Planning consent or permitted development for house extensions explained

One of the first questions we get asked when visiting a client's house is: does the proposed extension require planning consent?

This article will explain which consent is required for your extension.

1. Permitted development

Certain extensions will fall under permitted development which means that planning consent is NOT required. We do advise clients however to apply for a Certificate of Lawful Development which is a very useful document to have when selling the house.
There is a strict set of rules of what counts as permitted development:

• Side extensions (which are 50% or less of the width of the house, with a maximum height of 4m) are permitted development, but NOT in conservation areas
• Extensions must not exceed 50% of the original floor area
• No front extensions 
• External materials must be similar in appearance to the existing house (which means if your house is rendered the proposed extension should be rendered too)
• If extensions are within 2m of the boundary the maximum height should not exceed 3m.
• Extension must not exceed 3m (attached houses) or 4m (detached houses) from the rear of the original house
• Single storey rear extensions must not exceed 4m in height

For more information on permitted development refer to http://www.planningportal.gov.uk/permission/commonprojects/extensions/miniguide OR http://www.planningportal.gov.uk/permission/house

The certificate of lawful development application can be submitted online on the planning portal and costs £86.

2. Prior approval Notification

Outside designated land (such as conservation areas) the size limit of extensions has been increased to 6m (attached houses) and 8m (detached house) until 30th May 2019. This approval is however subject to the neighbour consulting scheme. That means that the approval will only be issued if the adjacent neighbours do not object (they don't necessary have to consent, just not object).

This approval is subject to the same rules as the standard permitted development. It is important to note that the proposed development has to be entirely on the applicants land and party wall can't be shared between adjoining owners. This can sometimes cause issues if the neighbour has build an extension incorporating a poor quality garden wall. This garden wall will have to remain and be incorporated into the design which can cause construction problems.

The prior approval notification has to be submitted to the development team of the local authority by email and is free of charge.

3. Planning Approval

If the extension is larger than 3m (attached houses) or 4m (detached houses) from the rear of the original house AND is in a conservation area or the neighbour has subjected to the prior approval notification planning consent will be required.

What is considered acceptable depends largely on the individual planning officer, the local authority policies, and other local guidelines. As a rule of thumb planning will normally be granted for extensions which extend no more than 3.5m from the rear of the existing house. If the existing extension of your terraced house is for example 4.5 long you might not always be able to create an infill extension of the same length. It is therefore important to explore layout options how to incorporate the planning requirements yet create a functional and aesthetic scheme.

Householder planning applications can be submitted online on the planning portal and costs £172 planning fee.

4. Listed buildings

Any extensions to a listed building will require planning and listed building consent.