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How to Get Planning Permission for a Home Extension in the UK

30th May 2025

Planning a home extension in the UK means understanding how planning permission works and the rules that apply to domestic building projects. This guide outlines the key steps and requirements for anyone looking to expand their home legally and smoothly.

Understanding Planning Permission for House Extensions

Planning permission is the formal approval needed from your local planning authority (LPA) for specific types of building work. Many home extensions fall under what’s known as permitted development rights, which means you may not need to apply. However, these rights have strict limitations.

You can check if your project is allowed under these rights using the official Planning Portal guidance on extensions.

Permitted Development Rights: What They Cover

Some extensions can go ahead without planning permission, provided they meet all permitted development criteria:

  • Size Limits: For a detached house, a single-storey rear extension can extend up to 8 metres. For other homes, the limit is 6 metres.

  • Height Restrictions: Must not be taller than the existing roof or over 4 metres high.

  • Land Use: You can’t build on more than half the area of land surrounding the house.

  • Appearance: Materials should be similar to those of the existing house.

Permitted development doesn’t apply to flats or to properties in certain areas like conservation zones or national parks.

Close-up of a construction permit and blueprint plans with a stylish black and gold pen, ideal for construction projects.

When Planning Permission Is Required

You’ll need planning permission for your house extension if:

  • The size or height exceeds the permitted development rules

  • Your property is located in a conservation area or other protected location

  • The house is listed or near a listed building

  • You’re adding balconies, verandas, or other raised platforms

These situations mean submitting a formal application. To understand what to expect, the GOV.UK guide to planning permission is a useful reference.

The Planning Application Process

If your extension requires permission, here’s how the process works:

  1. Consult Your LPA: Getting pre-application advice can help shape your proposal and avoid common pitfalls.

  2. Prepare Plans and Documents: These include drawings, site plans, and a design statement.

  3. Submit Your Application: Use the Planning Portal or your local council’s website.

  4. Wait for Review: Most decisions take around eight weeks.

  5. Get a Decision: You’ll receive written confirmation once a decision is made.

If the application is refused, you can appeal or revise and resubmit. The FMB offers a helpful overview on what typically requires planning permission and how to stay compliant.

Don’t Forget Building Regulations

Planning permission is separate from building regulations approval. Even if you don’t need permission, your extension will still need to meet structural and safety standards.

Inspections during and after construction will ensure the work is compliant. This includes things like insulation, electrics, drainage, and overall safety.

How Western Building Consultants Can Help

Planning an extension can get complicated quickly. Western Building Consultants are here to help manage the entire process, including:

  • Initial Design Work: Practical, clear, and within regulations

  • Planning Applications: We take care of submissions, tracking and communication with the LPA

  • Building Regulation Drawings and Support: Ensuring your project is safe, legal and buildable

You can also access reliable advice from professionals like the Royal Town Planning Institute (RTPI), especially if your property has restrictions or heritage status.

A close up view on the hand and arm of a building inspector filling in a form, standing on a staircase checking for home defects and environmental qualities.

Conclusion

Staying informed about home extension rules in the UK is the first step to a successful build. Understanding when you need planning permission and how to go about the planning application process makes the project smoother and avoids costly setbacks.

To get expert support, from drawings to permissions, speak to Western Building Consultants today – we’re here to help you get it right from day one.

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