Jan 17, 2026
Planning an extension for your home can feel overwhelming. You might worry about permission requirements and navigating those confusing rules.
Honestly, figuring out what you need doesn't have to be a nightmare. It just takes a bit of upfront knowledge.
In many cases, you can build a house extension without applying for planning permission if it falls under permitted development rights, though specific limits and conditions must be met. These rules depend on the size and location of your extension, plus whether your home sits in a protected area.
If your plans go beyond permitted development limits, you'll need to submit a formal planning application to your local council.
This guide covers the most common questions about planning permission for extensions in 2026. You'll find out when you need permission, what the rules are for different types of extensions, and how to avoid expensive mistakes.
Key Takeaways
Many house extensions qualify as permitted development and don't require planning permission if they meet specific size and location rules.
Extensions in conservation areas, listed buildings, or properties with Article 4 directions usually need full planning permission.
Building regulations approval is separate from planning permission and is required for most extension projects regardless of permitted development status.
Do You Need Planning Permission for Extensions?
You can often extend under permitted development rights, but there are limits on size and location. Planning permission kicks in when your project exceeds these limits or your property sits in a restricted area.
Permitted Development Rights Explained
Permitted development rights let you extend your home without applying for planning permission, as long as you stay within certain boundaries. Your extension can only cover up to half the land around your original house.
The materials on the outside should match your current house. Single-storey rear extensions can't go more than four metres back for detached houses or three metres for others. The height can't exceed four metres.
You can't build extensions forward of your main front wall or side wall if it faces a road.
Side extensions must be single storey, can’t go higher than four metres, and can only be up to half the width of your original house. Multi-storey extensions have stricter rules—they can't extend beyond your rear wall by more than three metres and must stay at least seven metres from any opposite boundary.
You can't build higher than your existing roof or add things like balconies or raised platforms.
When Planning Permission Is Mandatory
You'll need planning permission if your extension goes beyond permitted development limits or your property has restrictions. Flats and maisonettes don't get permitted development rights for extensions—so you always have to apply.
Properties in conservation areas, National Parks, Areas of Outstanding Natural Beauty, or World Heritage Sites face tighter restrictions. All side extensions and multi-storey rear extensions in these designated areas require planning permission.
Some properties have Article 4 directions that remove permitted development rights entirely. Always check with your local planning authority.
Listed buildings always need planning permission for extensions, no matter the size. Houses created through changes of use can't use permitted development rights either.
Previous extensions count towards your limits. If earlier owners built extensions, that reduces what you can add now.
How Prior Approval Applies to Extensions
Prior approval is a simpler process for larger single-storey rear extensions. You can extend up to eight metres for detached houses or six metres for others, beyond the standard three or four-metre limits.
This only works for properties not on designated land. You must submit a prior approval application before starting work.
Neighbours get notified and have 21 days to comment. The council has 42 days to decide if the extension's impact is acceptable.
Prior approval focuses on specific issues: the extension's design, its appearance, and how it affects neighbours. The process is usually faster and less expensive than full planning permission.
Types of House Extensions and Relevant Rules
Different extension types come with different size limits and rules. Single-storey rear extensions usually get the most generous allowances, while two-storey extensions face stricter height and depth restrictions.
Single-Storey Rear Extensions
Single-storey rear extensions benefit from the most flexible permitted development rules. Detached houses can extend up to 8 metres from the rear wall of your original home.
For semi-detached and terraced houses, the limit is 6 metres. The extension can't be taller than 4 metres.
If it's within 2 metres of your boundary, the height must not exceed 3 metres. The eaves height can't be higher than the existing eaves.
Your extension can't cover more than 50% of the total curtilage (excluding the area of your original house). This 50% includes all extensions and outbuildings.
If you want to go beyond the standard limits, you might qualify for the larger home extension scheme. That allows up to 8 metres for terraced and semi-detached homes, but you'll need to consult your neighbours first.
Side Extensions and Side Returns
Side extensions have tighter restrictions. Your side extension can't be taller than 4 metres, or cover more than 50% of the total curtilage when combined with other buildings.
The extension must be single-storey if it's within 7 metres of the boundary facing the highway. For properties on designated Article 2(3) land, including conservation areas, side extensions require planning permission.
Side return extensions (filling the gap between your house and boundary) count as side extensions under permitted development rules. They're popular in terraced houses but must meet single-storey height limits.
