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Technical guidance - garage conversions

What you should consider when undertaking a domestic garage conversion

Garage conversions

When converting a garage to a habitable room an application to our building control department will be required. The submission of a building notice is an appropriate way to achieve this.

Basic requirements

When converting a garage to a habitable room, you should consider:

1. Foundations

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

2. Wall thickness

If the existing wall is of single layer construction with anything attached, it must be checked for stability and free from defects.

3. Weather resistance

A wall of single layer construction must be treated to provide satisfactory resistance to the passage of moisture. The provision of an inner layer to create a cavity wall will require a cavity tray at the base of the wall. Floors (new and existing) should also have a suitable damp proof membrane.

4. Insulation

It may be necessary to insulate the walls and roof to habitable standards. Walls should achieve a value of 0.3W/m2K. Windows should achieve a value of 1.6W/m2K (for example upvc double glazing with a 16mm argon filled gap and low-e glass). Roof should achieve 0.16W/m2K.

5. Ventilation

Windows must incorporate openable vents of an area equal to 1/20th of the floor area of the room and trickle vents to provide background ventilation of 8000mm2. If the room can only be accessed via another room the window will be required to have a clear opening size of 0.33m2 with a minimum dimension of 450mm in each direction, for escape purposes.

Please note that individual circumstances vary, please contact our building control department to discuss your individual requirements.