Jan 17, 2026
Thinking about a bigger single-storey rear extension? You might not need full planning permission. The government brought in a simpler route called prior approval, letting you build extensions larger than usual.
This process can save a lot of hassle—less paperwork, less cost, and usually less waiting around.
Prior approval lets you build single-storey rear extensions up to 8 metres deep on detached houses and up to 6 metres on semis or terraces. That's bigger than the usual limits—4 metres for detached, 3 metres for others.
Your local council will check with your neighbours about your plans. If nobody objects, or if the council's happy with your proposal, you can get going.
Understanding how prior approval works is a must before you start sketching ideas. The rules are pretty strict on size and design, and you'll need the right paperwork.
Honestly, if you get it wrong, you could face delays or even a flat-out "no," so it's worth getting clued up early.
Key Takeaways
Prior approval lets you build larger single-storey rear extensions without full planning permission if you meet size and design rules.
The council always asks your neighbours for feedback, and their objections can influence the decision.
You need to apply and wait for a decision before you start building.
What Is Prior Approval for Larger Rear Extensions?
Prior approval is a shortcut in the planning world. It lets you build a bigger single-storey rear extension without a full planning application.
It works under permitted development rights. These rights mean homeowners can make certain changes to their homes without the usual planning headaches.
Key Differences Between Prior Approval and Planning Permission
Prior approval and planning permission aren't the same. Prior approval is quicker and only checks specific things—mainly, how your extension affects your neighbours.
The council looks at whether your build would ruin your neighbours' enjoyment of their homes. They don't care about what materials you use or if the design matches your house.
Planning permission, on the other hand, digs into everything. The council checks the design, materials, and how your extension fits the area. It's slower and costs more.
Key differences:
Assessment scope: Prior approval checks neighbour impact; planning permission checks everything.
Processing time: Prior approval usually takes 42 days; planning permission can drag on for 8 weeks or more.
Cost: Prior approval is cheaper.
Consultation: Prior approval only involves immediate neighbours; planning permission might involve more people.
Permitted Development Rights and the Legal Framework
Permitted development rights come from Class A, Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015.
This law lets you build single-storey rear extensions up to certain sizes without planning permission. For permitted development, you get 3 metres for attached houses, 4 metres for detached.
Prior approval stretches these limits: 3 to 6 metres for semis and terraces, 4 to 8 metres for detached houses.
Extensions must be single-storey. The max height is 4 metres, and you can't build forward of your main front wall.
Size Limits and Types of Larger Rear Extensions
The rules for larger rear extensions depend on your house type. Detached homes can go up to 8 metres; others are capped at 6 metres.
These rules only apply if you're going beyond the standard permitted development limits.
Single-Storey Rear Extension Allowances
You measure a larger single-storey rear extension from the rear wall of your original house. "Original" means as first built, or as it stood on 1 July 1948 if it's older.
Under the prior approval process, you can go past the usual limits. Normally, it's 4 metres for detached, 3 metres for everything else. The larger extension scheme doubles that.
Your extension can't go over 4 metres in height. Anything taller means you'll need full planning permission.
Detached, Semi-Detached and Terraced Houses
Detached houses can extend between 4 and 8 metres from the original rear wall. That's an extra 4 metres over standard rules.
Semis and terraces can go between 3 and 6 metres. The rules don't fuss over whether you're end-of-terrace or in the middle.
Flats and maisonettes can't use prior approval for larger extensions. They're completely left out of this scheme.
Side Extensions and Larger Home Extensions
Side extensions have their own restrictions. Your rear extension can't stick out past a side wall by more than half the width of your original house.
This stops extensions from overwhelming the original property. Even if you stay within depth limits, the width rule still applies.
Two-storey extensions aren't allowed under prior approval. If you want to build up, you'll need full planning permission. The scheme is strictly for single-storey builds within your garden.
Eligibility Criteria and Exclusions
Not every property can use the larger home extension scheme. Some areas have extra rules or bans.
Properties Ineligible for the Larger Home Extension Scheme
Flats and maisonettes can't use this scheme—only houses are eligible.
If your home is listed, you're out of luck here too. Listed building status means a full planning application is required.
The extension must be single-storey and at the back of your house. Side and multi-storey extensions don't qualify. You also can't cover more than half the land around your original house.
The max height is 4 metres. If you build within 2 metres of a boundary, the height drops to 3 metres. Materials must match or at least complement your current home.
Restricted Areas and Article 4 Directions
If you live in a conservation area, Area of Outstanding Natural Beauty, or a Site of Special Scientific Interest, you generally can't use the larger home extension scheme. National Parks and the Broads have the same restrictions.
