House extensions in County Down
Every type of house extension in County Down, from single-storey kitchen extensions to two-storey additions, side returns and orangeries. We design, handle the approvals and build.
- Towns listed5
- Price regionNorthern Ireland (×0.86)
- Planning rulesNorthern Ireland
- Postcode districts16
Towns we cover in County Down
Towns we cover here include Bangor, County Down, Newtownards, Newry, Banbridge.
Which extension suits a County Down home?
In Northern Ireland, extension projects follow the NI planning rules and council building control, which we account for from the first survey.
Start by comparing side extensions, annexe extensions and bungalow extensions: between them they cover most of the layouts we see requested for houses like these.
Planning rules 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.
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.
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.
County Down extension prices at a glance
Prices on this page use our Northern Ireland factor of ×0.86, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Single-storey rear extensions | 20 m² | £35,000 – £45,000 |
| Double-storey extensions | 32 m² | £49,500 – £65,000 |
| Conservatory replacement extensions | 14 m² | £25,500 – £33,500 |
| Extensions over a garage | 12 m² | £21,500 – £28,000 |
| Orangery extensions | 16 m² | £38,500 – £48,500 |
| Side return extensions | 11 m² | £22,500 – £28,500 |
Every extension type in County Down
- Porch extensions · from £3,400
- Home office extensions · from £13,500
- Pitched roof extensions · from £19,000
- Bedroom extensions · from £22,000
- Conservatory replacement extensions · from £17,000
- Double-storey extensions · from £32,500
- Timber frame extensions · from £18,000
- Kitchen extensions · from £23,000
- Extension plans and drawings · from £1,000
- Annexe extensions · from £47,000
- Flat roof extensions · from £18,000
- Utility and boot room extensions · from £12,000
- Side extensions · from £18,500
- Bungalow extensions · from £22,500
- Planning permission for extensions · from £300
- Glass box extensions · from £25,500
- Orangery extensions · from £25,500
- Side return extensions · from £15,000
- Building regulations for extensions · from £750
- Extensions over a garage · from £20,500
- Wraparound extensions · from £30,500
- Single-storey rear extensions · from £18,000
Neighbouring areas
Questions about extensions in County Down
How much does an extension cost in County Down?
With our Northern Ireland factor (×0.86), a standard-spec 20 m² single-storey extension is a guide £35,000 to £45,000 including VAT. Prices for every type are linked on this page.
Do I need planning permission for an extension in County Down?
Not always. It depends on the size, position and your property's history. In Northern Ireland some single-storey rear extensions are permitted development; larger ones need planning permission.
How long does an extension take in County Down?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Who do I contract with?
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.
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.