Larger home extension prior approval is a permitted development route for certain single-storey rear extensions.
It applies where the proposed extension is deeper than the standard permitted development limits, but still within the larger home extension allowance.
The Planning Portal explains that prior approval for larger home extensions applies to single-storey rear extensions extending beyond the rear wall of the original house by over 3 metres and up to 6 metres for all houses other than detached houses, and over 4 metres and up to 8 metres for detached houses.
This is not the same as a full planning application. However, the council must be notified and adjoining neighbours are consulted.
If no relevant objections are received, the proposal may proceed under the prior approval process. If objections are received, the council will assess the impact on neighbouring amenity before deciding whether prior approval should be granted.
Extend Further Under The Larger Home Extension Prior Approval Route
Some single-storey rear extensions can go beyond the usual permitted development depth limits by using the larger home extension prior approval process.
This route can allow rear extensions of up to 6 metres for terraced and semi-detached houses, and up to 8 metres for detached houses, subject to the rules and neighbour consultation.
At Detailed Planning, we check whether your property is suitable, prepare accurate drawings following a point cloud scan where required, submit the prior approval application and advise on the planning risks before you commit to the build.
This can be a useful route for homeowners who want a deeper single-storey rear extension without making a full householder planning application.
Our Larger Home Extension Prior Approval Services
We provide prior approval application services for larger single-storey rear extensions across London and surrounding areas.
Property Suitability Check
We first check whether the property is likely to qualify.
Larger home extension prior approval is not suitable for flats, maisonettes, two-storey extensions, side extensions or properties where the relevant permitted development rights do not apply.
Planning History Review
We review the property’s planning history to understand previous extensions, planning conditions and whether permitted development rights may have been removed.
Previous extensions can affect whether the proposal stays within the permitted depth limits.
Point Cloud Survey And Existing Drawings
Where required, we visit the property and carry out a point cloud scan to prepare accurate existing drawings.
This helps reduce the risk of submitting drawings based on inaccurate dimensions or assumptions.
Proposed Extension Drawings
We prepare clear proposed drawings showing the extension depth, height, eaves height, roof form, relationship to boundaries and relationship to neighbouring properties.
This is especially important where the proposal is close to the maximum depth.
Prior Approval Submission
We prepare and submit the prior approval application to the council.
The application will usually include the required drawings, application form, description of the proposed extension and supporting information.
Advice After Neighbour Consultation
If neighbours object, we advise on the likely risk and whether amendments or a new application may be needed.
This may include reducing the depth, lowering the height, changing the roof form or considering a full householder planning application instead.
Projects That May Suit Larger Home Extension Prior Approval
Larger home extension prior approval is a specific route. It is not suitable for every extension.
Larger home extension prior approval can be a useful route, but it needs accurate drawings, careful neighbour risk advice and a clear understanding of the rules.
Planning Route Advice Before You Commit
We check whether prior approval is the right route before preparing the application.
If the property is not suitable, we will explain why and advise on alternative planning options.
Accurate Point Cloud Surveys
Where required, we use point cloud scanning to prepare accurate existing drawings.
This is particularly important where the extension depth, eaves height and relationship to boundaries need to be shown clearly.
Practical Design Advice
We consider not just the maximum possible depth, but also whether the design is likely to be acceptable to neighbours and the council.
Neighbour Risk Considered Early
We help identify where objections may be likely and advise on design adjustments that could reduce the risk.
Clear Prior Approval Submission
We prepare the drawings, forms and supporting information needed for the council to assess the application.
Support After Decision
If the application is approved, we can assist with building regulations drawings and the technical stage. If it is refused, we can advise on redesign, resubmission or alternative planning routes.
When Larger Home Extension Prior Approval May Not Work ⚠️
Larger home extension prior approval is not automatic.
It may not be suitable if:
The property is a flat or maisonette
The proposal is for a side extension
The proposal is for a two-storey extension
The property is in a conservation area or other excluded designated land
Permitted development rights have been removed
Previous extensions already use up the permitted depth
The extension would have an excessive impact on neighbours
The proposal has an eaves height above 3 metres
The extension would exceed 4 metres in overall height
Neighbours are likely to object and the impact is difficult to justify
The government’s householder guidance confirms that larger single-storey rear extensions under this route must not extend beyond 6 metres for any house other than a detached house, or 8 metres for a detached house, and the total height must not be more than 4 metres. It also explains that this route is subject to a neighbour consultation scheme.
We start by reviewing the property, proposal and planning history.
We check whether the house is likely to qualify for the larger home extension prior approval route and whether there are obvious risks, such as conservation area constraints, previous extensions, removed permitted development rights or likely neighbour impact.
We will also advise if another route, such as standard permitted development, Lawful Development Certificate or full householder planning application, may be more suitable.
2. Site Visit, Point Cloud Scan And Drawings
Where required, we visit the property and carry out a point cloud scan to prepare accurate existing drawings.
