Do You Need Planning Permission for Your House Extension?

If you’ve been wondering if you can extend your home without planning permission, the short answer is yes: the solution’s called permitted development.

Permitted development rights are government guidelines that allow you to make changes to your property without going through an approval process.

Sound good? It is; avoiding a planning application can reduce your extension timeline and costs, not to mention being one less thing to think about. However, permitted development rules are very specific and do limit what you can do to your space. 

From single-storey extensions to loft conversions, here we break down the essential rules and key considerations of doing work to your home without planning permission, so you can make an informed decision. 

What is planning permission?

Planning permission is formal consent given by local authorities when homeowners want to make significant changes to their property. This legal requirement ensures that proposed developments meet local building standards, preserve the character of an area and comply with urban planning regulations.

Typically, major structural changes, significant extensions and alterations that totally change the look or architecture of a building need explicit approval from the local council.

Planning permission vs permitted development

While planning permission involves a detailed application process (typically you’ll have to provide site plans, architectural drawings, existing and proposed property measurements, material specifications and information on how your plans might impact your neighbours) permitted development offers a more streamlined approach. 

Permitted development rights allow homeowners to make certain improvements without submitting a full planning application. These changes are pre-approved by the government, providing a faster and often less expensive route to updating your home.

Understanding permitted development rights

The overall aim of permitted development is to simplify the home improvement process while protecting the characteristics of an area and its infrastructure. Permitted development allows you to expand your home and make minor external and structural changes within specific size and design restrictions. 

Permitted development rules vary depending on the property type, location and existing structures, but there are some elements that apply across the board: 

1. Permitted development rights only apply to houses. If you live in a flat or maisonette, you’ll have to get full planning permission
2. If your house is a listed building or in conservation area, area of outstanding natural beauty, or world heritage site, you’ll have very limited permissions, if any 
3. You can only extend your home via permitted development if it’s not been extended previously (dating back to 1948)

Detached houses in rural areas have more freedom under permitted development than terraced houses in a city as changes to these properties will have less impact on neighbours, and there’s more space to play with. Similarly, period homes are subject to stricter regulations than new builds, particularly regarding use of materials and protection of existing facades. 

Benefits to extending without planning permission

Extending your home through permitted development offers several advantages, potentially cutting costs and time, and offering a clear structure for your plans to adhere to.

Depending on what you want to do, the planning application process can be lengthy – typically you can expect to wait for up to three months to get an answer. If your plans get rejected or modifications are required, the timeline will inevitably be longer or you might have to start from scratch. If you get planning approval, you might also have site inspections from local authorities during the build. 

While planning applications are subject to a fee (calculated on the size of your plans), there’s no cost involved for permitted development, you can just get started. For some people, having clear and concrete permitted development rules to stick to for their extensions is a welcome structure to work to, for others, it can feel limiting. 

It’s worth noting that even if you don’t require planning permission you will probably still need approval from building regulations approval from your local council – these are guidelines to ensure that your new space meets safety and energy standards.

Types of extensions that don’t require planning permission

There’s a lot you can do to your home without getting planning permission. As long as you meet the conditions relevant to your property and area, you can add a single or double-storey extension, side extension, rear extension, porch extension, loft conversion or garage extension. Under permitted development you can also replace windows and rooflights, remove internal walls, and build outbuildings. 

Conditions to extend without planning permission in the UK

Single-storey extensions

Single-storey extensions can be completed without planning permission if they meet specific criteria:

• Maximum height of 4 metres
• Rear extensions limited to 3 metres (attached) or 4 metres (detached)
• Eaves height no more than 3 metres near boundaries
• Materials match the existing property
• No verandas, balconies or raised platforms
• Maintain at least 50% of the original garden area

Two-storey extensions

In addition to the requirements on the garden area and balconies, two-storey extensions must also adhere to the below rules:

• Be no taller than the existing building
• A minimum of 7 metres from rear boundaries
• Match the roof pitch and existing materials of the property

Front extensions

To add a front extension to your property without planning permission, it must:

• Match the existing property’s materials
• Avoid verandas, balconies or raised platforms
• Not extend beyond the principal elevation

