Technical guidance for building a domestic garage

For the purposes of the Building Regulations a definition of a domestic garage includes a carport and is either attached to, or detached from, the dwelling. It is generally recognised that a garage is an area designated for car storage.

Attached garages

Garages which are structurally connected to an existing house are classified as attached regardless of whether there is a doorway connecting them. Before building an attached garage you will need to submit an application to Building Control. Please refer to our user guide “Extending, Converting or Improving your Home” for guidance on how to make an application and the fee payable.

Detached garages

A detached garage is one which is structurally unconnected to a dwelling and is used for the storage of cars. An application is not required if the building is single storey, contains no sleeping accommodation and is less than 15m2 . If the building is in excess of 15m2 but less than 30m2 then an application will not be required if it contains no sleeping accommodation and is either:

  • constructed substantially of non-combustible material, or
  • greater than 1m from any boundary at any point.

If the detached garage has a floor area exceeding 30m2 then it is necessary to make an application to Building Control.


An application is not required if the proposed carport:

  • is situated at ground level,
  • has an internal floor area which does not exceed 30m2 or less than 1m from a boundary,
  • is open on at least two sides.

If the above criteria are not met then an application is required.

Complying with the regulations

Garages do not have to resist moisture penetration. Consequently, Building Control will not enforce the use of damp proof courses, membranes or other proprietary items for resisting rain penetration.

Like any other extension, a garage is required to have a proper drainage system for rainwater drainage.

Any part of a detached garage that is less than 1m from the boundary should be non-combustible.

An attached garage is treated in a similar fashion to an extension but:

  • not all the Regulations apply, depending on the intended use of the building.
  • in the interest of fire safety, if there is a door between a garage and the dwelling it should have 30 minutes fire resistance and be self closing. This opening must incorporate a step of at least 100mm between garage and dwelling floor.
  • the positioning of an attached garage must not affect the fire safety precautions of the existing house, e.g. must not jeopardise an escape window either on the ground floor or the first floor. If in doubt please contact us.
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