Do I need planning permission for an extension, or is it permitted development?
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Short answer: many single-storey extensions do not need a planning application, because permitted development rights already grant permission within set limits. Stay within those limits and you can build after confirming the position with your council, ideally through a lawful development certificate. Go beyond them, live in a flat, or live in a conservation area with restrictions, and you need a householder planning application. We check which side of the line your project sits at the free consultation, and handle the paperwork either way.
The permitted development limits that matter most
For houses in England, the headline limits published by the government's Planning Portal are:
- A single-storey rear extension can extend up to 4 metres beyond the original rear wall for a detached house, or 3 metres for any other house.
- Under the larger home extension scheme those depths rise to 8 metres and 6 metres, but only after a prior approval process where neighbours are consulted.
- Single-storey rear extensions cannot exceed 4 metres in height.
- Side extensions must be single storey and no more than half the width of the original house.
- Extensions of more than one storey must not extend more than 3 metres beyond the original rear wall, among other conditions.
- These rights apply to houses only, not flats or maisonettes.
"Original" means the house as first built or as it stood on 1 July 1948. Previous extensions use up the allowance, which catches many people out.
Get it in writing. Permitted development is a legal position, not a feeling. A lawful development certificate from your council confirms your extension is lawful before you build, and makes life easier when you sell. We prepare the application as part of the design stage.
Not sure which side of the line your project sits? We check at the free consultation, with no obligation.
Book a Free ConsultationWhen you definitely need an application
- You want to go beyond the limits above, or extend forward of the principal elevation
- The property is a flat or maisonette
- You are in a conservation area or other designated land where rights are reduced, or an Article 4 direction removes them
- The house is listed, where listed building consent has its own regime
A householder application is not a disaster; it is a process. The statutory target for deciding most householder applications is 8 weeks (gov.uk guidance on determining applications), and good design that respects neighbours usually passes.
When this is not what you want to hear
If the plan depends on maximum size in a conservation area, or the house has already used its permitted development allowance, the honest advice may be a smaller scheme or a full application with a real refusal risk. We tell you that at the consultation stage, before you have spent money on ambitions the council will not approve. Planning is also separate from building regulations, which apply either way; see our guide to building regulations for homeowners.
Quick answers
Do I need planning permission for a rear extension?
Often not. Single-storey rear extensions up to 4 metres deep on a detached house, or 3 metres on any other house, usually fall within permitted development for houses in England, subject to height and other limits. Flats do not have these rights. Confirm the position with a lawful development certificate before building.
What is the larger home extension scheme?
A prior approval process that can allow single-storey rear extensions up to 8 metres on detached houses or 6 metres on other houses. The council consults your neighbours before it is confirmed, and conditions still apply.
How long does a householder planning application take?
The statutory target for deciding most householder applications is 8 weeks from validation, per government guidance. Complex cases and extensions of time can lengthen that.
Next step: a free consultation on your actual project, or browse the rest of the advice hub.