Foundations are required to carry and distribute the load of the building safely. Therefore, all buildings should have adequate foundations. The factors that need to be considered when designing a foundation are:

• Type of soil
• Adjacent structures
• Trees
• Drains and sewers
• Size and construction of the new building
• Ground condition
• Landfill sites

It is advisable to contact a structural engineer or speak to a building control body about plans for new foundations. 

Read more about foundations for extensions.

Your planning application must be made up of:

• The necessary plans of the site
• The required supporting documentation
• The completed form
• The correct fee.

The local planning authority will not be able to process your application unless the mandatory supporting documentation has been provided. You can also attach any other relevant documentation which you think will help the local authority determine the application.

What supporting documentation must be provided depends on the application type,  development type and local planning authority.

There are two levels of mandatory documents, national and local. If you’re applying online, the service will tell you what mandatory documentation you need to provide and allows you to attach the relevant documents. Most applications will require you to provide a location plan and a site plan.

In addition to the national list, your LPA may produce a list which details any specific documentation that is required to accompany the application. The requirements may vary according to the type of application, i.e. household, full, outline, etc. If you are applying online, this list is available from the supporting documents screen or your local planning authority’s website.

For more information around what to submit visit the how to apply section on Planning Portal.

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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If you carry out development without the necessary planning permission, and it doesn’t fall within permitted development rights, you may be in breach of the planning rules. In such cases, you will usually need to submit a retrospective planning application to seek approval for the work already completed or started. However, there is no guarantee that permission will be granted.  

Learn more about planning breaches on Planning Portal  

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Adding a storey on top of an extension will always require an application for planning permission.

If you want to add a storey on top of your house under permitted development rights, it must be on the principal part of the house.

If you want to add an additional storey on top of your house, it can be permitted development. It is only permitted development if it follows certain rules:

The current house

• Is not a building containing one or more flats, or a flat contained within such a building
• Was constructed between 1 July 1948 and 28 October 2018
• Has not already had additional storeys added to it
• Is not on Article 2(3) land or a site of special scientific interest
• Was not changed to be used as a house (from a previous non-residential use) under permitted development rights.

How many storeys can you add?

• If the house is one storey then one storey can be added
• If the house is two or more storeys then two storeys can be added

Where can the storeys be added?

• The additional storeys must be added to the principal part of the house. The principal part of the house is the main part of the house excluding any front, side or rear extension of a lower height (regardless of these being part of the original house or subsequent additions).
• Engineering operations must only include works within the existing curtilage of the house to strengthen existing walls and foundations

How high can it be?

• The house cannot exceed 18 metres in total height
• Each storey cannot add more than 3.5 metres to the total height
• If the house is not detached the total height cannot be more than 3.5 metres higher than the next highest building that the house is attached to, adjoins, or is in the same row as.
• The additional storeys must have an internal floor-to-ceiling height of no more than 3 metres, and no greater than the internal height of any existing storey within the principal part of the house.

What materials can be used?

The materials used must be of a similar appearance to those used in the construction of the exterior of the current house

Where can windows be placed?

Windows must not be placed in any wall or roof slope forming a side elevation of the house.

Following completion of development:

• The house must remain in use as a domestic residential property
• No visible support structures must remain on or attached to the exterior of the house
• The roof pitch of the principal part of the house must be the same as it was prior to the development.

 If any of the limits set out above are exceeded then an application for planning permission will be required. If you are unsure, you should contact your local planning authority.

Find contact details for your local planning authority.