Do I need planning permission for a garden room?

Usually not, if your garden room is built under permitted development rights and stays within the size and height limits. The main restrictions are 2.5m maximum overall height within 2m of a boundary, 4m for a dual pitched roof or 3m for any other roof elsewhere, nothing forward of the principal elevation of the main house, and no more than half the land around the original house covered. Listed buildings always need planning permission, while flats and maisonettes do not benefit from permitted development. If you’re planning your garden room, it’s worth checking the rules before you build.