Main limits for houses
| Project | Main permitted development limits |
|---|---|
| Single-storey rear extension | Up to 3 m deep (4 m detached), or 6 m / 8 m with prior approval; max 4 m high; eaves max 3 m within 2 m of a boundary |
| Side extension | Single storey; max 4 m high; no wider than half the original house; not on designated land |
| Two-storey rear extension | Max 3 m deep; at least 7 m from the rear boundary; matching roof pitch; obscure-glazed side windows |
| Porch | Max 3 m² floor area; max 3 m high; not within 2 m of a boundary with a road |
| Loft conversion | Up to 40 m³ (terraced) or 50 m³ (semi / detached); not beyond the front roof slope facing a road; not above the ridge |
| All extensions | Together with outbuildings, no more than 50% of the land around the original house; materials similar in appearance |
Designated land
In conservation areas, National Landscapes (such as the Chilterns), National Parks and World Heritage Sites, permitted development is reduced: no side extensions, no cladding, rear extensions limited to one storey, and no loft conversions under permitted development.
Article 4 directions
Councils can remove some permitted development rights in specific areas using Article 4 directions. We check your address before any design work.
This guide summarises rules for houses in England at the time of writing and is for guidance only. Rules differ for flats, listed buildings and designated land, and can be changed by Article 4 directions. Always check the Planning Portal or ask us — we confirm the route for your home before design starts.