Extensions over a garage in Portrush

Quick reference for homeowners in Portrush.

Postcode districts: BT56
County / area: County Londonderry, 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: Portstewart (2.7 miles), Coleraine (4.4 miles), Ballymoney (10.2 miles)
Distance to Derry: about 29.5 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 BT56 in and around Portrush, along with neighbouring Portstewart, Coleraine and Ballymoney.

What it costs in Portrush

A guide price for Portrush: around £27,500–£40,500 for 3 m × 6 m of new first-floor space (18 m²). That works out at £1,540–£2,240 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	£1,420–£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 Portrush

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 Portrush homes

Checking the garage foundations

Garages are often built on shallow strip footings sized for a single-storey wall and a light roof. A trial hole shows their depth and condition, and the engineer decides whether they can carry two storeys or need underpinning or new foundations inside the garage.

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

Understand the brief
At your home in Portrush we agree what you need: bedroom count, bathroom, kitchen space, and how much garden you want to keep.
Drawings and permission
Our designers produce plans and elevations, then we take care of planning or permitted development checks with the council covering Portrush.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Finish and certify
Second fix, plastering and making good, then building control's final inspection and the completion paperwork.

Questions about extensions over a garage in Portrush

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

Portrush 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.

Which postcodes do you cover around Portrush?

We cover Portrush (BT56) and nearby places including Portstewart, Coleraine and Ballymoney, plus the rest of County Londonderry. The first site visit is free.

Who handles building control for a project in Portrush?

We handle it as part of the project. What's needed in Northern Ireland: building control approval from the local council under the Building Regulations (Northern Ireland), using the Technical Booklets. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

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.

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

Other towns near Portrush:

Other extensions in Portrush

All two-storey extension services in Portrush · Extensions over a garage across County Londonderry

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