If, however, your garden building does comply with the above criteria, you won't need to apply for planning permission and you can have a garden building up to 30m2 (internal size). anything bigger than 30m2 will need to go through building regulations.. Home owners: outbuildings and structures. garden sheds, greenhouses and other buildings. planning permission is not required provided that: 1. the shed / greenhouse / building is used for domestic purposes only. 2. the ground area covered by the shed/greenhouse/building and any other buildings within the boundary of the property, excluding the. Planning permission is not required (permitted development) for a shed if you meet the following criteria.is located to the rear of the property (behind the front elevation or elevation that faces a road). it does not exceed 4 metres in height (3 metres to eaves)..