Guide · 15 October 2026

Do you need planning permission for a house extension?

Plenty of single-storey extensions in England can be built without a planning application, under what are called permitted development rights. Whether yours qualifies depends on the type of house, its location and what has already been added to it.

The headline limits

According to the Planning Portal's guidance for houses (not flats or maisonettes):

• A single-storey rear extension can usually go out up to 3 metres from the original rear wall, or 4 metres for a detached house.
• Under the "prior approval" route, those limits rise to 6 metres and 8 metres, but you must notify the council first and neighbours can comment.
• Extensions and other buildings cannot cover more than half the land around the original house.
• Within two metres of a boundary, the eaves cannot be higher than three metres.
• Side extensions can only be single storey, no more than four metres high and up to half the width of the original house.
• Materials should look similar to the existing house.

When the rules don't apply

Permitted development doesn't cover flats and maisonettes, and it is restricted on "designated land" such as conservation areas. Many London councils also use Article 4 directions that remove some rights on particular streets. If any of these apply, you'll need a householder planning application.

Our advice

Even if you think the work is permitted development, a Lawful Development Certificate from the council gives you written proof, which is useful when you sell. Building Regulations approval is a separate matter and is needed either way.

Sources: Planning Portal – Extensions; GOV.UK – Planning permission. Rules can change, so always check the current guidance and your council's website before you start.