Dec 29, 2025
You might think planning permission is just about following a checklist of rules. But councils look at much more than measurements and height limits when they review your extension application. Every application is assessed individually based on factors like your street's character, current planning policies, site restrictions, and how your extension fits into the surrounding area.
Understanding what councils actually consider can save you time, money, and disappointment. Two identical extensions on the same street might get different decisions because the specific circumstances of each property matter. Your neighbour's approval doesn't guarantee yours will be approved too.
This guide explains what planning officers really look for when they assess your extension plans. You'll learn how to give your project the best chance of approval by understanding the full picture beyond basic rules.
Key Takeaways
Councils assess each extension application individually based on local character, current policies, and site-specific factors rather than just applying standard rules
Permitted development rights don't apply to all properties and can be restricted by conservation areas, listed building status, or Article 4 directions
Building regulations requirements apply separately from planning permission and cover structural safety, energy efficiency, and construction standards
What Councils Consider When Assessing Extension Applications
Planning officers look beyond basic measurements and permitted development rules when they assess your application. They evaluate how your extension affects the surrounding area, your neighbours, and whether similar projects have been approved nearby.
Local Character and Design Fit
Planning officers assess whether your extension suits the character of your street and neighbourhood. They look at building materials, roof styles, window designs, and the overall appearance of nearby properties. Your extension doesn't need to copy your existing house exactly, but it should look intentional rather than awkward.
In Conservation Areas or near listed buildings, the local planning authority applies stricter standards. They expect extensions to either match traditional styles closely or adopt high-quality contemporary design that complements the historic setting. Contemporary extensions can work well on older properties because they let people distinguish between original and new elements.
Your local planning authority examines whether your extension uses appropriate construction materials that match or complement existing buildings. They also check if your design follows specific local planning policies. Some councils set minimum distances between properties or limit extension heights in certain areas. You can find these requirements on the Planning Portal or your council's website.
Neighbour Impact and Consultation
The neighbour consultation scheme requires councils to notify properties adjacent to your site about your planning application. Planning officers carefully review any objections raised during this consultation period.
They assess three main impacts:
Loss of light: Does your extension block sunlight to neighbouring windows or gardens?
Privacy: Do new windows overlook previously private areas like bedrooms or gardens?
Outlook: Does your extension dominate neighbours' views where they previously saw open space?
Neighbour objections don't automatically mean refusal. Planning officers weigh the concerns against planning policies and the actual impact. A two-storey extension might face more scrutiny than a single-storey one because it typically affects neighbours more.
Your site plan must show distances to boundary lines and neighbouring properties. These measurements help planning officers evaluate potential impacts objectively.
Precedent and Previous Approvals
What worked for your neighbour won't automatically work for you. Each planning application receives individual assessment based on current policies and site-specific factors.
Planning officers consider whether similar extensions exist in your area, which can support your case. However, they also apply the latest planning policies, which may have changed since nearby extensions were approved.
Your property might face different constraints than neighbouring homes. Some houses have Article 4 directions removing permitted development rights. Previous planning conditions on your property could also restrict what you can build. The local planning authority reviews your property's planning history before making decisions.
Permitted Development Rights and Their Limits
Permitted development rights let you extend or alter your house without applying for planning permission, but strict size limits and conditions apply. Understanding when these rights exist, when they don't, and how to get legal confirmation matters more than many homeowners realise.
Criteria for Permitted Development
Single-storey rear extensions can extend up to 3 metres from the original rear wall for terraced houses or 4 metres for detached and semi-detached houses. Two-storey extensions are more restricted and must not extend beyond 3 metres from the original rear wall for any house type.
The height of your extension cannot exceed the highest part of your existing roof. The eaves height of any extension must not go above the eaves of your existing house.
All buildings within your curtilage, including extensions and outbuildings, cannot cover more than 50% of the total curtilage area. This excludes the original dwellinghouse but includes everything added since 1 July 1948.
Side extensions must not exceed half the width of the original house. No part of your extension can be forward of the principal elevation that faces the highway.
You'll need to check with your council whether Article 4 directions apply to your property. These directions remove permitted development rights in specific areas, meaning you'll need full planning permission even for works that would normally be permitted development.
Situations Where Permitted Development Does Not Apply
Permitted development rights do not apply to flats or maisonettes under any circumstances. If your house was created through change of use permitted development rights (Classes M, N, P, PA, or Q), you cannot use PD rights for extensions.
