Converting an integral or attached garage into a habitable room is one of the most cost-effective ways to create extra living space in a house. Because the structure already exists, the work is primarily about converting the existing space rather than building new fabric, which reduces the cost and complexity compared with a ground floor extension. However, the process is not without regulatory requirements and it is worth understanding them before you begin.
In terms of planning permission, the conversion of an attached or integral garage to habitable use is usually permitted development for a house, meaning you do not need to apply for planning permission. This is the case where the conversion does not extend the building beyond its existing footprint and the external appearance is not significantly changed. However, there are important exceptions. Properties in conservation areas, areas of outstanding natural beauty, or those with Article Four directions removing permitted development rights may require planning permission. Some planning conditions on the original house may also require the garage to remain as parking, in which case permission to change its use would be needed.
Building regulations approval is always required for a garage conversion to habitable use, regardless of whether planning permission is needed. The regulations cover several aspects of the conversion. The floor of a garage is typically at a lower level than the house and may not have the same damp proof membrane. The regulations require the floor to be built up to the level of the house with an appropriate damp proof course and insulation below. The garage door opening must be filled in with an insulated wall and window or door to provide adequate thermal performance. The existing roof may need insulation upgrades to meet Part L requirements. Fire safety, ventilation, and natural lighting must also comply.
The conversion of a detached garage is slightly more complex from a planning perspective. In some circumstances the change of use of a detached garage to a separate dwelling or an outbuilding used for habitation may require planning permission and could be subject to conditions around parking provision.
RCB Design and Build carries out garage conversions as part of our wider refurbishment and extension service across London. We manage the planning assessment, building regulations submissions, structural requirements, and fit-out to deliver a completed habitable space.