What Size Extension Can I Build Without Planning Permission?

Understanding Permitted Development Rights and Class A of the GPDO

Permitted development rights allow homeowners to make certain improvements to their property without submitting a full planning application. Class A of the GPDO specifically covers the enlargement, improvement, or alteration of a dwelling house.

However, these rights come with conditions and limitations. 

• They may be restricted for properties in conservation areas, world heritage sites, national parks, SSSIs or areas of outstanding natural beauty. 
• A separate consent would be required if the property is a listed building. 
• They do not apply to flats or maisonettes.
• A local council can remove permitted development rights with Article 4 Directions.

To ensure your extension complies, you may need to review the specifics of your property. For tailored advice, explore our Feasibility Studies service.

What Can You Build Without Planning Permission?

For professional advice on planning matters, visit Adapt Planning’s Permitted Development page. Whether you are considering single-storey rear extensions, loft conversions, or other types of home improvement projects, understanding the intricacies of planning approval and permitted development rights is crucial.

Our expert team can guide you through the process, ensuring compliance with local authority regulations and maximizing your property’s potential. From initial feasibility studies to securing necessary approvals, we provide comprehensive support tailored to your specific needs.

Single-Storey Rear Extensions

Under Class A, single-storey rear extensions are one of the most popular types of home improvement projects. Here are the main guidelines:

• Depth Limits:
  • Up to 4 metres for detached houses.
  • Up to 3 metres for semi-detached or terraced houses.
  • Larger extensions are possible (up to 8 metres for detached houses and 6 metres for others) under the Neighbour Consultation Scheme.
• Height Restrictions:
  • Maximum height of 4 metres.
  • Eaves height must not exceed the eaves of the existing house.
• Other Considerations:
  • Extensions cannot cover more than 50% of the land surrounding the original house.
  • Materials should match the existing property.

Two-Storey Rear Extensions

Two-storey rear extensions are also allowed under permitted development, but stricter rules apply if the project is more than one storey:

• Depth Limits:
  • Maximum of 3 metres for all property types.
• Height and Placement:
  • The extension cannot be taller than the original house.
  • A minimum distance of 7 metres must be maintained from the rear boundary.
• Design Considerations:
  • Materials must be similar to the existing property.
  • Roof pitch should match the original house.

Extensions that exceed these limits will require planning permission. If you need help determining feasibility, check out our Feasibility Studies service.

Side Extensions

Side extensions under Class A are limited to single-storey additions. Here are the key rules:

• Width and Height Limits:
  • Maximum width of half the width of the original house.
  • Maximum height of 4 metres.
• Placement Restrictions:
  • Extensions facing a highway are not permitted.
• Other Considerations:
  • The 50% curtilage rule applies.
  • Materials should match the existing house to maintain aesthetic consistency.

For advice on designing side extensions, consider our Permitted Development page.