Dec 28, 2025
Planning a home extension can feel overwhelming, especially if you’re not sure about needing formal approval from your local council.
Many home extensions in the UK fall under permitted development rights, which allow you to build without applying for planning permission, provided you meet specific size limits and conditions. Knowing these rules before you start work can save you money, time, and maybe a few headaches.
Permitted development rules vary from one location to another. They depend on your property type, your location, and how big you want your extension to be.
What works for a detached house differs from what works for a semi-detached or terraced property. If you live in a conservation area or your property has restrictions, you might need planning permission even for small changes.
This guide covers planning permission for extensions—from the basics to the application process.
You'll see when you can use permitted development, when you need formal approval, and how to dodge mistakes that could slow down your project or get you in trouble with the council.
Key Takeaways
Most single-storey rear extensions fall under permitted development if they meet size limits of 4 metres for detached houses or 3 metres for other properties.
Properties in conservation areas, listed buildings, or with Article 4 directions need planning permission even for small extensions.
Building Regulations approval is separate from planning permission and is required for nearly all extension work, regardless of permitted development status.
Understanding Planning Permission and Permitted Development
Planning permission is formal approval from your local planning authority for building work. Permitted development rights let you make some home improvements without that approval.
The difference between these two determines if you need to fill out an application or can just get started.
What Is Planning Permission?
Planning permission is official authorisation from your local planning authority before you carry out certain types of work on your property.
Your local council checks to see if your extension fits national planning rules and the character of your area.
You’ll need to submit plans and drawings showing your extension’s design, size, and location. The council looks at whether your plans follow local development policies and considers how your project might affect neighbours, traffic, or the local environment.
The application process usually takes about eight weeks for standard cases. Neighbours might get consulted, and planning officers will weigh your proposal against set criteria before making a decision.
What Are Permitted Development Rights?
Permitted development rights let you extend or improve your home without applying for planning permission, as long as your work won’t have a big impact.
These rights are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015.
There are strict size limits and conditions. For example, single-storey rear extensions can usually go up to 4 metres for detached houses.
Permitted development rights don’t apply to flats, homes created through change of use, or properties in conservation areas. Your council might have removed these rights with an Article 4 Direction too.
Key Differences Between Planning Permission and Permitted Development
The main difference is the approval process and how much flexibility you get.
Planning permission means you submit a formal application with detailed plans. Permitted development follows pre-approved national guidelines.
Planning permission lets you propose bigger or taller extensions, but your council has to sign off on the design and impact.
Permitted development is faster—no application fees, no long waits. But you have to stick to fixed size limits and conditions.
Your choice depends on your extension’s size and design. Smaller, standard extensions often fit under permitted development, but bigger or more unusual projects will need planning permission.
Do I Need Planning Permission for My Extension?
Most home extensions in the UK can go ahead under permitted development rights, but it depends on your property, the size of your extension, and where you live.
You’ll need planning permission if your project goes over size limits, affects a listed building, or is in a conservation area.
Common Projects Requiring Permission
You need to apply if your extension is too big or tall. Two-storey extensions that go more than 3 metres past the rear wall of a detached house need approval.
Side extensions wider than half your property’s original width also need permission.
Conservation areas have stricter rules. Any side or rear extension needs planning permission there, no matter the size.
Listed buildings always require approval for any changes. Permitted development rights don’t apply.
If your project creates a separate dwelling or changes your property’s use, you definitely need permission. Extensions that affect your neighbours’ light or privacy might also need approval from your local planning authority.
Extensions Allowed Without Permission
If you own a detached house, you can build a single-storey rear extension up to 6 metres from the back of your home.
Semi-detached and terraced houses can go up to 3 metres without permission under permitted development rights.
Kitchen extensions usually fit these rules if they stay within the size limits. The extension can’t go over 4 metres high or past the original roofline.
Side extensions are fine if they’re single-storey and no taller than 4 metres. They can’t take up more than half the width of your original house.
You can extend your home without planning permission if you use materials that match your existing property. The work must stay within your property boundaries and not face a main road.
How to Check If You Need Approval
Contact your local planning authority to see if your project qualifies as permitted development. They keep records of any restrictions.
Check if previous owners have already used up your permitted development rights. Extensions built after 1948 might have used these allowances.
