Do I need planning permission for a rear extension?
A single storey extension at the back of a house is often permitted development in England, which means no planning application, as long as it stays within set limits. Here is what those limits are, when you do need permission, and what else to sort out.
Check your own single storey rear extension in about 20 seconds: we look up your postcode's official conservation area and Article 4 data and apply these rules to your home.
These are the rules for houses in England. Wales, Scotland and Northern Ireland have their own, similar but different. Flats and maisonettes have no householder permitted development rights.
Usually no planning permission needed if
- It goes no more than 3m beyond the original rear wall on an attached house (semi or terrace), or 4m on a detached house.
- It is no more than 4m high, and the eaves are no higher than 3m if it is within 2m of a boundary.
- With all other extensions and outbuildings, it covers no more than half the land around the original house.
- The materials look similar to the house.
- Up to 6m (attached) or 8m (detached) is possible through the prior approval scheme: you notify the council, neighbours are asked, and you wait for the council's answer before starting. Not available in conservation areas.
You need planning permission if
- It goes beyond those limits.
- Your home is a flat or maisonette: flats have no householder permitted development rights.
- Your home is listed: you need listed building consent for most work, inside or out.
- Your permitted development rights were removed by a planning condition or an Article 4 direction (ask the council, or check the planning history of your home).
- It includes a balcony, veranda or raised platform over 0.3m.
Building regulations
Yes. A rear extension needs building regulations approval (foundations, structure, insulation, drainage, fire safety), through your council's building control or an approved inspector, and a completion certificate at the end.
Planning permission and building regulations are separate: a project can need one, both or neither.
Also think about
- Party wall notice if you build on or near the boundary, or dig foundations close to a neighbour's.
- A Lawful Development Certificate from the council if you want proof it is permitted development (useful when you sell).
- Drains: building over or near a shared sewer usually needs the water company's agreement.
Questions people ask
Does the 3m rule start from my current back wall?
It starts from the original rear wall, meaning the house as first built (or as it stood on 1 July 1948). An earlier extension counts towards the limit.
Can I build a rear extension in a conservation area without permission?
A single storey rear extension within the standard limits can still be permitted development in a conservation area, but the larger prior approval route is not available, and some councils remove rights with an Article 4 direction. Check with the council first.
How do I get certainty?
Apply to your council for a Lawful Development Certificate for the proposed extension. It confirms the work is permitted development.
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General guidance from LocalWins, last checked October 2026. It is not legal advice or a planning decision, and every home is different: confirm anything important with your council or a qualified professional.