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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 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.

Do I need building regulations approval to install a new inside toilet?

Work to refit a bathroom with new units and fittings does not generally require building regulations approval, although drainage or electrical works that form part of the refit may require approval under the building regulations.

If a bathroom is to be provided in a room where there wasn't one before, building regulations approval is likely to be required to ensure that the room will have adequate ventilation and drainage, and meet requirements with respect to structural stability, electrical and fire safety.

Can I install patio doors to the rear of my house where there is currently a single external door?

Installing patio doors at the rear of your house is likely to fall under permitted development rights, meaning an application for planning permission is not required, provided certain limits and conditions are met.

The doors should be of similar appearance to those previously used, if they are not then generally planning permission will be required.

If you live in a listed building, you will need listed building consent for any significant works.
If you live in a designated area such as a conservation area or national park, then additional restrictions may be in place.

If you are unsure whether the work falls within permitted development rights you can check with your local planning authority or submit a lawful development certificate to prove the change is lawful and prevent any future enforcement action.

What permission do I need to knock through adjoining properties?

Planning permission is not normally required to turn two properties into one by knocking through a party wall provided the changes are internal and do not impact the external appearance of the property.

You should check with your local planning authority that they agree, and there are not any previous planning changes or conditions which may have an impact.

Additional permissions may be required depending on the building’s history and their location. If the building is listed, an application for listed building consent will be required before any major changes are made to the dwellings.

The work will have to comply with building regulations, the focus will be on structural work and safety.

Read more about how building regulations apply to internal walls.

Do I need planning permission for a single storey extension?

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.

The limits and conditions for building an extension under permitted development rules are covered in our guidance on the Planning Portal, and there are other points to take into consideration.

Visit Planning Portal to find out more.

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