One of the most common questions homeowners ask before starting a building project is whether they need planning permission for their house extension. The answer depends on several factors including the size, type, and location of your proposed extension.
What Is Planning Permission?
Planning permission is formal approval from your local council to carry out building work or change the use of a property. It exists to ensure that new developments are appropriate for their surroundings and comply with local planning policies. In England and Wales, the planning system is governed by the Town and Country Planning Act 1990.
Permitted Development Rights
Many house extensions fall under Permitted Development (PD) rights, which means you can build without needing to submit a formal planning application. However, PD rights come with strict limitations:
- Single-storey rear extensions: Up to 4 metres for detached houses, or 3 metres for semi-detached and terraced properties
- Prior Approval extensions: Up to 8 metres (detached) or 6 metres (other houses) but you must notify the council first
- Side extensions: Must be single storey, no wider than half the original house width, and no higher than 4 metres
- Two-storey extensions: Cannot extend beyond 3 metres from the rear wall and must be at least 7 metres from the rear boundary
When You Definitely Need Planning Permission
You will need to submit a full planning application if your extension:
- Exceeds the Permitted Development size limits
- Is on a listed building or in a conservation area
- Involves a flat, maisonette, or converted property
- Covers more than 50% of your garden area
- Is higher than the existing roofline
- Faces a highway and extends beyond the front building line
The Planning Application Process
If you do need planning permission, the process typically takes 8 weeks for a standard householder application. You will need professional architectural drawings including floor plans, elevations, site plans, and a design and access statement. At QM Designs, we prepare all the required documentation and can submit the application on your behalf.
Building Regulations Are Separate
Even if you do not need planning permission, you will almost certainly need Building Regulations approval. This ensures your extension meets structural safety, fire safety, energy efficiency, and accessibility standards. Building regulation drawings are more technically detailed than planning drawings and include construction specifications, insulation details, and structural calculations.
How QM Designs Can Help
We provide comprehensive architectural drawing packages for house extensions across the UK. Whether you need planning permission drawings, building regulation drawings, or both, our team delivers precise, council-ready plans. We offer free initial consultations and no-obligation quotes, with most projects completed within 7 to 14 working days.
Get your free quote today to discuss your extension project.