We then prepare the proposed drawings showing the extension depth, eaves height, maximum height, roof form and relationship to boundaries.
Accurate drawings are important because the application depends on compliance with specific size and height limits.
3. Prior Approval Application And Neighbour Consultation
Once the drawings are agreed, we prepare and submit the prior approval application to the council.
The council will notify adjoining neighbours. If no objections are received, the process is usually more straightforward.
If objections are received, the council will assess the impact on neighbouring amenity before deciding whether prior approval should be granted.
4. Decision And Next Steps
If prior approval is granted, the next stage is usually building regulations drawings, structural calculations and building control approval before works start.
If prior approval is refused, we can advise on the next step. This may include reducing the depth, lowering the height, changing the roof form, resubmitting the application or considering a full householder planning application.
Once prior approval is granted, the project is not automatically ready to build.
Most larger home extensions still need building regulations drawings, structural calculations, building control approval and possibly party wall matters before works begin.
The builder will need clear technical drawings showing construction details, insulation, drainage, structure, ventilation and fire safety requirements.
We can assist with the next stage by preparing building regulations drawings, coordinating with structural engineers and helping move the project towards construction.
If you are considering a 6 metre or 8 metre rear extension, we can check whether your property may qualify under the larger home extension prior approval route.
Send us the address, a short description of the proposal and any drawings or estate agent plans you already have.
We will review the project and advise on the most suitable next step.
Larger home extension prior approval is a permitted development process for certain single-storey rear extensions that go beyond the standard rear extension depth limits.
It allows the council to notify adjoining neighbours and decide whether prior approval is needed based on the impact on neighbouring amenity.
For terraced and semi-detached houses, the extension can be over 3 metres and up to 6 metres beyond the rear wall of the original house.
For detached houses, it can be over 4 metres and up to 8 metres beyond the rear wall of the original house.
The Planning Portal confirms that the prior approval process applies to larger single-storey rear extensions over 3 metres and up to 6 metres for all non-detached houses, and over 4 metres and up to 8 metres for detached houses.
A terraced house may qualify for a rear extension of up to 6 metres under the larger home extension prior approval route, provided the proposal meets the rules and the neighbour consultation process is satisfied.
Neighbour impact is especially important on terraced houses because properties are usually closer together.
Not quite. The larger home extension prior approval route only applies to rear extensions but if it is to the rear and touches a side wall, it must be half the width of the original house.
Side only extensions, wraparound extensions and two-storey extensions are not covered by this specific process.
For larger home extensions under this route, the total height must not exceed 4 metres.
The eaves height is also important, particularly where the extension is close to a boundary. As a general rule, the eaves height should not exceed 3 metres where relevant to the permitted development limits.
Neighbour consultation is a key part of the larger home extension prior approval process.
The council will notify adjoining neighbours. If objections are received, the council will assess the impact on neighbouring amenity before deciding whether prior approval should be granted.
It may be sensible to adjust the design before submission.
Options can include reducing the depth, lowering the eaves height, changing the roof form, using a pitched roof or setting bulk away from the boundary.
Sometimes a slightly smaller extension has a much better chance of approval.
If prior approval is refused, we can review the reasons and advise on the next step.
This may include revising the design, reducing the depth, lowering the height, changing the roof form, resubmitting the application or considering a full householder planning application.
Yes. Prior approval is a planning process. It does not replace building regulations.
Once prior approval is granted, most extensions still need building regulations drawings, structural calculations and building control approval before work starts.
Accurate drawings are important because the application depends on specific measurements, including extension depth, eaves height, maximum height and relationship to the original house.
A point cloud scan helps us prepare more reliable existing drawings before the proposed extension is developed.
The council process is usually shorter than many full planning applications, but timescales still depend on validation, neighbour consultation and council workload, typically they take 6 weeks following submission.
The application must go through the neighbour consultation process, and the council will issue a decision or confirmation of whether prior approval is required.
For larger home extension applications, the decision notice may say “Prior Approval Not Required” rather than “approved”.
This is usually a positive outcome. It means the council has confirmed that prior approval is not required and the extension can proceed under the larger home extension permitted development route, provided the works are built exactly as shown and comply with the relevant rules.
Yes. If the council refuses a larger home extension prior approval application, you can usually appeal the decision.
Before appealing, it is worth reviewing the refusal reasons carefully. In some cases, it may be quicker and more cost-effective to amend the design and resubmit, especially if the council’s concerns relate to depth, height, roof form or neighbour impact.
A Lawful Development Certificate is not usually compulsory after prior approval, but it can be recommended.
Prior approval deals with the neighbour consultation element of the larger home extension process. A Lawful Development Certificate can provide additional written confirmation that the works are lawful under permitted development, based on the full set of relevant rules.
This can be helpful for future sale, remortgage, solicitor enquiries or if questions are raised later.
