County Down
Permitted development rear extensions in County Down
Designing to the no-application limits, with a certificate of lawfulness of proposed use or development as proof. Across County Down we handle the whole rear extension: survey, drawings, the planning route, building control and the build. Towns we cover here include Bangor, Castlereagh and Newtownards.

County Down 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 much does a permitted development rear extension cost in County Down?
Guide prices for a permitted development rear extension in County Down start from our Northern Ireland rate of £1,650–£2,700 per square metre, including VAT. 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 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission in County Down?
Northern Ireland's permitted development rules allow a single-storey rear extension of 3 metres on terraced and semi-detached houses and 4 metres on detached houses, with a 4 metre height limit. Listed buildings, conservation areas and houses with removed rights need planning permission from the council.
Northern Ireland's 2015 Order allows a two-storey rear extension of up to 3 metres where at least 7 metres is left to the rear boundary. Anything larger, or in a conservation area, needs a planning application to the council.
Conservation areas, Areas of Outstanding Natural Beauty and listed buildings restrict permitted development in Northern Ireland.
Where in County Down do we work?
FAQ
Questions people ask
Is permitted development the same as planning permission?
No; it is a national grant of permission for work within set limits, so no application is needed.
Do I still need Building Regulations?
Yes, always.
How long does a certificate of lawfulness of proposed use or development take?
Councils should decide within 8 weeks.
Do you cover all of County Down?
We cover 8 towns and districts in County Down, including Bangor, Castlereagh and Newtownards.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.