Garage Conversion


The conversion of a garage into a living space is treated as a change of use of part of a building.

An application for approval under the Building Regulations must be made before the work commences. The submission of a Building Notice is an appropriate way to achieve this.


The following points must be considered when converting a garage into a living space -


a) Foundations

A foundation must be provided to carry any additional masonry loads such as a new inner leaf to external wall or the garage door infill. The condition and suitability of the existing foundation/floor can be checked when the door infill area is excavated.


b) Wall Thickness

If the existing wall is single leaf construction with piers, it must be checked for stability and freedom from defects. If satisfactory it is likely the wall would be considered suitable subject to c) and d) below


c) Weather Resistance

A wall of single leaf construction must be treated to provide satisfactory resistance to the passage of moisture. A weatherproofing compound applied on the internal face and incorporated into a floor membrane may be an effective way of achieving this. Alternatively an insulated timber stud partition or masonry wall may be suitable.


Floors (new and existing) should also have a suitable damp proof membrane. Cross flow ventilation may also be required to the roof.


d) Insulation

It may be necessary to insulate the floor, walls and roof to habitable standards, as follows;-

  • Floor Insulation U-value 0.25W/m²K
  • Wall Insulation U-value 0.3W/m²K (or cavity wall insulation 0.55W/m²K)
  • Roof Insulation U-value 0.18W/m²K at rafters or 0.16W/²K at ceiling level
  • Windows should achieve a U-value of 1.6W/²K

e) Ventilation

Windows must incorporate openable vents of an area equal to 1/20th of the floor area of the room, trickle vents to provide background ventilation of 8000mm². Mechanical extract ventilation may be required depending on the use of the proposed room. Ventilation may also be required to the roof.


f) Inner Room – Means of escape requirements

In an inner room situation (where the only escape is through the outer room) an escape window may need to be provided, with a minimum opening light of 450mm x 750mm and a smoke detector to give early warning.


g) Electrical Works

Depending on the use of the room, Building Regulations may be applicable to the electrical installation.


Download a printable PDF version of this Garage Conversion Guidance.




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