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Do You Need Planning Permission For An Extension?

Diving into a home extension brings a flurry of decisions, with planning permission sitting at the top. Our essential guide simplifies this vital step. It’s packed with insights on the instances where Permitted Development Rights apply and when it’s time to file for permission.

Outside of a modern extension

Posted on

November 7, 2023


Whether you envision a cosy extra bedroom or a sprawling open-plan living area, clarity on legalities is a must. Stick with us as we explore the ins and outs of adhering to UK planning laws, helping you to ensure your home improvement journey is as smooth as possible.

Do you need planning permission for an extension? (Updated for 2023)

In the UK, not every extension to a property requires planning permission due to “Permitted Development Rights.” These rights enable homeowners to undertake certain types of building works without the need for formal approval as long as they adhere to specific guidelines regarding dimensions, position, and the property’s context. 

However, these guidelines vary significantly, especially when dealing with properties in conservation areas or listed buildings. It’s imperative to consult with your local planning authority to confirm whether your project complies with the current regulations, as these can be intricate. 

When you do need planning permission for an extension

Planning permission becomes necessary for an extension in the UK under several circumstances that fall outside Permitted Development Rights. Key triggers requiring permission include:

Scale: If the proposed extension covers more than 50% of the original house’s surrounding land as of its original construction date or from July 1, 1948.

Height restrictions: When the peak of the extension exceeds the height of the existing house’s roof.

Aesthetic consistency: Utilising materials that don’t match the current structure or proposing a design that clashes with the local vibe necessitates permission.

Rear extension limits: Extensions of more than three metres in depth for terraced or semi-detached homes or four metres for detached homes.

Protected areas: Building within a designated land area—such as conservation zones, AONBs, and World Heritage Sites—often requires planning permission.

Historical considerations: Alterations to listed buildings always require additional consent.

Proximity to boundaries: For two-storey extensions, there’s a required seven-metre gap from the rear boundary.

Frontage: Any extension that sits in front of the main or side elevation facing the road.

Additional structures: Erecting conservatories, verandas, or balconies with specific size exceedances.

Previous extensions: Homes already extended under Permitted Development Rights may not have further rights for additional expansion.

To navigate these requirements, seeking advice from the local planning authority or a planning consultant is advisable, ensuring any extension project aligns with current planning policies.

How much does planning permission for an extension cost?

The expense of securing planning permission for an extension can vary based on your project’s specifics and your local council’s pricing structure. Here’s a general outline of the costs you might expect in England:

  • Standard residential extensions: For typical homeowner projects, such as adding a new single or double-storey extension, the fee is around £206. This figure is a general guideline for England, with separate scales applicable in Wales, Scotland, and Northern Ireland.

  • Complex developments: The fees escalate for more extensive construction endeavours, calculated on a per-square-metre basis.

  • Specialised applications: Extra fees may apply for proposals affecting conservation areas or involving listed buildings due to the additional considerations required.

  • Preliminary consultations: Some local councils charge for pre-application consultations, which can provide valuable insights into the feasibility of your proposal before you make a formal application.

It’s crucial to verify the latest fee schedule from your local council’s planning department or their website to get accurate and up-to-date pricing. This approach ensures that your budgeting for the planning process is as precise as possible.

What to do if you don’t have planning permission for your extension

If you discover that your extension lacks the necessary planning permission, here’s a structured approach to managing the situation:

Initiate dialogue with the local planning authority

Reach out to the local authorities to ascertain possible remedial measures. Open and transparent communication can be pivotal in resolving such issues.

Submit a retrospective planning application

You may apply for planning permission after the fact. If your extension closely aligns with what is typically allowed, you could receive approval post-construction.

Apply for a certificate of lawfulness

Should your extension have been in place for several years—four for building extensions and ten for changes in use—you might be eligible to apply for this certificate, which legally recognises your build as compliant with planning regulations.

Adhere to enforcement actions

In the event the planning authority deems the extension unacceptable, they may issue an enforcement notice demanding modification or removal of the structure. It is crucial to address this notice promptly, as ignoring it can lead to legal consequences.

Appeal decisions when necessary

If your late application is denied or you receive an enforcement notice, you retain the right to appeal the decision. Bear in mind that appeals can be lengthy, and there is no assured outcome.

Dismantle the extension if required

As a last resort, if your retrospective application and subsequent appeal do not succeed, dismantling the unauthorised extension may be the only option.

In such a scenario, seeking expert advice is advisable. A planning consultant or legal advisor with expertise in planning laws can provide tailored assistance. They can help negotiate with the planning department and advise on the feasibility of securing retrospective permission or succeeding in an appeal.


Do I need planning permission for a single-storey extension?

Determining the necessity for planning permission for a single-storey extension in the UK hinges on specific criteria. Under the rules of Permitted Development Rights, you’re typically allowed to proceed if your plans fall within these guidelines:

  • Projections: A single-storey rear extension can protrude up to four metres from the original rear wall for a detached property or up to three metres for other home types.

  • Maximum height: The extension’s height should not surpass four metres.

  • Proximity to boundaries: If the extension is within two metres of a boundary, the eaves height limit is three metres.

  • Consistency in appearance: The construction materials must be in keeping with the existing house.

  • Special areas: On designated land, such as national parks or conservation areas, additional restrictions usually apply.

  • Highway consideration: Side extensions on properties that would be directly facing a highway are generally not covered by Permitted Development Rights.

What are the consequences of extending without the necessary planning permission?

You risk enforcement action, which can compel you to revert your property to its original state. Applying for planning permission after the fact is an option, but approval isn’t guaranteed.

What size extension is permissible without planning permission?

Generally, single-storey rear extensions can extend up to four metres for detached homes and three metres for other home types without needing planning permission, subject to Permitted Development rules.

What is the expected timeframe to obtain planning permission?

Decision times for householder applications are approximately eight weeks, though more complex proposals may take longer to process.

Are planning permission and building regulations approval the same?

No, they’re not. Planning permission focuses on how the development looks and how it uses the land, whereas building regulations are about the technical details of construction.

What is the validity period for planning permission?

Planning permission is typically valid for three years from the date of issue. Construction must commence within this period, or the permission becomes void.

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