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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.

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 summerhouses or garden offices need building regulations approval?

If you plan to put up a small, detached building like a garden shed, garden room, garden office, annexe or summerhouse (all classed as outbuildings), building regulations generally won’t apply if the building has a floor area under 15 square metres and does not include any sleeping accommodation.

For buildings with a floor area between 15 and 30 square metres, building regulations approval is usually not needed - as long as the building does not include sleeping accommodation and either:

  • it is at least one metre away from any boundary, or
  • it is built mainly from non-combustible materials.

Read more about the building regulations that apply to outbuildings.

Don't forget to check the permitted development rights for outbuildings.

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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.

How can I find out if permitted development rights have been removed in my area?

National planning regulations allow certain alterations to be made to a property without requiring planning permission; these are known as permitted development rights. In some cases, local authorities may remove or restrict these rights for specific types of development that would otherwise be allowed. This is achieved through the use of Article 4 Directions, which are intended to protect the character, heritage, and appearance of designated areas.

If your local planning authority has issued an Article 4 Direction, some of your permitted development rights may no longer apply. As a result, you may need to submit a planning application for works that would not normally require one.

You can check whether an Article 4 Direction affects your property by visiting your local authority’s website.

Do I need planning permission to erect a veranda?

Verandas will often require planning permission as they do not fall under permitted development rights. If the veranda is raised over 0.3 metres, covers more than 50% of the land around your house, is on the principal elevation or on a roof then it will need planning permission.

You may require additional consents if you live in a Conservation Area or listed building. If you are unsure, you should contact your local planning authority.

For more information about planning permission for verandas and balconies, read our common project.

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