Extending your home can be an excellent way to add space and value without moving. The good news is that many house extensions fall under permitted development, meaning they do not require planning permission. However, there are specific rules and exceptions to be aware of. In this guide, we’ll break down the key points about permitted development rights for house extensions.
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Do You Need Planning Permission for an Extension?
For many homeowners, planning permission is not necessary when extending their property, provided that the project meets certain criteria. Under current regulations, single-storey rear extensions can extend up to 3 metres for semi-detached/terraced houses and up to 4 metres for detached houses without requiring planning permission. Extensions beyond these limits, up to 6 metres for semi-detached/terraced houses and 8 metres for detached houses, fall under the ‘Larger Home Extension’ category and require a Prior Approval application involving neighbour consultation.
It’s worth noting the exemptions that apply. For example, if your home has already been extended since 1948, that previous extension will count toward your permitted development allowance. Additionally, permitted development rights only apply to houses—not flats or maisonettes. If your property is in a Conservation Area, National Park, or similar protected zone, your rights may be restricted or removed entirely under an Article 4 Direction. Always check with your local council to confirm your permitted development status.
Permitted Development Rules for Extensions
Single-Storey Rear Extensions
- Extend up to three metres (four for detached houses). Or up to six (eight for detached houses) with a Prior Approval application.
- Materials must be similar to the existing house.
- The extension must not be taller than the existing house.
- It cannot take up more than 50% of the original garden space.
- The maximum height is four metres (or three metres if within two metres of a boundary).
- No balconies, verandas, or raised platforms are permitted.
Double-Storey Rear Extensions
- Extend up to three metres. Be within seven metres of rear boundary.
- The eaves and pitch must not be higher than the original house.
- If within two metres of a boundary, the maximum eaves height is three metres.
- The roof pitch should match the original house as closely as possible.
- Windows on the upper floor must be obscured glazing and non-opening (unless at least 1.7m above floor level).
- Two-storey side and front extensions are not permitted development.
Permitted Development vs. Prior Approval: Larger Home Extensions
As mentioned above, the Neighbour Consultation Scheme comes into play for larger home extensions that fall under permitted development but exceed certain size limits. This allows neighbouring properties to be informed about your extension and gives them the chance to object if they have concerns. The key distinction here is that larger single-storey extensions – those extending beyond three metres for terraced houses or four metres for detached homes, require Prior Approval under the Larger Home Extension Scheme.
This process involves submitting an application that notifies neighbours, and the local authority will assess whether any objections are reasonable and whether the extension will have an unacceptable impact on the amenity of neighbouring properties. If no issues arise, your extension can proceed without the need for full planning permission.
Neighbour Consultation Scheme Process
This scheme gives neighbours the opportunity to raise concerns about the extension’s impact, especially if the extension exceeds the set size limits. The council will assess whether the extension meets the local planning policies and whether it negatively impacts the neighbours, such as causing loss of privacy, light, or affecting the visual amenity of the surrounding area.
Side Return Extensions
Side return extensions are popular for Victorian terraced homes, reclaiming unused outdoor space to enlarge kitchens and living areas. Side extensions under permitted development must:
- Be no wider than half the width of the original house.
- Not exceed 4 metres in height.
- Maintain a maximum eaves height of three metres if within two metres of a boundary.
- If it’s classed as a ‘Larger Home Extension’, of more than 3 metres, or 4 metres for detached house, you will need to submit a Larger Extension Prior Approval application (see above).
Wraparound Extensions
Wraparound extensions combine a rear and side extension, forming an L-shape. Unfortunately, wraparound extensions typically do not qualify for permitted development. The main issue is that side extensions are limited to half the width of the house under permitted development rules. This means most wraparound projects will require a full planning application.
Basement Extensions
Basement extensions do not typically qualify for permitted development and will almost always require planning permission. This is due to the complex nature of digging below ground level and potential issues such as drainage, structural integrity, and local infrastructure.
Can Neighbours Object to a Permitted Development Extension?
Technically, neighbours can raise concerns, but their objections will not stop the project if the extension fully complies with permitted development guidelines. However, larger single-storey extensions (beyond three metres for a terraced house or four metres for a detached home) will require a prior approval application. This process gives neighbours the chance to voice objections, and the council may refuse approval if the extension significantly impacts them (e.g., blocking light or privacy concerns). Find out if a neighbour could stop your house extension here.
The Importance of a Certificate of Lawful Development
Even if your extension falls within permitted development rules, obtaining a Certificate of Lawful Development is advisable. This document provides proof that the work was legally carried out, which can be useful when selling your home in the future. Without it, buyers may hesitate, and mortgage lenders might require additional legal assurances.
Roof Alterations & Loft Conversions
In addition to traditional house extensions, you may consider roof alterations or a loft conversion. These types of work generally fall under permitted development, but they come with specific rules, such as limits on the volume of the extension and dormer window restrictions. If you’re planning to alter your roofline, it’s essential to check if your plans adhere to these regulations.
Outbuildings & Ancillary Structures
Outbuildings, such as sheds, garages, and garden rooms, must follow the same 50% garden coverage rule as house extensions. This ensures that the total coverage (including any outbuildings) does not exceed half the garden space of the original house. These structures must also comply with height restrictions, typically not exceeding 2.5 metres if located within 2 metres of a boundary.
Listed Buildings & Article 4 Restrictions
If your property is a listed building, or it falls under an Article 4 Direction, your permitted development rights may be restricted beyond the usual rules. Listed buildings often have more stringent regulations, and in some cases, any extension may require full planning permission, regardless of size (as well as Listed Building Consent).
Building Regulations Compliance
Even if your extension doesn’t require planning permission, building regulations approval is still necessary for structural work, electrical changes, plumbing, insulation, and drainage. It’s important to ensure your project meets these technical standards to ensure safety and compliance with the law.
What’s Changing? Permitted development in 2025
As of 2025, some changes to Permitted Development rules are possible. The Permitted Development Rights (Extension) Bill has been introduced to establish new allowances for home extensions and alterations. While still under consideration, this bill could impact existing regulations. Additionally, the UK government has been consulting on amendments to provide greater flexibility for homeowners, particularly regarding home enlargements, roof alterations, and incidental building construction. Homeowners should stay informed about any legislative updates and consult their local planning authority before proceeding with an extension.
Finding your extension architect
It’s important for you to have a basic understanding of whether you need permission for a side return extension, but the most critical thing is that you find the right architect to guide you through these legal requirements alongside the design decision-making process.
Here at Design for Me, we can match you with the perfect architect for your side return extension. Choose up to three interested design professionals for an initial consultation. And it’s all completely free!
- Quickly see who’s interested in your job.
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