Permitted development checker for rear extensions
Can your rear extension go ahead without planning permission?
Ready to get real prices?
Tell us about your project and up to three London planning consultants will get back to you with quotes. Free, with no obligation.
Many rear extensions can be built without a full planning application under permitted development rights. The rules are strict on depth, height and position, and a single detail such as a raised terrace can tip a project into needing permission.
Answer the questions and the checker tells you whether your extension is likely to be permitted development, needs prior approval through the larger home extension scheme, or needs full planning permission.
London has a lot of conservation areas and Article 4 directions, which remove some or all of these rights. Always check with your council, and consider a Lawful Development Certificate before you build.
Questions people ask
How far can I extend without planning permission?
A single storey rear extension can go 3 m deep on a terraced or semi detached house and 4 m on a detached house. Under prior approval this rises to 6 m and 8 m.
Do permitted development rights apply to flats?
No. Flats and maisonettes don't have householder permitted development rights, so an extension to a flat needs planning permission.
What is a Lawful Development Certificate?
It is a formal confirmation from the council that your project is lawful without planning permission. It is optional, but buyers and their solicitors often ask for one.
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