If you want to develop within Permitted Development. You can have spare room(s) within Outbuilding used as Play area, Exercise area, Hobby room, Office or may be a Summer house, You can install a kitchen or bathroom in new outbuildings, but not both; if you do it will be classed as a self-contained dwelling and this will need a Planning Permission.
In most cases, Outbuildings are permitted development. By using the governments Permitted Development (PD) legislation, you can have outbuildings covering a maximum area of half of your garden area so long as it is within other strict Government guidelines, which will not require Planning Permission, unless you’re Permitted Development (PD) rights have been removed. For outbuildings over 30 square metres in area, you will also need Building Regulations approval, it could turn out to be a costly outbuilding.
