The most common question we get from homeowners planning a rear extension is: do I need planning permission? The answer depends on the size of the extension, your property type, and where you live. Here is a clear guide.
The good news: most single-storey rear extensions do not need planning permission
Under Permitted Development Rights, you can build a single-storey rear extension without a planning application, provided it meets specific conditions. For most houses in London, this means:
Attached (terraced or semi-detached) houses:
- Maximum depth: 3 metres beyond the original rear wall
- Maximum height: 4 metres (with a maximum eaves height of 3 metres)
Detached houses:
- Maximum depth: 4 metres beyond the original rear wall
- Maximum height: 4 metres
The Larger Home Extension Scheme (Prior Approval)
Since 2019, the Larger Home Extension Scheme has allowed deeper single-storey rear extensions under a process called Prior Approval:
- Attached houses: up to 6 metres depth
- Detached houses: up to 8 metres depth
This is not a full planning application. Your local council notifies your neighbours and has 42 days to decide. In the vast majority of cases, Prior Approval is granted. Many of the extensions we build in Newham, Barking, Redbridge, and Havering use this route.
When do you need full planning permission?
Your extension exceeds the depth limits above. Anything deeper than 6m (attached) or 8m (detached) at single-storey, or any two-storey rear extension, requires a full application.
You are in a conservation area or AONB. Conservation areas have additional restrictions. Rear extensions that are visible from a road or public space may require permission even at standard depths. Always check before assuming permitted development applies.
Your property is listed. Listed building consent is required for any alterations to a listed building, inside or out.
You want to extend to the side as well. Side extensions that project beyond the original side elevation often require planning permission, especially in designated areas.
Permitted development rights have been removed. Some properties — particularly on new-build estates — have had their permitted development rights removed by a planning condition on the original permission. Check your title deeds or contact your local planning authority.
You want a two-storey rear extension. Two-storey rear extensions always require full planning permission. They must also set back 7 metres from the rear boundary.
What about Article 4 Directions?
Several London boroughs have implemented Article 4 Directions that remove some or all permitted development rights in specific areas. These are most commonly used to control HMO conversions, but some also affect extensions. If you are in Newham, Waltham Forest, or Redbridge, it is worth checking whether an Article 4 Direction applies to your property. We check this on every project before advising you.
Do you need Building Regulations approval even if no planning is needed?
Yes, always. Planning permission and Building Regulations are two separate things. Almost all rear extensions require Building Regulations approval regardless of whether planning permission is needed. Building Control covers structural integrity, insulation, drainage, fire safety, and electrics. We manage the Building Control process as part of every project.
How long does it take to get permission?
- Permitted development (no application needed): you can start immediately once you have confirmed PD applies.
- Prior Approval (Larger Home Extension Scheme): 42 days from submission.
- Full planning application: 8 weeks for a standard householder application (though complex applications or busy periods can extend this).