Two-storey extensions for detached houses in Dundonald

The basics for Dundonald at a glance.

Postcode districts: BT16
County / area: County Down, 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: Holywood (3.4 miles), Comber (3.7 miles), Castlereagh (3.7 miles)
Distance to Bangor (County Down): about 7 miles
First visit: Free, no obligation

About a two-storey extension for a detached house

A two-storey extension for a detached house is a two-floor addition to the side, rear or both of a house that stands on its own plot. Detached houses often have room on more than one side, so there is more choice of layout and fewer shared-wall issues. The design still needs to respect boundaries, neighbours' windows and the look of the house.

Around Dundonald we also work in Holywood, Comber and Castlereagh, and across the rest of County Down. Postcode district in and near Dundonald: BT16.

What it costs in Dundonald

Expect a two-storey extension for a detached house in Dundonald to land somewhere around £76,000–£101,500 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). Our Northern Ireland guide rate is £1,800–£2,420 per m², including VAT. Design fees, structural calculations and approval fees are separate and listed on our prices page.

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 Dundonald

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 Dundonald 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.

Keeping it subordinate

Large detached houses can take a large extension, but councils still expect it to look secondary to the main house. A lower ridge, a modest set-back at the front and matching materials keep the proportions right, even on a wide plot.

How we'd run your project

Visit and first ideas
One of our team visits your house in Dundonald, checks the walls, roof and drains, and sketches out options with you.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Questions about two-storey extensions for detached houses in Dundonald

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

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

We cover Dundonald (BT16) and nearby places including Holywood, Comber and Castlereagh, plus the rest of County Down. The first site visit is free.

How long does a two-storey extension for a detached house 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.

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 Dundonald

All two-storey extension services in Dundonald · Two-storey extensions for detached houses across County Down

Want a figure first? Try our guide price tool, then book a free visit to firm it up.