Answer the questions below for a single storey rear extension and see whether it is likely to fall under permitted development in England, or whether a planning application looks necessary. This is a guide, not formal confirmation.
Is the property a house? Flats, maisonettes and converted buildings do not have these rights.
Is it in a conservation area, AONB, national park, or is it a listed building? Designated land restricts permitted development.
Have the home’s permitted development rights been removed? An Article 4 direction or a planning condition can remove them. If unsure, choose No.
House type
How far will it project from the rear wall? In metres.
Height at the highest point? In metres.
Will any part be within 2 metres of a boundary? If yes, the eaves height must be no more than 3 metres.
Will more than half the land around the original house be covered by buildings after this? Includes sheds and previous extensions. If unsure, choose No.
Will it extend beyond a wall that faces a road? Usually the front, sometimes a side on a corner plot.
Single storey rear extensions in England can often be built under permitted development without a full planning application, provided they stay inside set limits. This tool checks the main ones:
Important. This is general guidance for England and a single storey rear extension only. It does not cover side or wraparound extensions, flats, designated land in full detail, or local rules. Permitted development is not the same as building regulations, which apply either way. The only way to be certain is a Lawful Development Certificate or written advice from your local planning authority. We are happy to help you check before you build.
