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What size extension can I build without planning permission?

In many circumstances, rules known as ‘permitted development’ rights allow you to extend a house without needing to apply for planning permission, providing specific limitations and conditions are met. If you want to exceed these limits and conditions, then it is likely that an application for householder planning permission will be required.

You can find information about the limits and conditions, prior approval and the building regulations on the Planning Portal by using the links below.  

Read about planning permission for extensions

Read about prior approval for larger single storey extensions

Find out about building regulations for an extension

Common Questions

What is the process for applying for planning permission?

When you, or an agent acting on your behalf, have submitted a planning application, the local authority will firstly check the application to check if it’s complete. This validation process allows the authority to ensure everything that is required to decide an application has been received and provided correctly. They will contact you if they require any further information from you.

After the application has been validated, the determination process begins and takes up to 8 weeks for smaller applications, or up to 13 weeks for larger applications. The authority should be able to give you an idea about the likely timetable. The local authority will contact you with their decision.

Read more about the decision-making process for planning applications.

What are permitted development volume limits?

To qualify as permitted development some household building work projects – notably extending a house – must not exceed limits to the volume being added.  

In England, the volume allowance mostly applies to loft conversions. You can read more on the Planning Portal. 

Use the volume calculator to find out the volume of several loft conversion and extension types.

Do you need planning permission to install an outside flue?

Fitting, altering or replacing an external flue, chimney, or soil and vent pipe is normally considered to be permitted development, not requiring an application for planning permission, providing certain conditions are met.

Read about the conditions which must be met to comply with permitted development rules.

Building regulations apply to installing a flue, and installation should be carried out by a suitably qualified installer.

Read about building regulations for flue installation.

How can I find out if my land is in a green belt?

The green belt is a specially designated area of countryside protected from most forms of development. It is protected to help stop urban sprawl, preserve the character of existing settlements and encourage development within existing built-up areas.

The government are working on improving access to public land records, allowing you to check certain restrictions on land. You can view their progress here and see whether your land is greenbelt (note: this tool is currently under development).

You should contact your local planning authority to find out if your land is in a green belt area, and any policies or restrictions that may apply as a result.

Do I need planning permission or building control approval for damp proofing of external walls?

Planning permission is unlikely to be required for the installation of external damp proofing unless the work will change the external appearance of the building or is part of a larger project.

If you live in a listed building you will need listed building consent for any significant changes, this can include external damp proofing. Additional rules may also apply if you live in a Conservation Area or other protected area.

Building regulations approval is not required for installing an external damp proof course (DPC).

Read further guidance on damp proofing.

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