In short
- Many single-storey rear extensions fall under permitted development, within strict size and height limits.
- Listed buildings, flats and some newer estates don’t have the same rights.
- Building Regulations approval is needed either way.
- A Lawful Development Certificate gives you written confirmation before you build.
What is permitted development?
Permitted development rights let you carry out certain types of work without applying for planning permission. For houses in England, they cover many modest single-storey rear extensions, as long as the design stays within a set of limits on size, height and position.
They apply to houses only — not flats or maisonettes — and they can be removed or restricted in some areas, so it’s always worth checking before you rely on them.
The key limits for a single-storey rear extension
- Depth: up to 3 metres beyond the original rear wall for an attached house, or 4 metres for a detached house.
- Height: no more than 4 metres high, and no more than 3 metres at the eaves if the extension is within 2 metres of a boundary.
- Coverage: extensions and outbuildings together can’t cover more than half the land around the original house.
- Materials: the outside should look similar to the existing house.
- Position: extensions can’t project beyond the front of the house where it faces a road.
‘Original house’ means the house as it was first built — or as it stood on 1 July 1948 if it’s older — so extensions added by previous owners count towards your limits.
Thinking bigger?
Under the larger home extension scheme, single-storey rear extensions of up to 6 metres (attached) or 8 metres (detached) may be possible. You’ll need to notify your council first, and neighbours get the chance to comment before the council decides.
When you will need planning permission
- Two-storey extensions that don’t meet the stricter limits for extensions of more than one storey.
- Most side extensions wider than half the width of the original house.
- Listed buildings, which also need listed building consent for most alterations.
- Conservation areas, where side extensions and some types of cladding need permission.
- Homes where permitted development rights have been removed — common on newer estates, and in areas covered by an Article 4 direction.
Permitted development is about planning, not construction. Every extension still needs Building Regulations approval.
Don’t forget Building Regulations
Even if you don’t need planning permission, your extension must meet Building Regulations — covering structure, foundations, insulation, fire safety, drainage and ventilation. Building Control inspects the work at key stages and issues a completion certificate at the end, which you’ll need when you come to sell.
Get it in writing
If your extension falls within permitted development, you can apply to your council for a Lawful Development Certificate. It isn’t compulsory, but it confirms the work is lawful — and buyers’ solicitors often ask for one.
Every home is different, so always check with your local planning authority before you start. We’re happy to talk it through at your free survey and point you in the right direction.
Common questions
How long does a planning decision take?
Councils aim to decide householder planning applications within eight weeks of the application being validated. Notifications under the larger home extension scheme are decided within 42 days.
Do I need to tell my neighbours?
For a planning application or a larger home extension notification, the council notifies neighbours. If you’re building on or near a shared boundary, the Party Wall etc. Act 1996 may also require you to serve notice on them.
Can you help with planning?
Yes. We work alongside architects and designers, and can recommend local professionals to prepare your drawings and applications.
Written by MoreSpace Construction
A local building company based in Holbeach, with an office in Peterborough and over 10 years of experience in extensions, renovations, new builds and outdoor projects.
On this page
Share this article
Planning an extension?
Get a free, no-obligation visit and written quote from our local team.
