Permitted development, explained honestly
England lets you extend and convert within fixed national limits without a planning application. Here are the numbers that matter, the exceptions that catch people out, and how to get certainty before you build.
The limits that matter
- Single-storey rear extension: 3 m deep (attached; semi-detached and terraced houses count as attached) or 4 m (fully detached), up to 4 m high; deeper (up to 6/8 m) via the prior approval route with neighbour consultation.
- Two-storey rear extension: at most 3 m beyond the rear wall and at least 7 m from the rear boundary.
- Side extension: single storey, at most half the width of the original house, 4 m high; not on designated land.
- Loft: 40 m3 extra roof volume for terraced houses, 50 m3 for semis and detached; no dormer on the front, nothing above the ridge.
The exceptions that catch people out
- Flats and maisonettes have no permitted development rights for extensions or dormers; planning permission is always needed.
- A listed building almost always needs listed building consent on top of planning permission, even for smaller works.
- On designated land (conservation area, AONB, national park, world heritage site) parts of permitted development fall away: no side extensions, no dormers, and stricter limits on the rest.
- An Article 4 direction can remove permitted development locally; your council can tell you whether one applies to your address.
Want the answer for your own project? The free planning permission check walks through these rules in at most seven questions, and this guide explains why building regulations still apply either way. Sources: Planning Portal (planningportal.co.uk) and the HomeOwners Alliance permitted development guide, checked 3 August 2026.
Frequently asked questions
Do permitted development rights ever run out?
No, but they can be used up: the loft volume allowance counts every roof enlargement ever made to the house, and extensions count against the original house as it stood in 1948 or when first built. A previous owner may have spent your allowance.
Can my council remove permitted development?
Yes, with an Article 4 direction, common in conservation areas. Your council can tell you in minutes whether one applies to your address, and it is exactly why written certainty via a Lawful Development Certificate is worth having.
Do these rules apply outside England?
No. Planning is devolved: Scotland, Wales and Northern Ireland each have their own versions with different limits. This page follows the English rules; planningportal.co.uk links the official guidance for each nation.