In England, many single storey rear extensions do not need planning permission. Under permitted development you can usually extend up to 3 metres from the original rear wall of a terraced or semi-detached house, or 4 metres for a detached house, with a maximum height of 4 metres. Prior approval can extend this to 6 metres and 8 metres. Two-storey, wrap-around and most front extensions need full planning permission, and every extension needs Building Regulations approval.
Single storey rear extensions
- Up to 3 m beyond the original rear wall for attached houses, or 4 m for detached houses.
- Maximum height 4 m.
- If within 2 m of a boundary, eaves height no more than 3 m.
- The extension and other buildings together must not cover more than half the land around the original house.
- Materials similar in appearance to the existing house.
"Original" means the house as it was first built, or as it stood on 1 July 1948 if older. Earlier extensions count towards the limits.
Larger extensions with prior approval
The larger home extension scheme lets you build a single storey rear extension of up to 6 m for attached houses and 8 m for detached houses. You notify the council, which consults your neighbours. If nobody objects, or the council decides the impact on neighbouring amenity is acceptable, you can proceed. The council has 42 days to decide.
Side extensions
A single storey side extension can be permitted development if it is no more than 4 m high and no wider than half the width of the original house. Side extensions are not permitted development in conservation areas and other designated land, and wrap-around extensions that combine rear and side usually need planning permission.
Two-storey extensions
A two-storey rear extension can be permitted development if it extends no more than 3 m beyond the original rear wall, is at least 7 m from the rear boundary, and upper floor side windows are obscure glazed and non-opening below 1.7 m. In practice, many two-storey designs need full planning permission, which typically takes 8 weeks to decide.
When permitted development does not apply
Flats and maisonettes, listed buildings, and houses where permitted development rights have been removed by a planning condition or an Article 4 direction all need planning permission. Conservation areas, National Parks and other designated land have tighter rules. Your council can confirm whether rights still apply to your house.
Building Regulations and party walls
Building Regulations approval is needed for every extension. It covers foundations, structure, drainage, insulation, glazing, ventilation and fire safety. If you build on a boundary wall or dig foundations near a neighbour's, the Party Wall etc. Act 1996 requires notice: one month for excavations, two months for work to a party wall.
Further reading
This guide is general information for England and is not a substitute for advice on your specific property. Planning rules differ in Wales, Scotland and Northern Ireland. Always confirm with your local planning authority.