Garden rooms are permitted developments, which means they don’t require planning permission as long as they do not go over a certain size. They must be single storey buildings, and the height of the eaves must be a maximum of 2.5 metres. If it has a dual pitched roof, the maximum overall height must be no more than 4 metres. If not, the maximum height is 3 metres. However, if it is located within 2 metres of the boundary of your property, the maximum height is 2.5 metres. In addition, it must be under 10m x 10m in size.