It is the first question almost everyone asks us. The honest answer is “it depends”, but it is usually possible to get a clear answer quite quickly once you know what to look for.
Permitted development
Most houses in England have permitted development rights. These let you build a single-storey rear extension without a full planning application, as long as you stay within certain limits. In general that means up to 3 metres deep on an attached house and up to 4 metres on a detached house, with a maximum height of 4 metres. The extension also has to use materials similar to the existing house and can’t cover more than half the garden.
There is also a prior approval route that allows bigger single-storey extensions, up to 6 metres on attached houses and 8 metres on detached ones. The council notifies your neighbours and has to decide within 42 days.
When you will need planning permission
You will normally need a full householder application if:
- the house is a flat or maisonette (these don’t have permitted development rights)
- the property is listed or in a conservation area
- the council has removed permitted development rights, either through an Article 4 direction or a condition on an earlier approval
- the extension is two storeys and close to a boundary, or goes beyond the size limits above
Get it in writing
Even if your extension is permitted development, it is worth applying for a Lawful Development Certificate. It is formal confirmation that the work didn’t need planning permission, and buyers’ solicitors will often ask for it when you sell.
Wales, Scotland and Northern Ireland have their own rules, which differ in the detail. If you are not sure where your project stands, get in touch and we will take a look.