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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

Do I need planning permission or building control approval for damp proofing of external walls?

Planning permission is unlikely to be required for the installation of external damp proofing unless the work will change the external appearance of the building or is part of a larger project.

If you live in a listed building you will need listed building consent for any significant changes, this can include external damp proofing. Additional rules may also apply if you live in a Conservation Area or other protected area.

Building regulations approval is not required for installing an external damp proof course (DPC).

Read further guidance on damp proofing.

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

Do I need planning or building control for covered outdoor kitchen?

If an outdoor kitchen is not a permanent structure, then planning permission will normally not be required.

Where planning permission is required, it may be granted through permitted development rights, provided it meets the limits set out in legislation. Most outdoor kitchens fall within the set limits unless they are particularly tall or close to a boundary.

While there is no specific permitted development right for ‘outdoor kitchens’ it may be classified as an ‘outbuilding’.

You can view the limitations for outbuildings and outdoor kitchens in the relevant common project

If the structure exceeds the limits set out through permitted development rights, then it will require an application for planning permission.

Different rules may apply if you live in a listed building or conservation area. If this is the case, you may wish to consult your local planning authority.

Read about the building regulations that cover outdoor kitchens.

What building regulations apply to the conservatory if I remove the door to make it open plan?

If the conservatory is not separated from the house by external quality walls, doors or windows, then it will lose its building regulations exempt status. As such it will be required to adhere to thermal efficiency rules and ventilation rules.

The new opening created from removal of the door will also need building regulations approval.

Find out more from our conservatories common project

Do I need planning permission to upgrade to double glazed windows?

For houses, replacing windows with double glazing usually doesn’t require planning permission, provided the style and appearance are similar to the original. However, if you live in a flat/maisonette, listed building, or a conservation area, planning permission or listed building consent may be required, especially if the changes affect the external appearance.

Read more about planning permission for windows and doors for houses

Read about planning permission for windows and doors for flats and maisonettes

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