Two-storey rear extensions in Holywood

Holywood: the key facts for this kind of project.

Postcode districts: BT18
County / area: County Down, Northern Ireland
Price region: Northern Ireland
Guide price: £49,500–£66,500 (£1,760–£2,380 per m²)
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.
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 a two-storey rear extension

A two-storey rear extension is a new two-floor addition built onto the back of your house, usually giving a larger kitchen or living space on the ground floor and one or two bedrooms or a bathroom above. Because both floors share one set of foundations and one roof, it adds a lot of floor space for the garden it uses. In some cases it can be built under permitted development, depending on where you live.

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

Guide prices for two-storey rear extensions in Northern Ireland are around £1,760–£2,380 per m² of new floor space, including VAT. For a typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), that's roughly £49,500–£66,500. Professional fees for drawings and the structural engineer are listed separately on our prices page.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,620–£2,190 per m²	£45,500–£61,000
Standard	£1,760–£2,380 per m²	£49,500–£66,500
Premium	£2,110–£2,850 per m²	£59,000–£80,000

Planning and building control in Holywood

In Northern Ireland, a two-storey rear extension can be permitted development if it goes no more than 3 m beyond the original rear wall and stays at least 7 m from the rear boundary, with conditions on height, materials and roof pitch. Upper side windows within 15 m of a neighbouring boundary must be obscure-glazed and non-opening. Otherwise a planning application costs £347 per dwelling.

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

Foundations and drains

Foundations for two storeys carry more load than a single storey and may need to go deeper near trees or on clay. Rear extensions often sit near drains, so we check sewer records early, as building over or near a public sewer may need the water company's agreement.

Depth and neighbours' light

Councils check that a two-storey rear extension does not take too much light or outlook from neighbouring windows, and many use a 45-degree line drawn from the nearest habitable window. We test this at sketch stage, so the depth you are shown is one that can realistically be approved.

How we'd run your project

Visit and first ideas
One of our team visits your house in Holywood, checks the walls, roof and drains, and sketches out options with you.
Design and approvals
We draw the extension and check it against the rules for Northern Ireland, then apply for planning permission or a certificate of lawfulness, whichever fits.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about two-storey rear extensions in Holywood

How long does a two-storey rear extension take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils aim to decide local applications within an average of 15 weeks; many take longer), 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.

Do I need planning permission for a two-storey rear extension in Holywood?

Holywood is in Northern Ireland. It may be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary.

How much does a two-storey rear extension cost in Holywood?

Our guide for Northern Ireland, which covers Holywood, is £1,760–£2,380 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £49,500–£66,500. 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 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.

Will a two-storey rear extension block my neighbour's light?

It can if it is too deep or too close to the boundary, which is why councils look closely at its effect on neighbouring windows and gardens. We test the design against light and outlook early, keep the first floor shorter or set in where needed, and use a hipped roof to reduce bulk on the boundary side.

Nearby

The same service in neighbouring towns:

Other extensions in Holywood

All two-storey extension services in Holywood · Two-storey rear extensions 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.