Class A of The Town and Country Planning (General Permitted Development) (England) Order 2015 permits the erection of single-storey side and rear extensions, subject to limitations and conditions.
Some of the limitations are:
- Single storey rear extensions can extend up to 4 metres for a detached house, and 3 metres of any other house.
- Under prior approval notification, it can extend up to 8 metres for a detached house, and 6 metres of any other house.
- It can be extended up to 4 metres in height
- Side extensions can be extended up to half the width of the house.
Some of the conditions are:
- The materials used in the extension must be similar to the existing house.
- Any upper floor window of the side elevation must be obscured and non-opening below 1.7 metres of the floor of the room.
Please refer to this legislation.