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What do I need to know about new foundations for an extension?

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.

Common Questions

What documents to I need to make a planning application?

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.

Do I need planning permission to add a small wooden canopy over my front door?

Adding a porch canopy is classed as permitted development provided it meets the limits and conditions set out in legislation. Where this is the case, no application for planning permission is required.

Porches must meet the following limits:

  • the ground floor area (measured externally) would not exceed three square metres.
  • no part would be more than three metres aboveground level (height needs to be measured in the same way as for a house extension).
  • no part of the porch would be within two metres of any boundary of the dwellinghouse and the highway.

Read our mini guide for additional information on installing a porch.

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What is a habitable room?

There is no single legal definition of "habitable room", as its use and meaning are subject to context. Generally, a habitable room is a space in a building that is designed for people to live, sleep, or spend extended periods of time in, but does not include bath or toilet facilities, corridors or utility rooms.

What are use classes and change of use?

Categorising land and buildings according to their type and purpose is known as Use Classes.  

A 'Change of use' can be within the same Use Class or from one Use Class to another.

You will need planning permission for certain changes to the use of a property such as changing from a residential use to a business use. However, it is possible to change use between some classes without having to make an application for planning permission.

Depending on the specifics of any proposed change of use, including any building work associated with the proposal, an application for planning permission or prior approval may be required.

Do I need permission to create an opening for a new window?

Inserting new windows which look similar to those previously used in the house will often not require planning permission. Some rules apply to new additions, for example if they are on an upper-floor side elevation they must be obscure glazed and non-opening or more than 1.7 metres above the floor.

Installing a new bay window on the front elevation would require planning permission as it is classed as a forward extension.

If you live in a listed building or conservation area you should contact your local planning authority.

 Any new openings will have to comply with building regulations, this may impact thermal heat loss, structure, ventilation and fire safety.

You can use a member of a competent person scheme to complete any work, this will ensure that the work is completed in-line with regulations.

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