Belfast, County Antrim
Single-storey rear extension in Belfast
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. If you live in Belfast and want to know what a single-storey rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
Belfast sits in County Antrim, with postcode districts including BT3, BT5, BT7 and BT9. A depth of 3 to 4 metres keeps many single-storey rear extensions in Belfast within permitted development, subject to the house's planning history.
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 single-storey rear extension cost in Belfast?
A single-storey rear extension in Belfast is priced at £1,650–£2,700 per square metre including VAT as a guide, before kitchen fit-out and fees. 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 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission for a single-storey rear extension in Belfast?
The planning route for a single-storey rear extension in Belfast is set by Northern Ireland's householder rules and your council.
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.
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?
Belfast has terraces near the centre, semis on the edges and many detached houses and bungalows in the surrounding countryside, where plots are often generous.
How a single-storey rear extension in Belfast comes together
Look round and measure
A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Paperwork handled
Planning or permitted development, building control approval, structural design and neighbour agreements are all handled by us.
Build and sign-off
We build to the approved drawings with regular updates, then hand over the building control completion certificate and any guarantees from suppliers.
Single-storey rear extensions near Belfast
Neighbouring places we cover include Castlereagh (2.3 miles) and Newtownabbey (4.4 miles).
- Single-storey rear extension in Castlereagh
- Single-storey rear extension in Newtownabbey
- Single-storey rear extension in Holywood
- Single-storey rear extension in Dundonald
- Single-storey rear extension in Lisburn
Other work in Belfast:
FAQ
Single-storey rear extension questions in Belfast
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.
Do I need a party wall agreement?
Northern Ireland has no Party Wall Act; we agree any shared-wall work with your neighbour in writing.
Does it add value to the house?
Nationwide's October 2025 house price research found that a 10% increase in floor area is linked to about 5% higher value on average. It is a guide, not a promise; local agents can tell you what extended homes on your street sell for.
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.
Is the site visit in Belfast free?
Yes. We visit, measure up and talk through the options with no cost and no obligation.
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.