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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 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

Do I need building regulations approval or planning permission to change the roof on my conservatory?

Many homeowners choose to replace their traditional polycarbonate conservatory roof with a solid tiled roof for better thermal efficiency.

If the change significantly alters the structure or appearance of the roof, then planning permission may be required. Most alterations to roofs are considered permitted development, providing they meet the limits set out in legislation.

A new roof must comply with building regulations to ensure it is structurally safe, energy efficient and properly ventilated.

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.

I’m replacing a window, do I need planning permission or building control approval increase its size?

Increasing the size of a window will often fall under permitted development rights, meaning an application for planning permission is not required to make the change, provided limits and conditions are met.

Any new window must be of similar appearance to the original which you are replacing.

Permitted development rights do not apply to flats. To increase the size of a window in a flat or maisonette you will require planning permission.

 If you live in a listed building, you will require listed building consent for any major changes.

Where the work has as significant impact on the external appearance of the house, especially on the principal elevation, planning permission may be required.

Building control approval will likely be required where the change impacts the structure of a building, this primarily occurs when an opening Is widened. When altering walls you may want to consult a structural engineer.

Building control will also consider energy efficiency, glazing, ventilation and fire safety.

What permissions are required for a pond in my garden?

Most garden ponds will fall under permitted development rights, meaning an application for planning permission is not required. In planning terms a pond will be classed as an outbuilding, to read the full rules around installing an outbuilding, visit our common projects section.

For ponds which are particularly deep or large, you may need to apply for planning permission. If you are unsure, you should contact your local planning authority for advice.

In a listed building you will require listed building consent for any major changes.

When installing a pond, you should take into account other regulatory considerations such as environmental permits or any protected species which may be impacted. Further thought will have to be placed when creating ponds near riverways or in areas of flood risk.

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