Properties in designated areas face additional restrictions. In conservation areas, National Parks, Areas of Outstanding Natural Beauty, or World Heritage Sites, you cannot build extensions beyond the rear wall or add cladding to walls without planning permission.
Listed buildings have no permitted development rights for alterations or extensions. You'll need both planning permission and listed building consent.
The Planning Portal confirms that if previous planning permissions removed your PD rights through planning conditions, you must apply for planning permission regardless of size. Some new housing developments automatically strip these rights to maintain uniformity.
Lawful Development Certificates
A lawful development certificate provides legal proof that your proposed work qualifies as permitted development. You apply to your local planning authority, which has eight weeks to decide.
The certificate protects you if the council later claims your work needed planning permission. It costs less than planning permission and involves less scrutiny, but the council checks your proposal against all permitted development rules.
You don't legally need this certificate before starting work. However, solicitors often request one during property sales to prove extensions were lawful. Without it, you may struggle to sell your property or face retrospective planning applications.
The application requires detailed drawings and measurements showing how your proposal meets every permitted development criterion. If the council refuses, you'll need to apply for full planning permission instead.
Key Planning Permission Rules for Different Types of Extensions
Different extension types face distinct planning rules based on their size, position, and impact on your property. Single-storey additions have more flexibility under permitted development rights, whilst two-storey extensions face stricter height limits and boundary requirements.
Single-Storey Extensions
Your single-storey extension can extend 4 metres from the rear wall if you own a detached house. Semi-detached and terraced properties are limited to 3 metres under standard permitted development rights.
The height restrictions cap your extension at 4 metres maximum. Your new structure cannot exceed the height of your existing house eaves.
You can extend further through the Larger Home Extension Scheme. Detached houses qualify for up to 8 metres, whilst semi-detached and terraced properties can reach 6 metres. This requires prior approval from your council and includes a neighbour consultation period of 42 days.
Side extensions must not be wider than half the width of your original house. They cannot exceed 4 metres in height. If your property sits on designated land, you need full householder planning permission for any side extension.
Two-Storey Extensions
Two-storey extensions face more restrictive rules than single-storey additions. Your extension cannot project more than 3 metres beyond the rear wall of your house.
You must maintain at least 7 metres between your extension and any boundary opposite the rear wall. This ensures adequate spacing and protects your neighbours' light and privacy.
Height limits prevent your extension from rising above the existing house eaves. The roof design must complement your current property.
All side extensions of more than one storey require householder planning permission. No permitted development rights apply to these structures. The total enlargement of your property, including the original house and all extensions, cannot cover more than 50% of your total curtilage.
Side and Rear Extensions
Side extensions on the principal elevation require planning permission in most cases. Your principal elevation is the front of your house that faces the main road or access point.
Rear extensions offer more flexibility under permitted development. You cannot extend beyond a wall that forms the principal elevation and fronts a highway.
The position relative to boundaries affects your options. Extensions within 2 metres of a boundary face additional height restrictions. Your extension cannot exceed 3 metres at the boundary point.
Materials and design influence approval chances. Councils expect extensions to use materials similar to your existing house. The design should match the character of your property and surrounding area.
Special Restrictions: Conservation Areas, Listed Buildings, and Sensitive Sites
Some properties face additional layers of control beyond standard planning rules. These restrictions protect historically or environmentally important locations, and they significantly limit what you can do without formal consent.
Conservation Areas and Areas of Outstanding Natural Beauty
Conservation areas cover over 10,000 designated zones across the UK where the character and appearance warrant protection. If your property sits within one, you'll need planning permission for work that would normally fall under permitted development rights.
This includes demolishing any building over 115 cubic metres, removing or altering gates, fences, walls, and railings visible from the road. You'll also need approval for certain roof alterations, cladding changes, and satellite dish installations on front or side elevations. Trees in conservation areas receive automatic protection, requiring notice before any work.
Areas of Outstanding Natural Beauty impose similar constraints. Councils scrutinise any development that might harm the landscape character. Extensions and alterations face stricter size limits, and materials must suit the local vernacular. The planning officer will assess visual impact more critically than in non-designated areas.
Sites of Special Scientific Interest add another layer of restrictions focused on protecting wildlife and geological features. Any work that might affect these designated sites requires consultation with Natural England before planning permission can be granted.
