Belfast, County Antrim
Semi-detached rear extension in Belfast
Single or two-storey extensions for semi-detached houses, with side access and one party wall. If you live in Belfast and want to know what a semi-detached rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Belfast is covered from our County Antrim round, including BT3, BT5, BT7 and BT9. Semi-detached houses are common across County Antrim, and their side access makes rear extensions quicker to build.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Belfast?
Guide prices for a semi-detached rear extension in Belfast start from our Northern Ireland rate of £1,650–£2,700 per square metre, including VAT. Northern Ireland prices are the lowest in our range.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £20,000–£32,500 |
| 4 m wide × 5 m deep (20 m²) | £33,000–£54,000 |
| 4 m wide × 6 m deep (24 m²) | £39,500–£64,500 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a semi-detached rear extension in Belfast?
Planning for a semi-detached rear extension in Belfast follows the Northern Irish householder rules.
In Northern Ireland the Planning (General Permitted Development) Order (Northern Ireland) 2015 allows a single-storey rear extension of up to 3 metres on an attached house or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres within 2 metres of a boundary. Building control approval from the council is still required.
In Northern Ireland a rear extension of more than one storey can be permitted development if it projects no more than 3 metres and stays at least 7 metres from the rear boundary. Two-storey extensions in conservation areas, and most larger schemes, need planning permission from the council.
Northern Ireland has no larger-extension prior approval route; anything beyond permitted development needs a planning application.
Conservation areas, Areas of Outstanding Natural Beauty and listed buildings restrict permitted development in Northern Ireland. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Belfast like to extend?
Semis and detached houses are typical of Belfast, and many have room for a rear extension within Northern Ireland's permitted development limits.
How a semi-detached rear extension in Belfast comes together
Free site visit
We measure the house and garden, look at the back wall, drainage and boundaries, and talk through what you want from the space.
Design and guide price
Two or three layout options with a guide price for each, so you choose the design knowing what it costs.
Approvals
Permitted development check or planning application, then building control drawings to the Northern Ireland Technical Booklets and structural calculations, plus a written agreement with neighbours for any shared-wall work.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Belfast
We also build rear extensions for semi-detached houses in nearby Castlereagh (2.3 miles) and Newtownabbey (4.4 miles).
- Semi-detached rear extension in Castlereagh
- Semi-detached rear extension in Newtownabbey
- Semi-detached rear extension in Holywood
- Semi-detached rear extension in Dundonald
- Semi-detached rear extension in Lisburn
Other work in Belfast:
FAQ
Semi-detached rear extension questions in Belfast
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
Single or two-storey on a semi?
Two-storey if you need bedrooms, single-storey if you need a bigger kitchen. Planning risk is lower for single-storey.
How long does a rear extension take to build in Belfast?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.
Do I need planning permission for a rear extension in Belfast?
Often not for a single-storey rear extension of up to 3 metres (4 metres detached) under Northern Ireland's permitted development rules, outside conservation areas.
Can you match the brick or stone on my Belfast house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.