Look at your property deeds for any restrictive covenants that could block building work, even if planning rules allow it.
Try the Planning Portal’s interactive house tool to measure your extension against the limits for your property type. Always double-check before you start.
If you’re not sure, talk to planning permission professionals. They can look at your plans and give you advice.
Permitted Development Limits and Exceptions
Permitted development rights have clear size limits, material rules, and situations where they don’t apply. Knowing these details helps you figure out if you need full planning permission.
Size and Height Restrictions
Single-storey rear extensions have different limits based on house type.
Detached houses can go up to four metres from the original rear wall. Semi-detached and terraced houses are limited to three metres.
There’s a special scheme with prior approval where these limits can increase. Detached houses can build up to eight metres deep, and others up to six metres.
Multi-storey extensions have stricter rules. They can’t extend more than three metres beyond the original rear wall and must stay at least seven metres from any boundary opposite the rear wall.
Side extensions must be single storey and under four metres in height. They’re limited to half the width of your original house.
Extensions can’t be higher than your existing roof or higher at the eaves than your current eaves.
If your extension comes within two metres of a boundary, the eaves can’t go over three metres high.
Material and Design Rules
Any exterior work must use materials that look similar to your existing house. This helps extensions blend in and not stick out.
Permitted development rights ban certain features. You can’t add verandas, balconies, or raised platforms.
You can’t alter your existing roof as part of the extension.
For multi-storey extensions, the roof pitch should match your house if possible. Upper-floor windows on the side must use obscure glass and stay non-opening unless the opening part sits more than 1.7 metres above the floor.
Only half the land around your original house can be covered by extensions or outbuildings. This includes any previous extensions.
When Permitted Development Rights Do Not Apply
Permitted development rights don’t exist for flats or maisonettes. These always need planning permission for extensions.
Houses created through changes of use or conversions lose these rights too. If your home was once a shop or barn, you’ll need full planning permission.
Article 2(3) designated land covers conservation areas, National Parks, Areas of Outstanding Natural Beauty, and World Heritage Sites. In these places, all side extensions need planning permission, and rear extensions over one storey need approval.
Article 4 directions can remove permitted development rights in certain areas. Councils issue these, often in conservation areas or near listed buildings. Check with your council to see if any restrictions apply.
Listed buildings never have permitted development rights for extensions. You’ll need listed building consent and planning permission for any changes.
Special Designations and Restrictions
Some properties face stricter rules that limit or remove permitted development rights. Conservation areas, listed buildings, and protected landscapes need extra permissions—even for small changes.
Conservation Areas and Article 4 Directions
Conservation areas restrict what you can build without approval.
Your council can remove permitted development rights through an Article 4 Direction. That means you’ll need full planning permission for extensions that would normally be allowed.
These directions are common in historic town centres or areas with special character. Even a small extension within standard size limits needs an application if your property has this restriction.
Check your council’s planning website or contact them to see if an Article 4 Direction affects your home. This should show up in local searches when you bought the property, but it’s worth double-checking.
Listed Buildings and Protected Land
Listed building consent is needed for any work that affects the character of a protected structure, no matter the size.
This applies separately from planning permission and covers both internal changes and extensions.
Grade I, Grade II*, and Grade II listings all require you to show your proposal preserves or enhances what’s special about the building. The process takes longer and often needs heritage statements and detailed drawings.
Listed buildings have no permitted development rights for extensions. You’ll always need both listed building consent and planning permission.
Areas of Outstanding Natural Beauty and National Parks
If your property’s in an Area of Outstanding Natural Beauty, National Park, the Broads, or a World Heritage Site, the permitted development limits are tighter.
Single-storey rear extensions are capped at 3 metres for terraced and semi-detached houses, and 4 metres for detached homes—less than usual.
Side extensions and roof changes need planning permission in these protected places. The rules aim to keep these areas looking the way they should.
Expect your council to look closely at your design, materials, and the impact on the landscape.
Navigating the Planning Application Process
If you find out your extension needs planning permission, you’ll have to put together a formal planning application for your local council.
You’ll need detailed documents and drawings, and then you’ll wait for the council to review everything. Neighbours or planning officers might raise concerns, which you’ll have to address along the way.
