Two-storey extensions for detached houses in Derry

Useful details for planning a two-storey extension for a detached house in Derry.

Postcode districts: BT48
County / area: County Londonderry, Northern Ireland
Price region: Northern Ireland
Guide price: £76,000–£101,500 (£1,800–£2,420 per m²)
Approval route: Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); most others need planning permission.
Nearest towns: New Buildings (3.1 miles), Culmore (4 miles), Eglinton (5.2 miles)
First visit: Free, no obligation

About a two-storey extension for a detached house

This service suits you if you own a detached house and want a substantial amount of extra space, whether a side extension over a drive, a rear extension into the garden or a wraparound. You get a survey of the whole plot, options that compare layouts and costs, the approvals your nation needs, structural design and the build, carried out by vetted teams working under S&K.

Around Derry we also work in New Buildings, Culmore and Eglinton, and across the rest of County Londonderry. Postcode district in and near Derry: BT48.

What it costs in Derry

Using our Northern Ireland rates, a two-storey extension for a detached house with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £76,000–£101,500, including VAT. Bigger or more glazed designs cost more per m². Kitchens, bathroom fittings and flooring are priced separately so you can compare like with like.

Spec	Per m²	A 3 m × 7 m footprint on two floors (42 m² of new floor space)
Essential	£1,660–£2,230 per m²	£69,500–£93,500
Standard	£1,800–£2,420 per m²	£76,000–£101,500
Premium	£2,160–£2,900 per m²	£91,000–£122,000

Planning and building control in Derry

In Northern Ireland, a two-storey rear extension on a detached house can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with height, materials and roof pitch conditions. Side and wraparound designs normally need a planning application, which 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 Derry homes

Choosing the best side

On a detached house you can often extend on either side or the rear. We look at orientation for daylight, where the stairs and landing are, the distance to each boundary, drains and trees, so the extension goes where it adds the most useful space.

Larger spans and steelwork

Bigger extensions often mean wider openings and longer spans, which need more steel and sometimes a steel frame. The engineer designs these early, because the size of the steel affects ceiling heights, floor depths and the cost.

How we'd run your project

Visit and first ideas
One of our team visits your house in Derry, checks the walls, roof and drains, and sketches out options with you.
Get it approved
Once you're happy with the design we submit it to the council for Derry and deal with any questions from the planning officer.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about two-storey extensions for detached houses in Derry

How much does a two-storey extension for a detached house cost in Derry?

Our guide for Northern Ireland, which covers Derry, is £1,800–£2,420 per m² including VAT. A typical project with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £76,000–£101,500. 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 Derry?

We cover Derry (BT48) and nearby places including New Buildings, Culmore and Eglinton, plus the rest of County Londonderry. The first site visit is free.

Who handles building control for a project in Derry?

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.

Can I extend a detached house on both sides?

Sometimes. With planning permission, a council may accept extensions on both sides if the house stays well proportioned and keeps gaps to the boundaries. It is more common to extend on one side and the rear, or with a wraparound. We look at the plot as a whole before suggesting more than one extension.

Is a detached house extension a better investment than moving?

It often costs less than the gap between your house and a larger one nearby, once property tax, legal fees and removal costs are counted, but that depends on your area. Extending also has limits: every street has a ceiling price. We give you build costs so you can compare them with local asking prices.

Nearby

The same service in neighbouring towns:

Other extensions in Derry

All two-storey extension services in Derry · Two-storey extensions for detached houses across County Londonderry

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