Do I need planning permission for a rear extension?

Permitted development, prior approval, conservation areas and listed buildings: what applies to your house, in plain English.

Ruth Mortise

Director & project manager

The back of a brick terrace house with drawings on a garden table, ready to plan an extension

Many single-storey rear extensions can be built under permitted development, without a full planning application. But the rules change in a conservation area, and they don’t apply at all to listed buildings or flats.

As a rough guide, a detached house can extend up to 4 metres at the back and a terraced or semi-detached house up to 3 metres, no higher than 4 metres. Larger extensions can still go ahead through the prior approval scheme, where neighbours are asked for comments.

In Lewes, much of the town is a conservation area, so side extensions and changes to the front almost always need permission. We always check the planning history of the house before we draw anything.

Whatever the planning route, you will still need building control approval, and often a party wall agreement. We handle all three as part of the job.

N° 01 — Keep reading