Your side extension can't extend beyond the front wall of your original home. The width is restricted to keep the extension looking smaller than the main house.
Two-Storey Extensions and Loft Conversions
Two-storey extensions have much stricter limits. They can't extend more than 3 metres beyond the rear wall of your original house.
The extension can't be higher than the highest part of your existing roof. Two-storey side extensions usually need planning permission, especially if they'd change your home's appearance a lot.
The 50% curtilage rule still applies. Loft conversions have their own permitted development rules under Class B.
The extra roof space can't go over 50 cubic metres for terraced houses or 40 cubic metres for detached and semi-detached houses. Dormer windows can't be on the principal elevation or extend higher than the existing roof ridge.
Materials should match your existing house as closely as possible.
Special Considerations: Conservation Areas, Listed Buildings, and Restrictions
Properties in protected areas face stricter planning controls than standard homes. Conservation areas and listed buildings require extra consent for extensions, and Article 4 directions can remove normally permitted development rights.
Extensions in Conservation Areas
Conservation areas are zones your local planning authority designates for their special architectural or historical interest. They want to preserve or improve the character and appearance of these areas.
Many permitted development rights don't apply in conservation areas. You'll need planning permission for rear extensions over certain size limits.
Single-storey rear extensions over 3 metres (terraced houses) or 4 metres (detached and semi-detached houses) need approval. External alterations visible from public areas get extra scrutiny.
Your local authority will assess how your extension affects the area's character. Features like rooflines, materials, windows, and boundary treatments usually need to match existing styles.
Check your council's Conservation Area Appraisal, which details the features that define your area's significance. Side extensions and roof extensions often require planning permission in conservation areas, even if they'd be permitted development elsewhere.
Your proposal needs to show that it preserves or enhances the local character.
Extensions to Listed Buildings
Listed buildings appear on the National Heritage List for England and have legal protection. You need both planning permission and Listed Building Consent for extensions that affect the building's character.
Listed Building Consent covers all works affecting the building's historic character, including internal changes. The application process looks at how your extension impacts the building's significance.
You'll likely need to submit a heritage statement explaining the building's importance and how your design minimises harm. Decision-makers must give "special regard" to preserving the building and its features.
Traditional materials and sympathetic designs are essential. Repair and retention of original features is always preferred over replacement.
Historic England has guidance on maintaining listed buildings, and hiring a conservation architect is often worth it for complex projects. Even small extensions get careful assessment.
The council expects you to justify any harm to heritage significance, so approval is tough unless your proposal shows exceptional merit.
Article 4 Directions and Other Local Restrictions
Your local planning authority can remove permitted development rights using an Article 4 direction. These directions protect areas where normal permitted development would harm local character or heritage.
Article 4 directions are common in conservation areas but also show up elsewhere, like Areas of Outstanding Natural Beauty and around Sites of Special Scientific Interest. Always check with your council before assuming you have permitted development rights.
Many councils publish Article 4 direction maps online. When an Article 4 direction applies, you must submit a planning application for work that would normally be permitted development.
This doesn't mean permission will be refused—it just requires formal assessment. Your local authority will look at whether the proposal fits in with the protected area's character.
Different Article 4 directions cover different types of work. Some restrict only certain changes like roof extensions or cladding, while others remove broader permitted development rights.
The Planning Application Process
When permitted development rights don't cover your extension, you have to submit a formal planning application to your local council. The process involves preparing detailed plans, consulting neighbours, and waiting for a decision—usually around eight weeks for householder applications.
Pre-Application Advice and Planning Consultants
Most local councils offer pre-application advice before you submit anything official. This service lets you chat with a planning officer about your plans and spot any issues early.
Pre-application advice costs differ by council, usually between £50 and £300, depending on your project's complexity. You'll get written feedback on whether your proposal is likely to get approved.
Planning consultants can run the whole planning application process for you. They charge between £500 and £2,000 but know local policies and can strengthen your application.
Many homeowners hire consultants after objections or for conservation area projects. You don't legally need a consultant for a householder application, but their expertise can save time and boost your chances—especially for tricky extensions.
Required Plans and Documentation
Your planning application needs specific drawings and documents. The Planning Portal asks for a location plan at 1:1250 scale showing where your property sits relative to nearby streets and buildings.
You'll also need a block plan at 1:500 or 1:200 scale. This shows your property boundaries, the proposed extension, and measurements from boundaries.
