A bigger rear extension can give you room for a wider kitchen, a dining table, and a calm seating area facing the garden. Before you start sketching layouts, it helps to know which planning route your project may follow.
For many homes in England, a larger single-storey rear extension may be possible through prior approval rather than a full householder planning application. This route is still formal, but it is usually focused on a narrower set of questions.
What is Prior Approval?
Prior approval is a planning process linked to permitted development rights. Permitted development allows certain home improvements to go ahead without a full planning application, as long as the project stays within set limits.
A prior approval for a larger home extension application is used when a rear extension is deeper than the standard permitted development allowance, but still within the larger extension limits. The council checks the proposal and consults adjoining neighbours before work can begin.
This process only applies to larger single-storey rear extensions. It does not cover a two-storey extension, a side extension on its own, a loft conversion, or every type of wraparound extension.
How Big Can a Larger Rear Extension Be?
The key measurement is taken from the rear wall of the original house. In planning terms, the original house means the house as it was first built, or as it stood on 1 July 1948 if it was built before then. This can catch people out if a previous owner has already added to the property.
For a detached house, the larger home extension route can allow a single-storey rear extension of more than 4 metres and up to 8 metres from the original rear wall. For any other house, including semi-detached and terraced homes, it can allow more than 3 metres and up to 6 metres.
So, if you own a terraced house and want a 5-metre rear kitchen extension, the larger extension prior approval route may be relevant. If the same house only needs a 3-metre rear extension, it may sit within standard permitted development, subject to the usual checks.
What Conditions Do You Need to Follow?
Depth is only part of the picture. A larger rear extension must be single-storey and no more than 4 metres high. If any part of the extension is within 2 metres of the boundary, the eaves height is usually limited to 3 metres.
External materials should have a similar appearance to the existing house, unless the work is a conservatory. The project also cannot result in buildings covering more than half the land around the original house.
Permitted development rights can be limited or removed on some homes, including:
- Listed buildings
- Flats
- Maisonettes
- Newer homes
- Properties affected by planning conditions
- Homes in protected areas
Larger rear extensions are not available under this route on Article 2(3) land, which includes:
- Conservation areas
- National Parks
- The Broads
- World Heritage Sites
- Areas of Outstanding Natural Beauty
How Do You Apply for Prior Approval?
To apply, you submit a Prior Approval: Larger Home Extension application to your local planning authority, usually through the Planning Portal. The application needs enough information for the council to understand the proposal, including:
- A written description of the extension
- The depth from the original rear wall
- The height at the eaves and highest point
- A site plan showing the proposed work and any existing extension it will join
- Addresses for adjoining properties
- The applicant’s contact details
The prior approval for a larger home extension fee is currently listed as £249 in England. Fees can change, and there may be separate Planning Portal service charges, so check the current fee before submitting.
What Happens After You Submit?
Once the application is valid, the council contacts adjoining owners or occupiers, usually neighbours who share a boundary, including to the rear. The notice explains the proposal, gives the end date for the 42-day decision period, and tells neighbours how long they have to object. That objection period must be at least 21 days.
You cannot start work straight away. The extension can only go ahead once the council writes to confirm that prior approval is not required, grants prior approval after considering the impact on neighbours, or fails to issue a decision within the 42-day period.
What if Neighbours Object?
A neighbour’s objection does not automatically stop the project. It means the council must look at whether the extension would have an unacceptable effect on adjoining properties. In plain terms, this usually means light, outlook, privacy and how the extension would feel from next door.
The council is not re-running a full planning application. It is considering neighbour amenity within the prior approval extension process. If the council decides the impact is acceptable, the project can proceed. If approval is refused, there is a right of appeal.
It can help to speak to neighbours before the application is submitted. Clear drawings and a considered design can reduce surprises.
Don’t Forget Building Regulations
Planning and building regulations are separate. Even if your prior approval application is accepted, the extension still needs to meet building regulations. This covers structure, foundations, drainage, insulation, ventilation, fire safety and electrics. Permitted development rights also do not remove requirements under other regimes, including building regulations and the Party Wall Act.
Planning a Larger Home Extension with Plus Rooms
A prior approval for a larger home extension can be a useful route for creating more space, but only when the property, design and paperwork all fit the rules.
Plus Rooms offers an extension design and build service that brings design, planning and construction together in one coordinated process. From the first ideas through to applications, technical details and the build itself, the team can help you understand which route suits your home and what needs to happen next.
If you are thinking about a larger rear extension, contact us for advice on your options and the steps involved. You can also read the Plus Rooms guide to building regulations in the UK for more on the approvals that may sit alongside planning.
