Standard	£1,540–£2,240 per m²	£27,500–£40,500
Premium	£1,850–£2,690 per m²	£33,500–£48,500

Planning and building control in Holywood

In Northern Ireland, permitted development for two-storey work is set out for rear extensions, so building over a side garage normally needs a planning application, which costs £347 per dwelling. Councils aim for an average of 15 weeks for local applications. Building control approval is also needed, including fire separation if the garage stays in use.

Approval in Northern Ireland: Planning application for works to a house: £347. Councils aim to decide local applications within an average of 15 weeks; many take longer.

Building control: Building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets.

Design points for Holywood homes

Floor levels and headroom

Garage floors are often lower than the house, and the new first floor may not line up with the existing landing. We set the floor level to avoid awkward steps upstairs, while keeping enough headroom in the garage below for a car or storage.

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.

How we'd run your project

Measure and listen
A visit to Holywood to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Holywood and deal with any questions from the planning officer.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
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 Holywood

Which postcodes do you cover around Holywood?

We cover Holywood (BT18) and nearby places including Dundonald, Newtownabbey and Jordanstown, plus the rest of County Down. The first site visit is free.

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

Holywood is in Northern Ireland. Planning permission is needed: permitted development side extensions in Northern Ireland can't be more than 4 m high, which rules out two storeys.

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

Our guide for Northern Ireland, which covers Holywood, is £1,540–£2,240 per m² including VAT. A typical project with 3 m × 6 m of new first-floor space (18 m²) comes to about £27,500–£40,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

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.

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.

Nearby

The same service in neighbouring towns:

Other extensions in Holywood

All two-storey extension services in Holywood · Extensions over a garage across County Down

The quickest next step is a visit. We'll look at your house in Holywood and give you an honest view of the options.