Two-storey extensions for detached houses in Randalstown
Thinking about a two-storey extension for a detached house in Randalstown? We design it, take it through the approvals it needs and build it, with one team responsible from the first visit to the final certificate.
What we'd confirm first for a project in Randalstown.
- Postcode districts
- BT41
- County / area
- County Antrim, 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
- Antrim (4.2 miles), Ballymena (7.9 miles), Crumlin (County Antrim) (9.6 miles)
- Distance to Belfast
- about 18.3 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.
We cover postcode district BT41 in and around Randalstown, along with neighbouring Antrim, Ballymena and Crumlin (County Antrim).
What it costs in Randalstown
Our guide for Northern Ireland is £1,800–£2,420 per m² including VAT. On a project with a 3 m × 7 m footprint on two floors (42 m² of new floor space), that puts a two-storey extension for a detached house in Randalstown at roughly £76,000–£101,500. 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 Randalstown
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 Randalstown homes
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.
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 Randalstown, checks the walls, roof and drains, and sketches out options with you.
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.
Fixed price in writing
With approved drawings and calculations, we give you a fixed build price and a programme you can plan around.
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 Randalstown
How much does a two-storey extension for a detached house cost in Randalstown?
Our guide for Northern Ireland, which covers Randalstown, 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 Randalstown?
We cover Randalstown (BT41) and nearby places including Antrim, Ballymena and Crumlin (County Antrim), plus the rest of County Antrim. The first site visit is free.
Do I need planning permission for a two-storey extension for a detached house in Randalstown?
Randalstown is in Northern Ireland. 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.
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.
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.
Nearby
Close to Randalstown? We work across the area, including:
Other extensions in Randalstown
- Rear
- Side
- Wraparound
- Part two-storey
- Over a garage
- First floor
- Semi-detached
- Kitchen and bedrooms
- Bedroom and en-suite
All two-storey extension services in Randalstown · Two-storey extensions for detached houses across County Antrim
Want a figure first? Try our guide price tool, then book a free visit to firm it up.