When there is no risk to health and safety, small detached buildings and extensions are usually exempt from building regulations. 

Extensions to buildings

The extension of a building at ground floor level having a floor area which does not exceed 30m2 by the addition of:

  • conservatory - 75% of the roof and 50% of the external walls are glazed with transparent materials and any doors between the existing dwelling and the new conservatory being maintained
  • porch - providing a covered approach to the entrance to a dwelling and the door between the existing dwelling and porch being maintained
  • covered yard or covered way
  • car port open on at least two sides
  • conservatories or porches are exempt only if the glazing they contain complies with Part K of the building regulations.

Small detached buildings

  • single storey building, having a floor area which does not exceed 15m2, which contains no sleeping accommodation, constructed of any material
  • single storey building having a floor area which does not exceed 30m2, containing no sleeping accommodation, and constructed substantially of non-combustible material, or sited at least 1m from the boundary of its curtilage
  • nuclear shelters under 30m2 floor area. Excavation for the shelter not to be nearer to other buildings than the depth of the excavation plus 1m.

Ancillary buildings

  • builders huts containing no sleeping accommodation
  • estate sales buildings
  • buildings other than dwellings or offices used in connection with a mine or quarry.

Greenhouses and agricultural buildings

  • greenhouses are only exempt providing they are not used for retailing, packing or exhibiting. Greenhouses used as a garden centre shop are not exempt.
  • agricultural buildings and buildings principally for keeping animals are exempt if they are not used as a dwelling, are at least one and a half times their height from any building where there is sleeping accommodation and have a fire exit not more than 30m from any point in a building.

Temporary buildings

Those which remain for less than 28 days.

Building not frequented by people

  • These are detached buildings into which persons do not normally go or only intermittently to inspect plant and machinery.
  • The exemption only applies if the building is sited at least one and a half times its height, either from the boundary or from the point on a building into which people normally go.

Building controlled under other legislation

  • buildings subject to the Explosives Acts.
  • buildings other than houses or offices erected on a site licensed under the Nuclear Installations Act.
  • buildings includes in the Schedule to Section 1 of the Ancient Monuments and Archaeological Areas Act.
  • certain buildings of statutory undertakers and other specified bodies.
  • crown property.