Belfast single-storey extensions, designed and built
We design and build single-storey extensions for houses in Belfast, with a written price once the survey and design are done and one point of contact throughout.
- Guide price in BelfastFrom £18,000 inc VAT
- PlanningNI permitted development (rear 3–4 m) or planning
- Build time10–16 weeks on site
- Postcode districtsBT1, BT2, BT6, BT7, BT12
What is included
- Walls, steel beams and the new opening into the house
- Flat or pitched roof, rooflights or lantern
- Doors, windows, insulation, plastering and first fix to finish
- Building regulations drawings and structural calculations
- Foundations, drainage and groundworks
- Planning route checked and the right approval obtained
How much does a single-storey extension cost in Belfast?
Prices below are for Belfast, using the Northern Ireland factor of ×0.86. They are guide ranges including VAT for the build only, not a quote.
Typical rates in Belfast: £1,500 to £2,920 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m 12 m² | £18,000 – £21,500 | £21,000 – £27,000 | £26,500 – £35,500 |
| 4 m × 5 m 20 m² | £30,000 – £35,500 | £35,000 – £45,000 | £44,500 – £58,500 |
| 5 m × 6 m 30 m² | £45,000 – £53,000 | £52,500 – £67,500 | £67,000 – £88,000 |
For a figure based on your own dimensions, use our guide-price tool.
Will the council need to approve it?
In Northern Ireland the Planning (General Permitted Development) Order 2015 lets some single-storey rear extensions go ahead without planning permission, up to 3 m on a semi-detached or terraced house and 4 m on a detached house, within height and boundary limits. Larger, side and two-storey extensions normally need planning permission from the council, and building control approval is separate.
The planning position for a specific Belfast address depends on its history and any designations, which is why we check it at the first visit.
Northern Ireland has no Party Wall Act. Where work is on or close to a shared boundary, we agree access and protection with your neighbour in writing before work starts.
Building close to a public sewer needs the agreement of NI Water, which we check during design.
Applications are decided by your council, which handles local planning in Northern Ireland.
Covering Belfast
We cover Belfast and the postcode districts BT1, BT2, BT6, BT7, BT12, BT13. The same team covers Castlereagh (2 miles), Newtownabbey (4 miles), Lisburn (7 miles), Carrickfergus (10 miles), all within easy reach.
For homes towards County Down, Newtownards is around 9 miles away. In Northern Ireland, extension projects follow the NI planning rules and council building control, which we account for from the first survey.
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Single-storey extension questions answered
Do you cover all of Belfast?
Yes. We cover Belfast and the surrounding parts of County Antrim. Site visits are free and there is no obligation.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Belfast, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Do I need building regulations approval in Belfast?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
How much does a single-storey extension cost per square metre?
Our guide range is about £1,500 to £2,920 per m² including VAT, depending on specification. A standard-spec 4 m × 5 m room usually lands at £35,000 to £45,000 in Belfast, plus design and council fees.
Flat roof or pitched roof?
Flat roofs give more headroom inside and suit lanterns and rooflights; pitched roofs can blend better with older houses. Both meet building regulations when built properly. See our flat roof and pitched roof pages for the details.
Book a free site visit in Belfast
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.