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How high can I build a single-storey extension without planning permission?

A single storey rear extension can fall under permitted development, meaning planning permission may not be required providing it meets certain criteria.  

In terms of height, the extension must:

  • Be no taller than four metres at its highest point
  • Have eaves no higher than the eaves of the original house
  • Not exceed the height of the original dwelling  

Read about planning permission for extensions on Planning Portal

Common Questions

Do I need planning permission or building control approval to install a new external door into my house?

The addition of a new external doorway will often fall under permitted development rights, meaning an application for planning permission is not required. This applies where the new doors are of similar appearance to those used elsewhere on the original building.

Permission may be required if your property is listed, you live in a conservation area oran Article 4 direction is in place. In these circumstances it is best to contact your local planning authority for more advice.

New external doorways which create a new or widened opening must comply with building regulations. A new structural opening will require a building regulations application.

The installation of a new door can be completed by a 'competent person' to ensure building regulation requirements are met. For more information on the competent person scheme and to find a registered person, visit the GOV.uk website.
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.

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

Can I use an outbuilding as a home office?

Yes, in most cases you can use an outbuilding as a home office without needing planning permission. As long as the use remains incidental to the main dwelling it is still considered part of your domestic residential use.

Read more about outbuildings

What are the planning and building rules for constructing a soakaway?

A soakaway does not normally require an application for planning permission provided it deals with surface water and does not discharge into a public sewer. Additional regulations may apply if you are in a conservation area or within the boundary of a listed building.

Building regulations will apply to the creation of a soakaway. The soakaway must comply with Part H of the building regulations which specifies where they can be located and the size that is permitted.

Read more about Approved Document H.

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