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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

Do I need permission to brick up an external door?

Bricking up an external door is classified as permitted development, meaning an application for planning permission is not required to complete the works. You will need to ensure that any materials used are of a similar appearance to the existing exterior of the house.

If you live in a listed building, then you will require planning permission and listed building consent for the change. In this instance it is best practice to talk to your local planning authority.

Find your local planning authority.

Do I need planning permission to raise garden level?

Raising your garden level a small amount is likely to not require planning permission as it is likely to have minimal impact on the chances of flooding or overlooking your neighbours.

Increases of over 30cm may require planning permission as a significant change can impact drainage or your neighbours. If the changes are close to a boundary, you should consider whether it will overlook your neighbours or be intrusive.

You should contact your local planning authority to understand whether your proposed changes will require planning permission.

Do I need planning permission or building control approval to merge two flats into one?

Merging two flats into one, commonly known as amalgamation is likely to require planning permission as it will impact the local planning authorities housing supply. The council’s views on this will vary from council to council. It is recommended that you contact your local planning authority to understand their position.

If you do not need to apply for planning permission then you can apply for a lawful development certificate to prove that the change is lawful.

Building regulations will be required if there are physical works taking place as part of the amalgamation, this may include removing walls or changing electrics. Visit the relevant common projects on our site for more information.

Do I need planning permission to add a garden office?

Rules governing outbuildings apply to sheds, playhouses, greenhouses and garages as well as other ancillary garden buildings such as swimming pools, ponds, sauna cabins, kennels, enclosures (including tennis courts) and many other kinds of structures for a purpose incidental to the enjoyment of the dwellinghouse.

If you are unsure if your planned building falls into the category of 'outbuildings' or if you are unsure if planning permission is required, please contact your local planning authority.

Outbuildings are considered to be permitted development, not needing planning permission, subject certain limits and conditions.

Read about the limits and conditions for outbuildings

Browse our Outbuildings Mini Guide

Where can I find information about change of use class from C3 to C2?

An application for full planning permission for a change of use is often required when changing from a house (use class C3) to a residential institution (use class C2). This is due to the increased activity which a C2 use would have on the local street area through the addition of visitors, staff and changes to parking.

Read additional information on use classes and changes of use.

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