Home Improvement

Do You Need Planning Permission for a House Extension?

Almost the first question any homeowner seeking to expand their property should ask is “Do you need planning permission for an extension?”. The rules for planning permission for extension in the UK mean that when the planned work falls within the scope of ‘permitted development’, planning permission for extension will usually not be required.

In this article, Fantastic Services will explain the meaning and purpose of planning permission and the criteria for building legally without it. The subject of building regulations is also explored.

This article is for you if:

  • You’re considering building a house extension;
  • Want to ensure that you comply with the rules;
  • Need to know what sort of extensions you can build without planning permission.

What is Planning Permission?

Planning permission is official consent to do a certain piece of building work. Local councils have specialist departments to consider, accept or refuse planning applications. Broadly speaking the purpose of planning permission is to ensure that new buildings or changes to existing ones are in keeping with the character of the local area, won’t place a strain on existing infrastructure, and will not be a nuisance or an eyesore for neighbours.

Many building projects including most new constructions, major changes to existing buildings and changes to the use of a building require prior approval from the planning department. Failure to apply for planning permission when it’s needed could result in an ‘enforcement notice’ being served, forcing you to undo the work. It’s illegal to ignore an enforcement notice. You can appeal against one but this is more complex than making sure your work complies with the rules in the first place.

What size extension can you build without planning permission?

Size isn’t everything though it’s certainly a factor. Along with questions such as what size extension needs planning permission you also need to be aware of other forces that come into play. For example, previous extensions built after 1948 will already take up some of your permitted development allotment, reducing the size of extension you can build. There are also different rules for listed buildings and for houses built on ‘designated land’ which means things like conservation areas, national parks or areas of outstanding natural beauty. Your house or the area could also be covered by covenants restricting building and development.

Assuming that none of these restrictions applies to you, you can find answers to the question ‘what size extension can I build without planning permission?’ and learn more about other criteria for building an extension without planning consent in the list below:

You may also like:
Moving and Packing Tips
What Is Better – to Extend Your House or Move in 2024?

Rules for permitted development

  • The property you’re planning to extend must be a house – flats or maisonettes don’t have permitted development rights;
  • Total extension footprint must take up no more than half the land around the ‘original’ house, that’s as it was in 1948 or, if later, when it was built;
  • Extensions built under permitted development must be no taller than the highest part of the existing roof;
  • Balconies, verandas or raised platforms are not covered by permitted development regulations;
  • Materials used for extensions must be similar to those used for the existing house – (skilled architects can stretch this rule without breaking it);
  • Extensions to the front of the house do not fall within permitted development, you need planning permission – but there are exceptions for porches;
  • Extensions to the side of your property must be single-storey with a width of no more than half of the original house and a height of 4 metres or less;
  • If a single-storey side extension is within 2 metres of the land boundary wall the maximum height permitted is reduced to 3 meters;
  • Extensions to the side of the house must be no nearer to the highway than the current house wall and must not front onto it;
  • Single-storey extensions to the rear of a detached house must extend no more than 8 metres from the original house external wall;
  • One storey rear extensions between 4 and 8 metres can only be built after the council has implemented the Neighbour Consultation Scheme;
  • Single-storey rear extensions to semi-detached houses must extend no more than 3 metres without neighbours agreement, up to 6 meters with;
  • Double-storey rear extensions must extend no more than 3 metres from the house and be at least 7 meters from the rear property boundary wall;
  • The roof pitch of double-storey extensions should match the pitch of the original roof as closely as possible;
  • As with single-storey extensions, if the property is within 2 metres of a boundary wall the maximum eaves height is reduced to 3 metres.

Here you can find all the services the professional designers and architects can help you with!

When deciding whether the extension you’re considering can be built without planning permission remember that it has to comply with all the rules relating to its type. It’s always advisable to consult a legal representative and your local planning department because planning rules can change nationally or be subject to local constraints.

Consulting with your local planning department also gives you a chance to discuss building regulations requirements. And don’t worry, local planners aren’t generally nearly as scary as the myths would have you believe! But if the thought of dealing with bureaucracy makes your heart sink you can always call in an architect or construction professional who’ll attend to the paperwork as well as the building work.

All extensions require building regulations

Permitted development rules allow you to do quite a lot without planning permission, building regulations are a different matter. Building regulations and controls are about ensuring that a property is safe and meets satisfactory standards for human habitation and energy efficiency.

There are different building regulations for different aspects of an extension. Doors and windows must meet standards relating to safety, thermal efficiency, ventilation and means of escape. Many electrical installations have to meet approved standards to eliminate fire or electrocution risks and generally have to be completed by a registered competent person or checked by a registered certifier. And so on throughout the project, even when you don’t need planning permission your extension has to comply with a range of building regulations requirements.

Here are a few questions builders and architects are often asked about building regulations and the answers to them:

Do I need building regulations for a small extension?

Yes, size isn’t the issue, safely is.

Do I need building regulations for a garage?

Yes if it’s enclosed and attached to the house but no if it’s free-standing and less than 30m2.

Do I need building regulations for a conservatory?

No, providing it’s less than 30m2 floor area and meets a few other requirements.

Here are a few examples of works that are exempt from building regulations:

  • Detached single-storey buildings that are less than 30m2 floor area and at least 1 metre from any boundary;
  • An attached carport which is open on at least two sides;
  • Single storey detached buildings without sleeping accommodation;
  • Porches less than 30 m2 providing they’re separated from the house by an external type door.

Need a professional?

Rely on the services of professional designers and architects to plan your extension.

Add a valid postcode e.g. SE1 2TH
  • We’re certified:

Do you need professional help for your house extension project?

Fantastic Services can connect you with partners who’ll provide architectural services and help you with house extensions, loft conversions, outbuildings and other home improvements, architectural services and design projects. These professionals will ensure your construction work complies with all the legal requirements including planning permission and building regulations compliance. Learn more about the house extension service provided by our partners and if you decide to book with us, be sure all the needed paperwork surrounding the building will be acquired in time.


  • Many extensions can be built without planning permission providing they fall under the permitted development rules;
  • The rules combine, an extension has to conform to all of them in order to qualify – local restrictions may limit permitted development rules;
  • House extension projects that don’t require planning permission still have to conform to building regulations standards.

Disclaimer: Every piece of information here is meant for informational and educational purposes only. So please, do not use this as a definitive legal basis. Fantastic Services encourages you to seek authority professional counsel before you decide to act upon what you have read. For more information, check our disclaimer.


Have you extended your home – how has it improved your life? Or maybe you have a dream plan for a future project. Tell us about it in the comments section below.

Img Source: Shutterstock / FOTOGRIN

0 0 votes
Article Rating
Notify of
Inline Feedbacks
View all comments
Would love your thoughts, please comment.x