Double-storey extensions in Derry/Londonderry: design, approvals and build
If you live in Derry/Londonderry and want more space without moving, a double-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 £32,500 inc VAT
- PlanningUsually needs planning permission
- Build time16–24 weeks on site
- Postcode districtsBT48
Working in Derry/Londonderry
Our survey diary covers Derry/Londonderry, including BT48. We also work in nearby Limavady (15 miles), Coleraine (27 miles), Magherafelt (31 miles).
Strabane, in County Tyrone, is roughly 13 miles from Derry/Londonderry and also on our list. Northern Ireland's housing ranges from city terraces to large numbers of detached houses and bungalows on rural plots, many in render, where single-storey extensions fit easily.
When a double-storey extension makes sense
- Homeowners who would otherwise consider moving
- Houses with enough distance to the rear or side boundary
- Growing families who need a bedroom as well as a bigger kitchen
The roof is what makes a two-storey extension look right or wrong. We match the pitch and materials of the main house wherever possible and plan the upstairs layout around the existing landing so the new rooms feel original rather than bolted on.
Planning rules that apply 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.
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.
How much does a double-storey extension cost in Derry/Londonderry?
For Derry/Londonderry we adjust our national guide rates by ×0.86, the factor we use for Northern Ireland. Figures include VAT; your written quote after the survey replaces them.
Typical rates in Derry/Londonderry: £1,330 to £2,580 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m, two floors 24 m² | £32,500 – £39,500 | £37,000 – £49,000 | £47,000 – £62,000 |
| 4 m × 4 m, two floors 32 m² | £42,500 – £51,000 | £49,500 – £65,000 | £63,000 – £83,000 |
| 4 m × 6 m, two floors 48 m² | £63,500 – £76,500 | £74,000 – £97,500 | £94,500 – £124,000 |
Try the guide-price tool to see a range for your own size and finish.
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
We visit your Derry/Londonderry home, measure up, talk through what you want and check the planning position.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
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
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.
How long does a double-storey extension take to build in Derry/Londonderry?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 8–16 weeks design and approvals.
Who do I contract with for a double-storey extension in Derry/Londonderry?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Is a two-storey extension cheaper per square metre?
Usually. Our guide range is about £1,330 to £2,580 per m² of new floor area including VAT, compared with £1,500 to £2,920 per m² for single-storey work, because the foundations and roof are shared across two floors.
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.