Two-storey rear extensions in Carryduff

Carryduff: the key facts for this kind of project.

Postcode districts: BT8
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: Castlereagh (3.8 miles), Belfast (5.7 miles), Lisburn (6 miles)
Distance to Bangor (County Down): about 13.2 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.

We cover postcode district BT8 in and around Carryduff, along with neighbouring Castlereagh, Belfast and Lisburn.

What it costs in Carryduff

For budgeting in Carryduff, allow around £49,500–£66,500 for a two-storey rear extension with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). That's based on £1,760–£2,380 per m² including VAT for Northern Ireland. 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	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 Carryduff

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 Carryduff 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.

Opening up the ground floor

Knocking through the old rear wall means steel beams to carry the first floor and roof above. The structural engineer sets the beam sizes, padstones and any posts, and we plan them early so the open-plan layout you want is the one that gets built.

How we'd run your project

Start at your house
We come to your home in Carryduff, 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 Northern Ireland before drawing in detail.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
Build and sign-off
Vetted teams working under S&K build the extension, and we arrange the building control completion certificate at the end.

Questions about two-storey rear extensions in Carryduff

Who handles building control for a project in Carryduff?

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 much does a two-storey rear extension cost in Carryduff?

Our guide for Northern Ireland, which covers Carryduff, 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 Carryduff?

We cover Carryduff (BT8) and nearby places including Castlereagh, Belfast and Lisburn, plus the rest of County Down. The first site visit is free.

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.

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

Nearby towns we cover for two-storey rear extensions:

Other extensions in Carryduff

All two-storey extension services in Carryduff · Two-storey rear extensions across County Down

Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Carryduff.