Many single-storey and some two-storey extensions in England can be built without a full planning application, under permitted development rights. Knowing the limits before you design an extension can save months of waiting and a lot of money. Here is a plain-English overview of the main rules for houses.
Permitted development applies to houses, not flats
Permitted development rights for extensions apply to houses. Flats and maisonettes do not have them, and some houses have had them removed – by a planning condition on a newer estate, or by an Article 4 direction. Listed buildings always need consent. Check with your council if you are unsure.
Single-storey rear extensions
- Up to 3 metres deep from the original rear wall for an attached house (semi-detached or terraced).
- Up to 4 metres for a detached house.
- Maximum height 4 metres.
- If within 2 metres of a boundary, the eaves can be no higher than 3 metres.
The larger home extension scheme
Through a prior approval process with the council, single-storey rear extensions can go up to 6 metres (attached) or 8 metres (detached). Your neighbours are notified and can comment, and the council decides based on the impact on their amenity. It is quicker and simpler than a full planning application, but you must have the approval before you build.
Side extensions
- Single storey only, maximum height 4 metres.
- Width no more than half the width of the original house.
- Not allowed under permitted development on “designated land” such as conservation areas, National Parks and Areas of Outstanding Natural Beauty.
Two-storey rear extensions
- No more than 3 metres beyond the original rear wall.
- At least 7 metres from the rear boundary.
- Roof pitch to match the existing house as far as practical, and upper-floor side windows obscure-glazed and non-opening below 1.7 metres.
Rules that apply to every extension
- Extensions and other buildings must not cover more than half the land around the original house.
- Materials should be similar in appearance to the existing house.
- No extension forward of the principal elevation facing a road.
- “Original house” means as it was first built (or as it stood on 1 July 1948) – earlier extensions count towards the limits.
Permitted development is not the end of the paperwork
- Building Regulations approval is still required for an extension: structure, insulation, fire safety, drainage and ventilation.
- A Lawful Development Certificate from the council is optional but proves the extension was lawful – very useful when you sell.
- If you build on or near a shared wall or dig foundations close to a neighbour’s, the Party Wall etc. Act 1996 may require you to serve notice.
These are the main limits as they stood in 2026; the full conditions are on the government’s Planning Portal, and it is always worth checking before you commit.
Planning an extension?
We build new homes and extensions across the UK – from small single-storey additions to complete new builds – with one team from the first conversation to handover. Tell us about your project.