Your local planning authority can also issue an article 4 direction to remove permitted development rights in certain areas. This means you'll need full planning permission, even if your plans fit the usual criteria.
It's a good idea to check with your local authority before you do anything. They'll tell you if any extra restrictions or article 4 directions apply.
Key Conditions and Design Requirements
Your extension has to meet strict size and design standards for prior approval. It must be single-storey, and there are firm rules about materials and use.
Height, Depth, and Boundary Limits
The extension can't be taller than 4 metres from the ground. Eaves must stay under 3 metres. If you're building within 2 metres of a boundary, the whole extension can't be more than 3 metres high.
For depth, detached houses get 4 to 8 metres; others get 3 to 6 metres, measured from the original rear wall. "Original" means as first built or as it was in July 1948.
You can't extend past the side walls of the original house. No upper floors or rooms in the roof—just single-storey. You'll need solid floor plans with exact measurements when you apply through the Planning Portal.
Materials, Appearance, and Usage Restrictions
Materials must match or at least complement your existing house. No wild colour or texture changes.
You can't use your extension as a separate home or for business. If your extension affects a shared wall, you'll need a party wall agreement before you start.
The design also has to meet building regulations—things like fire safety, structure, and insulation. That's a separate application from prior approval.
Understanding the Prior Approval Process
Applying for prior approval means submitting a formal application to your local council. They'll then consult your neighbours before making a decision.
The process has strict timelines and works differently from standard planning permission.
Neighbour Consultation Scheme Explained
Once you apply, the council must tell all adjoining neighbours about your proposed extension. They send a notice to anyone sharing a boundary.
Neighbours get 21 days to comment or object. The neighbour consultation gives people next door a chance to weigh in.
The council only considers objections about impact on amenity—like loss of light or feeling boxed in. Complaints about property values or personal issues aren't relevant.
Steps from Application to Decision
You need to send your prior approval application to the council, including:
A written description of your extension
How far it extends from the rear wall
Plans showing size and design
Any extra info the council asks for
The council gets 42 days to decide. The first 21 days are for neighbour consultation. After that, the council reviews responses and decides if the impact on neighbours is acceptable.
What Happens if Neighbours Object?
If neighbours object, the council checks if your extension harms their enjoyment of their property.
They can only refuse if the impact is clearly unacceptable. The focus is on amenity, not design or looks.
If nobody objects, things usually move faster.
It's smart to chat with your neighbours before applying. That way, you might head off objections early.
Deemed Consent and Approval Timescales
The council has to decide within 42 days. If they don't, you get deemed consent—automatic approval.
Still, it's wise to get written confirmation before you start building.
You've got three years from approval to begin work. If you don't start in time, you'll need to reapply.
Applying for Prior Approval: What You Need
The prior approval process needs specific documents and a formal submission to your local council.
You'll want to gather everything and use the right channels to avoid headaches.
Documents and Drawings Required
Your application must include a completed form, which you can get from your council's website or the Planning Portal.
You'll need these drawings:
Site location plan (your property outlined in red, scale 1:1250 or 1:2500)
Existing and proposed floor plans (scale 1:50 or 1:100)
Existing and proposed elevations (showing all sides)
Block plan (scale 1:500 or 1:200, showing the extension's position relative to boundaries)
Make sure all drawings have clear, accurate dimensions. Label how far the extension projects from the original house.
Remember—PlanSure helps homeowners decide early whether PD or full planning is the safer route.
Submitting Your Prior Approval Application
You can submit your prior approval application online through the Planning Portal or directly to your local planning authority.
Most councils prefer online submissions since they're usually processed faster.
The application fee varies by council, but you'll generally pay between £100 and £200.
Check your local authority's website for the exact fee before you apply.
Once you submit, the council gets 42 days to make a decision.
During this time, they'll notify your adjoining neighbours about your plans.
Your neighbours have 21 days to raise concerns about the extension's impact on their property.
If you don't hear back within 42 days, prior approval is automatically granted.
Still, it's smart to get written confirmation from the council before starting work—just to avoid any headaches.
After Approval: Next Steps and Compliance
Once you receive prior approval for your larger rear extension, you still need to meet building regulations.
It's also wise to consider getting formal documentation of your lawful development.
These steps make sure your extension is sound, safe, and properly documented for future property transactions.
Complying with Building Regulations and Other Legal Requirements
Building regulations approval is a separate process from prior approval.
These rules cover structural safety, fire safety, drainage, insulation, and ventilation.
You'll need to submit a building regulations application to your local authority or an approved inspector before construction begins.
A building control officer will inspect your work at key stages to make sure everything complies.
