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Will I need building regulations approval for my outbuilding?

Will I need building regulations approval for my outbuilding?

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What is an outbuilding?

It could be any of these structures…

  • shed
  • carport open on two sides
  • greenhouse that isn't used for retail, packing or exhibiting
  • summer house
  • annex
  • garden enclosure for swimming pools, hot tubs and sauna cabins (see this information regarding swimming pools and consider whether yours will be classed as indoors or outside)
  • summerhouse
  • Garage
  • a garden room, garden office or garden studio
  • covered pergola
  • other small single storey building

You won’t normally need building control approval for most of these 'small detached buildings' (as they’re referred to in the building regulations) if they fit into either of the following categories:

Small detached buildings

  1. The floor area is less than 15 square metres and there is no sleeping accommodation.

  2. The floor area is between 15 and 30 square metres, with no sleeping accommodation, and the building is at least one metre from any boundary or is made substantially of non-combustible materials.

However, if there are electrics in any of these structures, these must comply with Part P (England and Wales) of the building regulations and, with increasing numbers of garden offices now featuring a shower or toilet, the plumbing, drainage and water supply these aspects will need to be built to meet the standards, as the extension of any existing drainage system to serve the exempt detached building, in which case the extended drainage must comply with these Parts of the regulations:

  • H1 - Foul drains
  • H2 - Wastewater treatment and cesspools
  • H3 - Rainwater drainage

If your outbuilding project doesn't fit the above descriptions – for instance if it’s going to be habitable accommodation like an annexe, an apartment for an elderly relative, or used as a utility room you'll need to make a building regulations application.

Further information

Every building project has its own unique requirements so always make sure you seek professional advice before getting started on the construction work.

Interested in building a garage, conservatory or swimming pool? Visit the relevant pages on this website:

Building regulations for garages

Building regulations for conservatories

Building regulations for swimming pools