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What is the difference between a roof window and a dormer window?

A roof window (or skylight) is fitted flush within the slope of a roof, while a dormer projects outward, creating additional headroom and floor space.  

Both can be installed under permitted development but must meet specific size and position limits to qualify.  

Also consider building regulations for a new dormer, find out more on Planning Portal  

Common Questions

Do I need planning permission to add air conditioning to my home?

Adding air conditioning to your home is considered permitted development provided all the limits and conditions set out in legislation are met. The limits set out the size, placement and quantity of air conditioning units allowed.

If your home is in a protected area such as a Conservation Area then permission will be required. If you live in a listed building then consent will be required.

The installation of air conditioning must comply with building regulations. It is advisable to contact an installer who can provide the necessary advice, preferably one who belongs to either the Microgeneration Certification Scheme or the relevant Competent Person Scheme.

For more information on air conditioning, read our heat pumps common project.

Is there a maximum height for a new dormer?

Yes, under permitted development, a new dormer must not be higher than the existing highest part of the roof. It should also have materials that are in similar appearance to the existing roof. Additional limits apply in conservation areas and on listed buildings. Read about planning permission for loft conversions on Planning Portal

Do I need planning permission to convert flats back into a house?

Deconversion is the process of restoring a previously subdivided house back to its original state as a single property. Merging flats to create a single house may require planning permission, so you should discuss proposals with your local planning authority before starting work.

Read more about converting flats back to a house.

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

Do I need permission for a satellite dish?

Under the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended), you have a general permission to install an antenna up to a specific size on property without the need for planning permission. This general permission depends on your house type and area. Your local planning authority can give you more advice.

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