Your extension can't cause issues like loss of light to neighbouring properties beyond what was assessed during prior approval.
It's worth checking if your property has any restrictive covenants or other legal requirements that might affect your right to extend.
If your extension is built on or near a boundary with a neighbour, you might need a party wall agreement.
If the Party Wall Act applies, you must notify neighbours in writing at least two months before work starts.
Lawful Development Certificates and Best Practice
A Lawful Development Certificate (LDC) gives formal confirmation that your extension complies with planning rules.
It's not mandatory, but it protects you if questions come up during future property sales or mortgage applications.
You can apply for an LDC before or after construction.
Some homeowners wait until completion to apply for a certificate of lawfulness for an existing development.
This confirms the work was carried out lawfully.
Keep all approval documents, building regulations certificates, and construction records somewhere safe.
They'll prove your extension was built correctly and help you avoid complications when selling.
Frequently Asked Questions
Understanding the rules for larger rear extensions can bring up all sorts of questions about measurements, procedures, and legal requirements.
Let's dig into some common ones.
What are the specific criteria for qualifying a rear extension as a larger rear extension under current regulations?
A larger rear extension qualifies under specific size limits based on your house type.
For detached houses, the extension must project over four metres and up to eight metres beyond the rear wall of the original house.
For all other house types—including semi-detached and terraced properties—the extension must project over three metres and up to six metres.
The extension must be single-storey only.
The maximum height can't go above four metres, and the eaves must stay under three metres.
The extension also can't cover more than half the land around the original house.
Your house can't be a flat, maisonette, or located in a conservation area.
The "original house" means the property as first built, or as it stood on 1 July 1948 if it was built before then.
Can you outline the step-by-step process for obtaining prior approval for a rear extension in a residential property?
Start by completing a prior approval application form for your local planning authority.
This form asks for detailed plans showing the extension's dimensions, height, and materials.
You'll also need site plans that clearly show the extension's position relative to your property boundaries.
Your local authority will consult with your adjoining neighbours about the proposal.
This gives neighbours a chance to review your plans and raise any concerns.
The planning authority then decides whether the extension would have an acceptable impact on neighbouring properties' amenity.
If no objections come up, or if they're not considered significant, your prior approval gets granted.
The whole process usually takes up to 42 days from submission.
In what scenarios is a homeowner exempt from seeking prior approval for constructing a rear extension?
You don't need prior approval if your single-storey rear extension stays within standard permitted development limits.
For detached houses, that's no more than four metres beyond the rear wall.
For other house types, the limit's three metres.
If your extension is within these smaller dimensions, you can go ahead under normal permitted development rights without any application.
You still need to meet all other permitted development criteria, like height restrictions and material requirements.
Permitted development rights don't apply if your property is a listed building, flat, or maisonette.
Properties in conservation areas, Areas of Outstanding Natural Beauty, or National Parks face extra restrictions.
What are the potential consequences of failing to secure prior approval before commencing construction on a large rear extension?
Building without prior approval when it's required breaks planning rules.
Your local planning authority can serve an enforcement notice that forces you to remove the unauthorised extension.
This could mean tearing down the entire structure at your own expense—no one wants that.
You might face prosecution in the magistrates' court for ignoring an enforcement notice.
Fines can be unlimited, depending on how serious the breach is.
Unauthorised work will also cause problems when you try to sell your property.
Solicitors will spot the planning breach during searches, and buyers usually pull out or demand a big price reduction.
You could also struggle to get building insurance for a property with unauthorised development.
How do the requirements for prior approval for rear extensions differ within conservation areas or listed buildings?
You can't use the larger home extension scheme in conservation areas.
That means you can't extend beyond the standard permitted development limits of three or four metres without full planning permission.
Listed buildings require listed building consent for any alterations, no matter the size.
You'll need to submit a full planning application instead of relying on permitted development rights.
The assessment process considers how the work would affect the building's special architectural and historic interest.
If your property is in an Article 4 Direction area, you might face extra restrictions that remove permitted development rights entirely.
Check with your local planning authority to see if your property falls within one of these areas.
PlanSure helps homeowners decide early whether PD or full planning is the safer route.
What is the typical timeframe for a local planning authority to decide on a prior approval application for a rear extension?
The local planning authority gets 42 days from the day they receive your application to make a decision. This window covers the neighbour consultation and their review of any objections.
If they don't respond within those 42 days, you can go ahead with your extension as though you have prior approval. That said, you still need to meet every other requirement in the larger home extension scheme.
They might ask you for more information while they're assessing your application. If you don't get back to them quickly, it could slow things down or even lead to a refusal.
PlanSure helps homeowners decide early whether PD or full planning is the safer route.