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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 planning permission to run an Airbnb or bed and breakfast?

Planning permission is not required if the home will be used as a short-term let for 90 days or less throughout the year.

If you plan on using the home as a short-term let for more than this time period, then you will need to apply for planning permission for a change of use.

If you rent a room in your property while you still live there, you will not require planning permission.

Do I need planning permission or building control approval to install a new external door into my house?

The addition of a new external doorway will often fall under permitted development rights, meaning an application for planning permission is not required. This applies where the new doors are of similar appearance to those used elsewhere on the original building.

Permission may be required if your property is listed, you live in a conservation area oran Article 4 direction is in place. In these circumstances it is best to contact your local planning authority for more advice.

New external doorways which create a new or widened opening must comply with building regulations. A new structural opening will require a building regulations application.

The installation of a new door can be completed by a 'competent person' to ensure building regulation requirements are met. For more information on the competent person scheme and to find a registered person, visit the GOV.uk website.
Can I change my house into a shared house for students (HMO)?

In many cases, yes. Converting a single residential property (Class C3) into a small House in Multiple Occupation (HMO) for up to six occupants can often be done under permitted development rights, specifically under Class L. This means that planning permission isn’t usually required.

However, if your property is located in an area covered by an Article 4 Direction, permitted development rights are removed, and you would need to apply for full planning permission to change the use from C3 (dwellinghouse) to C4 (HMO).  

Read more information about use class changes on Planning Portal

What is the difference between a roof window and a dormer window?

A roof window (or skylight) is fitted flush within the slope of a roof, while a dormer projects outward, creating additional headroom and floor space.  

Both can be installed under permitted development but must meet specific size and position limits to qualify.  

Also consider building regulations for a new dormer, find out more on Planning Portal  

What is permitted development?

Permitted development rights allow certain types of work to be carried out without the need to apply for planning permission. It typically covers things like small extensions, loft conversions and outbuildings, provided they meet specific size and location limits. These rights can vary or be removed in areas like conservation zones and by Article 4’s, so it’s best to check before proceeding.  

Read about permitted development and Article 4 directions on Planning Portal

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