Two-storey (or higher) rear extensions have tighter limits than single-storey ones under Class A.
Maximum depth 3m beyond the rear wall of the original house - there is no Prior Approval route to go further, unlike single-storey extensions.
Must be more than 7m from the rear boundary.
Eaves and ridge height must not exceed the existing house, and materials must match.
Two-storey side extensions are not covered by Class A at all and need full planning permission.
England only. Takes about a minute.
Last reviewed 2026-09-01. Guidance, not legal advice.