Listed Buildings and Listed Building Consent
Listed buildings require separate consent for any work affecting their character, whether internal or external. This applies even to minor changes like replacing windows, removing internal walls, or altering historic features.
The listing covers the entire structure and any buildings within its curtilage that predate 1948. Outbuildings, boundary walls, and garden structures often fall under the same protection. Your extension will need both planning permission and listed building consent.
Councils must consult Historic England on applications affecting Grade I and II* buildings. The decision-maker weighs the harm to heritage significance against the benefits of your proposal. Officers expect detailed heritage statements explaining how your design respects the building's character. Unauthorised work on listed buildings carries criminal penalties, including unlimited fines.
Article 4 Directions and Their Implications
Article 4 directions remove specific permitted development rights in defined areas. Councils use them to control development that would otherwise need no permission. Your local authority can impose them anywhere they consider additional control necessary.
These directions commonly restrict extensions, roof alterations, window replacements, and changes to external materials. Each direction specifies exactly which permitted development rights it removes. You must check with your local planning authority whether an Article 4 direction affects your property. The council's planning portal usually shows these designations on their constraints map.
Work that breaches an Article 4 direction requires planning permission. If you proceed without it, the council can serve an enforcement notice requiring you to undo the changes.
Building Regulations and Overlapping Legal Requirements
Planning permission focuses on whether you can build, but building regulations approval ensures your extension meets safety and construction standards. You'll also need to consider the Party Wall Act if your work affects shared boundaries with neighbours.
What Building Regulations Cover
Building regulations address the structural safety, fire protection, energy efficiency, ventilation, drainage, and accessibility of your extension. These rules apply to most extensions regardless of whether you need planning permission.
Your extension must comply with requirements for structural integrity, damp proofing, insulation, electrical work, and proper drainage connections. Building control will check that foundations are adequate, walls are properly constructed, and windows provide sufficient ventilation and emergency escape routes.
You'll need building regulations approval even for extensions built under permitted development rights. The regulations also cover modifications to existing structures, such as removing internal walls or adding new doorways. Some councils publish supplementary planning documents (SPDs) that provide additional guidance on local building standards and expectations.
Approved Inspectors and Building Control
You have two options for building regulations approval: your local authority's building control service or a private approved inspector. Both have the same legal authority to approve your work and issue completion certificates.
Local authority building control officers typically charge fees based on the project value and conduct inspections at key stages. Approved inspectors are private companies that compete for business and may offer more flexible inspection schedules.
You must notify building control before work begins. Inspections usually occur at foundation stage, damp proof course level, before covering drainage, and at completion. Your builder cannot proceed to the next stage without approval from the previous inspection.
Party Wall Act and Agreements
The Party Wall Act 1996 requires you to serve notice on adjoining property owners if your extension involves work on a shared wall, builds up to a boundary, or involves excavations within three to six metres of a neighbouring property.
You must provide a party wall notice at least two months before starting work. Your neighbour can either consent to the work or dissent, which triggers the appointment of party wall surveyors.
If disputes arise, each party appoints a surveyor (or agrees on a single agreed surveyor) to produce a party wall award. This document sets out how the work will proceed and what protections are required. You're responsible for all costs associated with the party wall process, including your neighbour's surveyor fees if they dissent.
Common Pitfalls and Practical Considerations
Many homeowners underestimate how local planning policies affect their extension projects, and they often submit applications without proper technical guidance. Understanding the specific rules that apply to your property, getting the right professional advice, and knowing what to expect in terms of costs and timelines can prevent costly delays and rejections.
Understanding Local Planning Rules
Your local council's planning policies determine what extensions are acceptable in your area. These policies change over time, so an extension approved three years ago might not meet current standards.
Supplementary Planning Documents (SPDs) provide detailed guidance on home extensions specific to your council. These documents explain what design features, materials, and sizes work best in your neighbourhood. Many homeowners skip reading these and submit applications that immediately clash with local expectations.
Conservation Areas and Listed Buildings face stricter requirements. If your property falls into these categories, you'll need to pay extra attention to materials, design details, and even internal changes. Green Belt properties also have significant limitations on extension sizes.
Article 4 Directions remove certain permitted development rights in specific areas. Your neighbour might have built an extension under permitted development, but if an Article 4 Direction now applies to your street, you'll need full planning permission instead.
Technical Guidance and Professional Advice
Technical mistakes account for many planning application rejections. Issues with overlooking, loss of light to neighbours, and incorrect measurements appear frequently in refused applications.
