What permitted development means
Permitted development rights let you make certain changes to a house without a full planning application, as long as you stay within set limits. They apply to houses, not flats or maisonettes, and they can be removed or restricted in some areas (for example by an Article 4 direction), so it is always worth checking with your council first.
The limits are measured from the original house: the house as it was first built, or as it stood on 1 July 1948 if it is older. Previous extensions by you or earlier owners count towards the limits.
Single-storey rear extensions
- Can extend up to 4 metres beyond the original rear wall of a detached house, or 3 metres for any other house.
- Maximum height of 4 metres.
- Through the prior approval process (sometimes called the larger home extension scheme), you can go up to 8 metres (detached) or 6 metres (other houses). Your council notifies your neighbours and considers any objections before deciding.
- The prior approval option is not available on designated land, such as conservation areas, National Parks or Areas of Outstanding Natural Beauty.
Side extensions
- Single storey only, with a maximum height of 4 metres.
- Width no more than half the width of the original house.
- On designated land, side extensions always need planning permission.
Two-storey extensions
- No more than 3 metres beyond the original rear wall.
- Must be at least 7 metres from the boundary opposite the rear wall.
- Roof pitch should match the existing house as far as practicable.
- Upper-floor windows in a side wall must be obscure-glazed and non-opening unless the opening part is more than 1.7 metres above the floor.
- Side extensions of more than one storey always need planning permission.
Rules that apply to every extension
- No higher than the highest part of the existing roof, and the eaves no higher than the existing eaves.
- Within 2 metres of a boundary, the eaves can be no higher than 3 metres.
- Extensions and other buildings must not cover more than half the land around the original house.
- No extension forward of the principal elevation, or of a side elevation that fronts a road.
- Materials should be similar in appearance to the existing house.
- Verandas, balconies and raised platforms are not permitted development.
When you need to apply
- Your extension goes beyond any of the limits above.
- You live in a flat or maisonette.
- The house is a listed building (you will also need listed building consent).
- Your permitted development rights have been removed by a planning condition or Article 4 direction.
Even if you do not need permission, you can apply for a lawful development certificate to confirm that your extension is lawful. It is optional, but useful proof when you come to sell.
Planning is only half the story
Whether or not you need planning permission, most extensions still need Building Regulations approval, and work near a shared wall or boundary may need a party wall notice.
Wales, Scotland and Northern Ireland have their own rules. This guide covers England. If you live elsewhere in the UK, check with your local council.
Last updated: 14 October 2026