Include existing and proposed elevations showing all four sides of your house before and after the extension.
Most applications need:
Existing and proposed floor plans at 1:50 or 1:100 scale
Site plan showing parking and access
Design and Access Statement (sometimes)
Application form and fee (£206 for householder planning permission in 2026)
Your architect or designer usually prepares these drawings. They must be accurate and clearly labelled with measurements, materials, and colours.
Neighbour Consultation and Objections
After receiving your application, your local council runs a neighbour consultation scheme. They send letters to properties next to yours and put up a notice near your home.
Neighbours get 21 days to comment or object. Common neighbour objections include worries about:
Loss of privacy or overlooking
Overshadowing or loss of light
More noise or disturbance
Impact on property values isn't a planning reason, but people bring it up anyway. You can't stop neighbours from objecting, but thoughtful designs that respect privacy and light reduce complaints.
The planning officer weighs objections against planning policy when making a decision. Only valid planning issues count.
Decision Timelines and Outcomes
The council has eight weeks from validation to decide on householder applications. You'll get one of three outcomes:
Approved – You can start building once you receive your planning approval notice. Approval usually includes conditions, like matching materials or limits on working hours.
Refused – The notice explains why your application failed. You can appeal within six months or submit a revised application.
Withdrawn – You can withdraw your application before a decision if big issues come up. You won't get your fee back, but you can submit a new application.
Check your planning approval conditions carefully before starting work. Breaking conditions can trigger enforcement action and force you into a retrospective application.
PlanSure helps homeowners decide early whether PD or full planning is the safer route.
Building Regulations and Other Legal Requirements
Planning permission and building regulations aren't the same thing. Building regulations keep your extension safe and energy efficient.
The Party Wall Act steps in to protect your neighbours when you're building near shared boundaries.
Building Regulations Approval
You'll need building regulations approval for any extension, even if planning permission isn't required. This covers things like structural safety, fire protection, insulation, ventilation, drainage, and electrics.
There are two ways to apply. A Building Notice lets you start work fast—just 48 hours—but it's less certain.
A Full Plans Application takes 5-8 weeks, but you get formal approval before you build. Lenders and solicitors usually prefer this route.
Inspectors check your work at key stages: foundations, damp proofing, drainage, before plasterboard, and at completion. Let building control know 48 hours before each visit.
Don't cover up work before it's checked. If you do, you might have to rip things open later, which gets expensive.
Expect to pay £800-1,500 for local authority fees, plus another £500-1,200 for a structural engineer. When you're done, you'll get a completion certificate—hang onto it, as you'll need it if you ever sell.
Building Regulation and Architectural Drawings
Building regulation drawings are technical—they show exactly how your extension will meet safety and performance rules. They're not the same as architectural drawings, which focus more on how things look.
Your building regulation drawings need to show floor plans, elevations, foundation details, structural calculations, and specs for insulation, ventilation, and drainage. Architectural drawings just show the design, not the technical stuff building control wants.
Most architects and designers handle both sets of drawings for you. Building regulation drawings usually cost £400-800 as part of a full design package for a typical extension.
The Party Wall Act and Boundary Issues
The Party Wall Act 1996 kicks in when you build on or close to a boundary you share with your neighbours. You'll need to serve a party wall notice if you're building on the line, digging within 3 metres of someone else's building, or working on a shared wall.
Serve your notice at least two months before work for new structures, or a month for other jobs. Your neighbour can agree or disagree.
If they disagree, you'll both need party wall surveyors to draw up an award document. That usually costs £700-1,500 per neighbour.
Check your title deeds to confirm your property boundaries before you design anything. The boundary of the curtilage defines what you actually own.
Right to light is a different legal issue. Neighbours can object if your extension blocks natural light to their windows, especially if they've had that light for over 20 years.
Common Challenges and Extension Costs
Getting planning permission for an extension isn't always straightforward. There are plenty of pitfalls that can slow you down or push up your costs.
Overdevelopment rules, higher application fees, and the risks of building without permission all play a part.
Overdevelopment and Design Limitations
Your local council will decide if your extension counts as overdevelopment. Basically, if it's too big for your plot or looks out of place, you're in trouble.
They'll check how much garden you have left and whether the design fits in with the neighbours. If your extension swallows up too much land or dominates the street, expect a refusal.
Flats and maisonettes get more scrutiny. They often have less outdoor space and more shared boundaries, so the rules are stricter.
