Do you need planning permission for an extension?
Often not. Many house extensions in England are permitted development — you can build without a planning application, provided you stay inside a specific set of limits. Those limits are what this page is about.
The short answer
If your extension is single storey, at the rear, within the depth and height limits below, built in materials similar to the existing house, and your property is not a flat, a maisonette, a listed building or on designated land — it is very likely permitted development.
If any one of those is not true, assume you need a planning application until your council tells you otherwise.
Permitted development rights apply to houses, not flats or maisonettes. They are restricted or removed on designated land (conservation areas, National Parks, AONBs, World Heritage Sites), on listed buildings, and on some newer estates where the original planning permission removed them by condition. Checking that last one is worth ten minutes of your time before you spend anything.
Single-storey rear extensions
| Limit | Detached house | Semi-detached or terraced |
|---|---|---|
| Depth from the original rear wall | up to 4m | up to 3m |
| Depth via larger home extension prior approval | up to 8m | up to 6m |
| Maximum height | 4m overall | |
| Height within 2m of a boundary | eaves no higher than 3m | |
| Coverage | extensions must not cover more than half the land around the original house | |
“Original house” means the house as first built, or as it stood on 1 July 1948 — not as you bought it. A previous owner’s extension counts against your allowance.
Side extensions
Can be permitted development if single storey, no more than half the width of the original house, no more than 4m high, and not forward of the principal elevation. On designated land, side extensions are not permitted development at all.
Two-storey and multi-storey rear extensions
Tighter: no more than 3m deep, not within 7m of the rear boundary, roof pitch matching the existing house where practicable, and upper-floor side windows obscure-glazed and non-opening below 1.7m. Not permitted development on designated land.
Wraparound extensions
A wraparound combines a rear and a side extension. Each part may sit inside its own limits, but combined they usually do not — wraparounds commonly need a planning application. Ask the council before you commission drawings.
Permitted development is not the same as approval
- Planning permission is about whether you may build the thing at all — its size, siting and effect on neighbours and the street.
- Building Regulations are about whether it is built safely: structure, insulation, fire escape, drainage, ventilation. They apply to virtually every extension, including permitted development ones. See building regulations for extensions.
Worth getting: a Lawful Development Certificate
Build under permitted development and nobody issues you an approval — which is awkward years later when a buyer’s solicitor asks for evidence. A Lawful Development Certificate is the council confirming in writing that what you built did not need permission. It costs a fraction of a planning application. If you are building to the edge of the limits, get one.
Frequently asked
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