Porch extensions

Porch extensions are permitted when:

• The ground area does not exceed 3 square metres
• The height does not exceed 3 metres
• It’s located more than 2 metres from a boundary adjacent to a main road

Rear extensions

Rear extensions follow similar rules to single-storey extensions and must:

• Have a total height of no more than 4 metres
• Not extend more than 3 metres (attached) or 4 metres (detached)
• Have an eaves height of no more than 3 metres if near a boundary
• Use materials that match the existing property
• Not include verandas, balconies, or raised platforms
• Not reduce the garden area below 50% of the original plot size

Side extensions

Side extensions are allowed when they:

• Are no wider than half the width of the original house
• Have a total height of no more than 4 metres
• Have an eaves height of no more than 3 metres if near a boundary
• Use materials that match the existing property
• Do not include verandas, balconies or raised platforms

Basement conversions

You can add a basement to your home without planning permission so long as:

• No significant changes are made to the external appearance of the property
• The property is not listed or located on designated land
• The conversion does not involve structural work that requires approval

Loft conversions

Loft conversions can be done without seeking formal approval so long as:

• The conversion does not exceed 40 cubic metres for terraced houses or 50 cubic metres for detached and semi-detached houses
• The roof enlargement does not exceed the existing roof height
• Dormer windows do not extend beyond the roof plane facing a main road
• The materials match the existing property
• The conversion does not include verandas, balconies or raised platforms

Garage conversions

For garage conversions, the rules are:

• The conversion does not alter the external appearance of the property significantly
• The work does not extend beyond the existing garage structure

To replace a window 

You can replace a window in your house whenever you like, so long as:

• The replacement matches the style of the existing windows
• The property is not listed or located on designated land
• The replacement does not alter the size of the opening

To knock down internal walls

If you’re looking to remove internal walls, you can do so freely if:

• The walls are not load-bearing (if they are, building regulations apply)
• The work does not impact the external structure of the property

For a rooflight

The permitted development rules for adding a rooflight to your original house are:

• The rooflight must not project more than 150mm from the roof plane
• The rooflight is not higher than the highest part of the roof
• The property is not listed or located on designated land

For a new fence or wall

You can construct and maintain your fence or wall under permitted development rights if:

• The height does not exceed 1 metre if adjacent to a main road, or 2 metres elsewhere
• The property is not listed or located on designated land

Outbuildings

A home extension with an outbuilding doesn’t require any local planning permission so long as:

• The height does not exceed 2.5 metres at the eaves and 4 metres overall with a pitched roof
• The outbuilding is not located forward of the principal elevation
• The building is used for ancillary purposes only

How to confirm if planning permission is needed

Firstly, is your property listed or in a conservation area? If the answer is yes, there’s a high chance you might need planning permission. Otherwise, precisely measure the dimensions of your desired extension and map out the materials you want to use – do they comply with the rules for your property type and area? Make sure to pay close attention to height and width specifications. Also look into any specific restrictions imposed by your local council that might impact your project. 

If you’re unsure if you need planning permission, it’s always best to get in touch with an architect or local planning authority to be 100% sure before you start work. While you can apply retrospectively for planning permission, if your plans are rejected then you’re legally bound to return your property to its original state, which would be a huge waste of money. 

How far can you extend without planning permission

Extension limits vary based on property type and location, but as a rule of thumb:

• Single-storey: 3-4 metres from original rear wall
• Two-storey: typically 7 metres from rear boundary
• Side extensions: up to half the original house width

Find a home renovation contractor with Thomas from The Page

Planning an extension doesn’t have to be overwhelming. At The Page, we specialise in matching homeowners with trusted, hands-on contractors who can bring visions to life at competitive prices – without sacrificing quality. We’ve already done the hard work of finding exceptional contractors: we team up with Pagers not just for their skills but their approach to project management and communication.

Ready to start your extension journey? Our renovation coaches understand both the practical and emotional aspects of extending your home, providing expert guidance at every step. We’ll help you understand the process, connect you with the right contractors for your extension, and ensure you feel confident and supported from start to finish.