Prior approval applications apply to certain permitted development projects. You must submit details about how your extension affects neighbouring properties before starting work. This process is simpler than full planning permission but still requires accurate technical drawings.
Hiring an architect or planning consultant helps you understand what's possible on your site. They check your existing house's permitted development status, review any restrictions on your curtilage, and assess whether features like dormer windows or roof lights need permission.
Professional advisers also spot potential problems early. They can identify if your plans might cause overlooking issues or if the extension's size works within your property boundaries. This saves you from paying the planning application fee only to receive a rejection.
Costs, Timelines, and Application Process
The planning application fee varies by project type. A standard home extension costs £258 in England (as of 2025). Prior approval applications cost £116. These fees are non-refundable, even if your application gets rejected.
Full planning applications take eight weeks for a decision. Prior approval applications take six weeks. The council can request additional information during this time, which extends the timeline. Complex applications in Conservation Areas or involving Listed Buildings often take longer.
Extension costs go beyond the planning fee. You'll pay for professional drawings, structural calculations, and potentially specialist reports. Budget for these upfront costs before construction begins.
Your property's curtilage affects what counts as permitted development. Outbuildings and previous extensions use up your permitted development allowance. If you've already built a garage or garden room, this reduces what you can add without planning permission. Check what's been built before to understand your remaining allowances.
Frequently Asked Questions
Councils assess extensions based on how they fit the local area, affect neighbours, and meet current planning standards. Materials, size, parking impact, and environmental concerns all play distinct roles in their decision.
What are the key considerations a local council assesses for home extension applications?
Councils examine whether your extension matches the character of your street and neighbourhood. They check if the design, height, and overall appearance fits with surrounding properties.
Planning officers review your extension against current local and national planning policies. These policies change over time, so what was approved years ago might not meet today's standards.
The council also considers any site-specific restrictions. Conservation areas, listed buildings, and green belt locations all have stricter requirements that affect what you can build.
How does the impact on neighbours influence the council's decision on granting permission for extensions?
Your extension must not cause significant loss of light to neighbouring properties. Councils measure the impact using technical assessments that calculate how much natural light enters your neighbour's windows and garden areas.
Privacy is another major concern. The council checks if your extension creates new windows or elevated areas that overlook neighbouring homes or private outdoor spaces.
Councils also assess if your extension appears overbearing or dominant when viewed from neighbouring properties. An extension that feels too close or too large from a neighbour's perspective may face rejection.
Can you outline the importance of building materials and design in council assessments of extension projects?
Materials should match or complement your existing home. Councils prefer extensions that use similar brick, render, roofing tiles, and window styles to maintain visual consistency.
The design needs to respect local architectural patterns. If your street features specific design elements like pitched roofs or particular window proportions, your extension should follow these patterns.
In conservation areas, councils scrutinise materials and design details more carefully. You may need to use traditional materials and construction methods to preserve the area's historic character.
What role does the size and scale of the proposed extension play in the planning permission process?
Councils assess if your extension is proportionate to your original house. An extension that doubles the size of a small home often raises concerns about overdevelopment.
The council checks if your extension leaves adequate garden space. Most councils have policies requiring a reasonable amount of outdoor amenity space to remain after construction.
Height and depth measurements determine if your extension dominates neighbouring properties. Extensions that exceed specific dimensions may require planning permission even if smaller versions would be permitted development.
How do councils evaluate the effect of an extension on local traffic and parking?
Councils consider if your extension removes existing parking spaces from your property. If you're losing a garage or driveway space, you may need to demonstrate alternative parking arrangements.
The council assesses if your extension changes how many people will live in or use the property. Larger extensions that significantly increase occupancy can raise concerns about additional vehicles on the street.
In areas with existing parking problems, councils scrutinise any development that might worsen the situation. You may need to provide evidence that your extension won't add pressure to on-street parking.
In what ways do environmental and sustainability criteria factor into the council's review of extension planning permissions?
Councils expect new extensions to meet current building regulations for energy efficiency. Your plans should show proper insulation, efficient heating systems, and appropriate glazing specifications.
The impact on existing trees and landscaping matters to planning decisions. Protected trees require special consideration, and councils may refuse permission if your extension damages important green features.
Some councils require sustainable drainage solutions for extensions with large roof areas. You may need to include water management features that prevent increased flood risk to neighbouring properties.