If you do get approval, there might be strings attached. Councils can restrict materials, window positions, or building height to protect privacy and keep the street looking good.
Corner plots and conservation areas face even tighter controls. It's smart to work with an architect from the start—they'll help you design something that stands a better chance of getting through.
Final Costs and Application Fees
Extension costs depend on size, materials, and where you live. It's not just the build—you've got to budget for professionals and paperwork too.
From April 2025, planning permission for an extension in England costs £528 for householder applications. That's more than double the old fee.
You'll need architectural drawings, structural calculations, and maybe specialist reports. These extras can add £1,000 to £3,000, depending on how tricky things get.
Building regulations approval is separate and usually costs £500 to £1,200. If you need prior approval or a party wall agreement, expect more surveyor and legal fees.
Always keep a contingency fund—aim for 10-15% of your total budget. Surprises and changes happen.
What Happens If You Build Without Permission?
If you build an extension without the right planning permission, your council can step in. They might make you apply after the fact, change the structure, or even tear it down.
Retrospective applications aren't a sure thing. If you're refused, demolition and putting things back can get expensive fast.
Enforcement action can happen within four years for most breaches—or ten if you tried to hide the work. Selling gets complicated too. Buyers and solicitors will want proof of planning consent.
If you can't provide it, buyers might walk away. Indemnity insurance is an option, but it doesn't stop council enforcement. It's just not worth the risk—always check before you start.
Frequently Asked Questions
Extension projects bring up all sorts of questions. There are size limits, special rules for protected areas, and timelines that seem to stretch forever.
Listed buildings and conservation areas? They're a different beast. Neighbours have their own rights too.
What are the size limits for a single-storey extension without requiring planning permission?
For single-storey rear extensions, you can go up to four metres beyond the rear wall if you have a detached house. For others, it's three metres.
Under the larger home extension scheme, these limits jump to eight metres for detached homes and six metres for others, but you'll need prior approval.
The extension can't be taller than four metres. Side extensions must stay under four metres in height and can't be wider than half the width of your original house.
Extensions and other buildings can't cover more than half your garden. Materials need to match your home's exterior.
How do the regulations for extensions differ in conservation areas?
Conservation areas are under Article 2(3) land, so permitted development rights are limited. All side extensions in these areas need full planning permission, no matter the size.
Rear extensions with more than one storey also need planning permission. For single-storey rear extensions, the standard limits apply, but you can't use the larger home extension scheme.
Cladding isn't allowed under permitted development in conservation areas. Sometimes, your local authority puts an Article 4 direction in place, removing even more rights.
Can neighbours object to a permitted development extension?
Neighbours can object if your extension needs prior approval—like those bigger single-storey rear extensions. The council will notify them and consider what they say.
For standard permitted development that skips prior approval, neighbours can't formally object through planning. But they can report you if they think you've broken the rules.
If your extension doesn't meet the permitted development limits, you'll need a full planning application. At that point, neighbours can comment during the consultation.
What constitutes a material change of use when extending a residential property?
A material change of use means you're using your property in a new way that needs planning permission. Extensions themselves usually don't trigger this, but how you use the new space might.
If you turn part of your home into a separate dwelling, that's a material change of use. Running a business that brings in lots of traffic or noise might also need permission.
If you're building an annexe for family, that's still residential use. But if it's a fully separate unit with its own facilities, you'll likely need permission as a new dwelling.
How long does one typically have to wait for planning permission approval for an extension?
Councils aim to decide on householder planning applications within eight weeks. If your case is complex, they might ask for more time.
Prior approval applications for bigger single-storey extensions usually take 42 days. Sometimes, the council stretches this to 49 days to consult neighbours.
You'll get a notice with the decision—approval, refusal, or conditions. If you don't hear back in time, you can appeal to the Planning Inspectorate.
PlanSure helps homeowners decide early whether PD or full planning is the safer route.
What are the implications of extending a listed building?
Listed buildings need listed building consent for any work that could affect their special architectural or historic value. This covers both external and internal changes, no matter how big or small—even extensions.
You can't use permitted development rights for listed buildings. Even something as small as swapping out windows or adding a roof light needs listed building consent.
The approval process usually drags on and asks for detailed info about your building's history and significance. A conservation officer from your local planning authority will look closely at how your extension might change the building's character or setting.
If you go ahead without consent, you could face criminal prosecution. They might even force you to undo any unauthorised changes.