Side extensions across County Down
Thinking about a side extension for your County Down home? Start with a free site visit: we measure up, check what the council will allow and give you honest guide figures on the day.
- Guide priceFrom £18,500 inc VAT
- PlanningDepends on the NI limits; checked at the survey
- Towns covered5
- Site visitFree, no obligation
Towns in County Down
Planning rules that apply in County Down
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.
Before any drawing is finalised we check whether the house is listed, in a conservation area or subject to an Article 4 direction.
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.
In Northern Ireland building control is run by the councils under the Building Regulations (Northern Ireland). We submit full plans or a building notice and book the inspections through to completion.
Applications are decided by your council, which handles local planning in Northern Ireland.
Who a side extension suits
- Detached and semi-detached houses with side land
- Houses where the rear garden is small
- Homes needing a utility, study or ground-floor bedroom
Councils often prefer side extensions to sit slightly back from the front of the house with a lower roof, so the original building still reads clearly. We design to those principles from the start to avoid redesigns.
Working in County Down
Towns we cover in County Down include Bangor, County Down, Newtownards, Newry, Banbridge, Downpatrick. 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.
How much does a side extension cost in County Down?
For County Down 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 County Down: £1,500 to £2,920 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 2.5 m × 5 m 12 m² | £18,500 – £23,000 | £21,000 – £27,500 | £26,500 – £35,500 |
| 3 m × 6 m 18 m² | £27,000 – £33,000 | £31,500 – £41,500 | £40,000 – £53,000 |
| 3 m × 8 m 24 m² | £36,000 – £43,500 | £42,000 – £55,000 | £53,500 – £70,500 |
Try the guide-price tool to see a range for your own size and finish.
What happens next
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
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
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.
Your questions about a side extension in County Down
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for County Down, 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 you cover all of County Down?
Yes, across the whole of County Down. Site visits are free and there is no obligation.
Who do I contract with for a side extension in County Down?
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.
Can I build over my driveway?
Yes, if the foundations work and you keep any parking the council requires. Drains and services under drives are common, so we check before design.
How much does a side extension cost?
Our guide range is about £1,500 to £2,920 per m² including VAT, depending on specification, so a standard 18 m² single-storey side extension lands around £31,500 to £41,500 in County Down.
Book a free site visit in County Down
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.