Single-storey rear extensions in Derry/Londonderry: design, approvals and build
If you live in Derry/Londonderry and want more space without moving, a single-storey extension is one of the most practical ways to get it. We handle the drawings, approvals and the build.
- Guide price in Derry/LondonderryFrom £18,000 inc VAT
- PlanningNI permitted development (rear 3–4 m) or planning
- Build time10–16 weeks on site
- Postcode districtsBT48
Do I need planning permission in Derry/Londonderry?
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.
In a conservation area or area of townscape character the permitted development rights are more limited, listed homes need listed building consent, and if rights have been removed by a condition, any extension needs an application.
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.
Applications are decided by your council, which handles local planning in Northern Ireland.
Guide prices for Derry/Londonderry
Labour and material costs vary across the UK, so for Derry/Londonderry we use our Northern Ireland factor (×0.86). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Derry/Londonderry: £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.
When a single-storey extension makes sense
- Homeowners who want open-plan living onto the garden
- Terraced houses that want a deeper kitchen across the full width
- Semi-detached and detached houses with a usable rear garden
Depth is the big decision. Every extra metre adds floor area but also takes garden and can push you out of permitted development. We draw the room at two or three depths so you can see the trade-off in space, light and cost before anything is fixed.
Working in Derry/Londonderry
Site visits are available across Derry/Londonderry (BT48). We also work in nearby Limavady (15 miles), Coleraine (27 miles), Magherafelt (31 miles).
In Northern Ireland, extension projects follow the NI planning rules and council building control, which we account for from the first survey.
From first visit to completion
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
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Common questions in Derry/Londonderry
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Derry/Londonderry, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
How long does a single-storey extension take to build in Derry/Londonderry?
On site, typically 10 to 16 weeks once approvals are in place. Before that, allow 4–12 weeks design and approvals.
Do I need building regulations approval in Derry/Londonderry?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Can I stay in the house during the build?
Usually yes. Most of the work happens outside until the final weeks, when we open the rear wall. We plan that stage carefully and seal the opening with a temporary screen to keep dust down.
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 Derry/Londonderry, plus design and council fees.
Book a free site visit in Derry/Londonderry
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.