Rear Extension Planning Permission
Before you commit to drawings or a build date for your rear extension, you need to know whether it can go ahead under permitted development, needs the “larger home extension” prior approval route, or requires a full householder planning application.
This page explains how rear extension planning rules work in England, how much depth is usually allowed without full permission, and why properties in conservation areas or with removed rights need extra checks first.
Do you always need planning permission for a rear extension?
No. Many rear extensions can be built without a full planning application because they qualify under permitted development rights, but that depends on depth, height, plot type, and whether local restrictions or previous decisions have removed those rights.
Permitted development route
Under national permitted development rules, most houses (not flats or maisonettes) can add a single-storey rear extension up to a certain depth, height, and width without full planning permission, as long as other conditions are met.
- Applies to houses, not flats or maisonettes.
- Depth usually up to 3m for attached and 4m for detached houses as standard.
- Height and boundary rules must still be satisfied.
- Cannot exceed 50% of the original curtilage when combined with other outbuildings.
When full planning permission is needed
A rear extension generally needs a householder planning application where it breaches permitted development limits, is on designated land, or where rights have been removed by a previous decision or Article 4 direction.
- Depth beyond the permitted development limit without using the larger home extension route.
- Two-storey rear extensions or those close to boundaries.
- Flats, maisonettes, and some converted houses.
- Properties in certain conservation areas or under Article 4 restrictions.
Rear depth, height, and width rules
If you stay inside the main permitted development limits, you often avoid full planning permission. Going beyond them changes the route and usually the risk profile of the project.
Standard rear depth limits
Planning Portal guidance for England states that single-storey rear extensions on houses can normally extend:
- Up to 3 metres beyond the original rear wall for semi-detached, terraced, and other attached houses.
- Up to 4 metres beyond the original rear wall for detached houses.
Larger home extension route
Government guidance on larger home extensions notes that, subject to prior approval, those depth limits can increase to:
- Up to 6 metres for attached houses.
- Up to 8 metres for detached houses, outside Article 2(3) designated land.
This route still requires you to notify the local authority and follow neighbour consultation procedures.
Height and width considerations
Permitted development rules also control height and position:
- Maximum eaves and overall height relative to the existing house.
- Side extensions must not be wider than half the original house and may need separate checks.
- No building beyond the rear boundary or over set heights near boundaries.
Conservation areas and Article 4 directions
Many homeowners assume that permitted development applies everywhere, but local designations and previous decisions can remove or restrict those rights. Checking the planning history and local policy is essential before you rely on PD alone.
Conservation areas and designated land
National guidance describes “Article 2(3) designated land” including conservation areas, national parks, and some other protected locations. On this land, rear extension rights are more tightly controlled, especially for larger schemes or those near boundaries.
Local authorities also publish lists of conservation areas and local designations, which should be checked against your property address before you rely on the standard PD rules.
Article 4 directions and removed rights
Councils can issue Article 4 directions to remove specific permitted development rights in defined streets or areas. Where rights have been removed, you cannot rely on PD and must apply for planning permission instead.
Conditions attached to earlier planning decisions, or the cumulative impact of multiple extensions, can also restrict what you can build at the rear without a new application.
Three main planning routes for rear extensions
Rear extension projects usually take one of three planning paths. Choosing the right one at the start saves time, cost, and revision later on.
Permitted development (no full planning application)
If your rear extension meets the permitted development limits and conditions, you may be able to proceed without a full householder planning application. Many homeowners still apply for a Lawful Development Certificate to get written confirmation that the project is lawful.
Larger home extension prior approval
For deeper single-storey rear extensions, national guidance describes a “larger home extension” route, where neighbours are notified and the local authority assesses the impact on amenity. You do not submit a standard householder application, but you must follow the prior approval process and depth limits for your property type.
Householder planning application
Where the scheme does not qualify under PD or the larger home extension route, or where rights have been removed, a full householder planning application is required. Guidance lists a standard householder planning fee of £548, plus drawing, structural, and potential consultancy costs.
Rear extension planning permission FAQs
Do I always need planning permission for a rear extension?
No. Planning Portal and national guidance explain that many single-storey rear extensions on houses can be built under permitted development, as long as limits on size, height, and position are met and no local restrictions remove those rights.
How far can I extend without full planning permission?
In many cases, up to 3 metres beyond the original rear wall on attached houses and up to 4 metres on detached houses under standard permitted development, with the possibility of up to 6 metres and 8 metres respectively under the larger home extension prior approval route.
What if my home is in a conservation area?
Designated land such as conservation areas can have stricter rules and may limit permitted development rights. Councils can also issue Article 4 directions which remove specific PD rights, meaning a rear extension would need full planning permission rather than relying on the standard limits.
How much does a householder planning application cost?
Current guidance for England lists a standard householder planning application fee of £548, with additional professional and drawing costs depending on the complexity of your rear extension.
Should I still get a Lawful Development Certificate if PD applies?
Many homeowners choose to secure a Lawful Development Certificate even when the project appears to fall within permitted development. Guidance notes that this gives formal confirmation the extension is lawful, which can be helpful for future sales or mortgage purposes.
Not sure which planning route your rear extension should take?
Share a few details about your house and the extension you have in mind. We will advise whether permitted development, prior approval, or a full householder application is likely to be the right path for your project.