How to Apply for Planning Permission
You can submit your householder planning permission application through the Planning Portal. This is the government’s main online gateway for planning applications.
Most councils now want you to apply electronically through this system.
Before applying, think about getting pre-application advice from your local planning authority. There’s a fee, but you’ll get to discuss your plans with a planning officer before you submit anything official.
They might spot issues early and suggest changes that could boost your chances.
The application form asks for details about your property, the extension, and supporting documents. You’ll need to pay an application fee, which usually falls between £206 and £462 for most home extensions.
Double-check all your info—mistakes can slow everything down.
Key Application Documents and Plans
Your planning application needs several technical documents. Scaled drawings are a must.
You’ll have to include a site location plan, a block plan to show the extension’s footprint, and elevation drawings from all sides.
A design statement explains why you want the extension, what materials you’ll use, and how it fits in with the area. This helps the planning officer see your reasoning and shows you’ve thought about the surroundings.
Depending on where you live, you might need specialist reports. Flood risk assessments, ecology surveys, or heritage statements could be necessary.
Your architect or planning consultant should know what’s required for your situation.
All plans need to be drawn to scale and clearly labelled. Poor or incomplete drawings often get applications rejected.
Understanding the Planning Permission Timeline
The standard timeline for planning permission is 8 weeks from when your council gets a valid application. For more complicated projects or if you agree to an extension of time, it can stretch to 13 weeks.
Your application goes through a few stages. First, the planning officer checks if you’ve included all the documents.
If something’s missing, they’ll ask for it and the clock pauses.
Then the council puts your application out for public comment, usually for 21 days. Neighbours get letters, and anyone can look at your plans online.
The planning officer reviews your application against local policies and any objections. After that, they make a recommendation.
You’ll get a decision notice by post. It’ll say if permission is granted, refused, or approved with conditions.
If you get approval, you usually have three years to start work.
Neighbour Consultation and Objections
Neighbour consultation is a key part of the planning process. Your council will let nearby properties know about your extension so they can look at the plans and comment.
Neighbours often worry about losing light, privacy from new windows, construction noise, or how the extension will look. Extensions shouldn’t block light or invade privacy, so sometimes you’ll need frosted glass for side windows.
If neighbours object, the planning officer weighs their concerns against planning policy. Only objections about things like overshadowing, overbearing impact, or loss of privacy count.
You can respond to objections by sending in more info or tweaking your plans. Chatting to neighbours before you apply often heads off formal complaints.
Show them your plans, be open about your intentions, and try to address any worries.
Building Regulations and Further Legal Considerations
Building regulations approval is required for almost all extensions, no matter the size. These rules cover structural safety, fire protection, insulation, and drainage.
If you’re working near boundaries, you’ll also need to think about party wall requirements and make sure you follow modern fire safety standards.
Building Regulations Approval vs Planning Permission
Building regulations and planning permission aren’t the same thing. Planning permission is about how your extension looks and affects the area.
Building regulations approval checks that your extension is safe and energy-efficient.
You might be able to extend under permitted development without planning permission, but building regulations approval is still mandatory. A lot of homeowners miss this.
For approval, you’ll need detailed drawings showing foundations, walls, insulation, and drainage. You can apply with a Full Plans application (for advance approval) or a Building Notice (quicker, but riskier if issues crop up during the build).
Role of Building Control and Compliance
Building control officers check your extension at key stages to make sure you’re following the rules. You must let them know before you start work and at points like foundation digging, installing the damp-proof course, drainage connections, and when you finish.
Most authorities want 24 to 48 hours’ notice before inspections. If you miss inspections, you could face enforcement action or trouble selling your home.
Building control looks at:
Structural integrity – foundations, walls, roof
Energy efficiency – insulation, heating controls
Ventilation – air flow, moisture control
Drainage – connection to existing systems
Once you pass all checks, you’ll get a completion certificate. Keep this safe—buyers will want to see it someday.
Party Wall and Boundary Issues
The Party Wall Act 1996 kicks in if you build on or near a shared boundary. You need to serve notice to neighbours at least two months before work starts for most party wall matters.
A party wall agreement protects you and your neighbours if there’s any damage or structural issues. If your neighbour doesn’t agree, both sides appoint surveyors to hammer out a formal agreement.
