Converting a brick garage into a room

The short answer

Converting a brick garage means replacing the garage door with a new insulated wall and window, raising and insulating the floor, insulating the walls and ceiling, and adding heating, power and ventilation so the space meets Building Regulations for a habitable room. Because the walls are already masonry, the work is mostly about the door opening, the floor and keeping damp and cold out. Most integral and attached garages can be converted without planning permission, but check your house has no condition removing those rights.

The door infill

The big opening where the garage door was is filled with a new cavity wall: facing brick outside to match the house, block inside, insulation between. A window usually goes in the infill so the room gets daylight. The new wall needs its own foundation, and Building Control will want to see that it sits on something solid rather than the edge of the garage slab. Matching the brick well is what makes the conversion look original from the street.

The floor

Garage floors are usually lower than the house and have no insulation. The floor is raised to meet the house level, with a damp-proof membrane, insulation and a screed or timber deck on top. Getting the damp-proof membrane to link with the damp-proof course in the walls stops moisture rising at the edges.

Walls and damp

Many garages have single-skin brick walls, which are fine for a car but let cold and damp through for a room. These are usually lined on the inside with insulation and plasterboard, sometimes with a new inner block leaf. Any cracks or failed pointing on the outside should be repaired first, because a room will show damp that a garage hides.

Ceiling, roof and services

If there is a bedroom above, the ceiling needs fire protection and sound insulation. A flat garage roof may need re-covering and insulating. Heating, lighting, sockets and ventilation are added, and the room needs a safe escape route in case of fire. All of this is checked by Building Control before sign-off.

Detached brick garages

A detached garage can also become a room, such as a home office, gym or music room. The same principles apply, but it may need its own drainage and services run from the house, and planning rules differ for outbuildings. Our case studies include a garage extended to create a separate music practice room away from the house.

Things to decide first

Decide what the room is for, where you will park, and whether you want a door from the garage directly into the house. Check drains and meters inside the garage, because moving them affects the layout. With that decided, the builder can say whether it is a straightforward conversion or needs more structural work.

Ventilation, windows and light

A habitable room needs background ventilation and a window large enough to light it, and a ground-floor room off a hall or kitchen must have a safe way out in a fire. The new window in the infill is usually sized to line up with the house windows, which helps the frontage look planned. Trickle vents or a mechanical extract keep condensation down. If the garage is deep, a second window or a rooflight at the back can stop the far end feeling dark.

About us

D & A Brickwork & Building is a family-run firm based in Bidwell, Dunstable. We have more than 26 years of building experience, our bricklaying is NVQ Level 2 qualified, we are members of the Federation of Master Builders and we are fully insured. Estimates are free and follow a visit to see the job.

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