Costs usually range from £700 to £1,000 for simple cases. Skipping a party wall agreement can lead to legal headaches, building delays, and bad blood with neighbours.
The Act covers building on boundary lines, digging near neighbouring foundations (within three to six metres, depending on depth), and work to shared walls.
Fire Safety and Structural Standards
Fire safety standards have tightened up in recent years. Extensions need fire-resistant materials in walls, floors, and ceilings—especially when close to boundaries.
The exact fire resistance rating depends on the type of extension and how close it is to other properties.
Loft conversions must have proper escape routes, either through protected stairways or compliant escape windows. Ground and first-floor extensions usually have less strict requirements, but you still need to think about preventing fire spread.
You have to install mains-powered smoke alarms with battery backup in hallways and landings on every floor. These alarms should be linked so if one goes off, they all do.
Structural rules make sure your extension won’t collapse or damage the existing building. Building control checks foundation depth, wall thickness, beam sizes, and roof construction for your design and ground conditions.
Costs, Consultants, and Common Mistakes
Planning applications come with fees and sometimes professional costs, which vary across the UK. Knowing what to expect helps you budget and avoid problems.
Typical Planning Permission Costs
Planning permission costs went up in April 2025. Householder application fees are now £528 in England, £230 in Wales, £346 in Scotland, and £347 in Northern Ireland.
If you’re building something separate from your house, like a garden office, the fee drops to £262 in England. The Planning Portal also charges an £85 admin fee on top.
You’ll probably need architectural drawings and maybe surveys. Extra drawings or changes can bump up your costs.
If your application gets rejected, you’ll pay the full fee again to resubmit. Fees go up each year with inflation.
Working with Planning Consultants
A planning consultant manages your application, deals with case officers, and handles surprises. Consultants who’ve worked both for councils and as applicants know the system inside out.
They help you spot risks and make smart decisions about your design. Sometimes you’ll need to compromise on roof pitch, materials, or the size of the extension.
It’s an extra cost, but it can save you from refusals and expensive re-applications.
Planning advice is especially helpful when permitted development rights get tricky, like with listed buildings or conservation areas.
Common Reasons for Refusal and How to Avoid Them
Design issues are a top reason for rejection. Extensions that don’t fit the house or area, are too big, or harm the street scene often get turned down.
Neighbour impacts also cause refusals—think overlooking windows, overshadowing gardens, or an overbearing feel. Talking to neighbours early can prevent objections.
Technical problems can trip you up too:
Flood risk
Impact on protected trees
Wildlife habitat disruption
Not enough parking
Green belt restrictions
Set your priorities before applying. If you care most about speed and budget, stick to permitted development rights.
If you want to maximise space, get ready for a longer, more ambitious process.
Keeping Records and Ongoing Obligations
After you get approval for your extension, you’ll need to keep good records and know the deadlines and conditions attached. These documents protect your investment and prove you followed the rules if you ever sell or face questions about the work.
Lawful Development Certificates and Approvals
A lawful development certificate is official proof that your extension meets planning permission for extensions or permitted development rules. Keep all approval documents safe—this means the decision notice, approved drawings, and any condition discharge approvals.
If you built under permitted development and didn’t get planning permission, you can apply for a lawful development certificate to prove the work was legal. This is especially important when selling, since buyers and solicitors will want proof that everything’s above board.
Hang on to building regulations completion certificates too. These are separate from planning permission but just as important.
Store copies of all correspondence with your planning authority, including emails and letters about conditions or changes.
Planning Permission Validity Period and Conditions
Planning permission for extension usually lasts three years from approval. You need to start building within this period, or you’ll have to reapply.
Most approvals come with conditions you have to meet before or during construction. Common ones are submitting material samples, providing drainage details, or limiting working hours.
You must discharge these conditions by sending the right info to your council before carrying on with that part of the build.
Track all your condition discharge submissions and approvals. If you build without meeting mandatory conditions, the council can take enforcement action even if you have planning permission.
Some conditions apply throughout the build, others just before certain stages.
Frequently Asked Questions
UK home extension rules have specific size limits, consultation steps, and property differences that affect whether you need planning permission. Extensions over 100 square metres might mean extra charges, and building without approval can mean you’ll have to alter or tear down the work.
What are the size limits for a single-storey extension without requiring planning permission?
Single-storey rear extensions have set size limits depending on your property type. If you own a detached house, you can extend up to four metres from the back wall of the original house.
For semi-detached and terraced houses, the limit is three metres.
These limits are for standard permitted development rules. You might be able to go further under the larger householder extension scheme.
With this scheme, detached houses can extend up to eight metres, and other houses up to six metres. But you’ll need prior approval from your local planning authority, and it only applies if your property isn’t in a protected area.
The height of a single-storey extension can’t go over four metres. You also can’t cover more than half the land around the original house with extensions and outbuildings combined.
How does the 'Neighbour Consultation Scheme' affect my home extension plans?
The Neighbour Consultation Scheme kicks in when you want to build a larger single-storey rear extension that goes beyond the usual permitted development limits. Your local planning authority has to notify your neighbours about your plans and give them 21 days to share any comments.
If your neighbours have concerns, the council decides if prior approval is needed. They look at things like loss of light, privacy, and how your extension might affect the people next door.
You'll need to submit a prior approval application, including drawings and a location plan. The council gets 42 days to make a decision after they receive your complete application.
This scheme doesn't apply if your home sits in a conservation area, National Park, or other special land. In those places, you must apply for full planning permission for any rear extension over one storey.
Are there different regulations for terraced and semi-detached houses compared to detached homes?
Yep, the rules change depending on your house type. Detached homes can have single-storey rear extensions up to four metres under standard permitted development, while terraced and semi-detached homes are capped at three metres.
With the larger extension scheme, detached houses can go up to eight metres. Terraced and semi-detached homes can only reach six metres, and you'll need prior approval for that.
Side extensions follow the same rules no matter what kind of property you have. They can't be taller than four metres, must be single-storey, and can't be wider than half the width of the original house.
Extensions, no matter the property type, can't cover more than half the land around the original house. The materials you use should match your existing house as closely as possible, though honestly, getting an exact match isn't always simple.
What criteria must be met for an extension project to be considered a 'Permitted Development'?
Your extension has to stay within strict size limits and can't be higher than the existing roof or go above the eaves. Permitted development rights let you make certain changes without full planning permission if you tick all the right boxes.
You can't build the extension in front of the main part of your house that faces the road. If the side of your house faces a highway, you can't build in front of that either.
No verandas, balconies, or raised platforms are allowed. You also can't add a microwave antenna, chimney, flue, or make changes to the roof as part of the extension.
For multi-storey extensions, any windows on the upper floor that face the side must have obscure glazing. These windows should be non-opening unless the part that opens sits more than 1.7 metres above the floor.
If your extension is within two metres of a boundary, the eaves can't be higher than three metres. The materials for the outside should look similar to what's already on your house.
How long does it typically take to obtain planning permission for home extensions?
Usually, a householder planning application takes about eight weeks from validation. The local planning authority aims to decide within that time, though some tricky cases might drag on.
For larger single-storey extensions, prior approval applications get a decision within 42 days. The council will notify your neighbours and give them 21 days to speak up before deciding.
You can track your application's progress on your local planning authority's online portal. Some councils even send updates by email or text, which is actually pretty handy.
If the council doesn't decide within the set time, you can appeal. Most authorities do their best to keep householder applications moving, so you aren't left waiting forever.
What are the potential consequences of building an extension without the necessary planning permission?
Building an extension without the right planning permission is a breach of planning control. Your local planning authority might send you an enforcement notice, telling you to change or even remove the extension.
The council gets up to four years from the time you finish the build to take enforcement action. After those four years, the breach becomes immune from enforcement—though, weirdly, that doesn’t actually make it lawful.
If you ignore an enforcement notice, you could face prosecution or fines. Getting this wrong can lead to costly mistakes, like having to undo the work and start the whole process over.
An unauthorised extension could mess up your plans to sell the property. Solicitors will spot planning breaches during searches, and buyers might back out or push you for a lower price.
If you’ve already built without approval, you can try applying for retrospective planning permission. Still, there’s no guarantee the council will say yes, and you might face enforcement action while they decide.