Garage Conversion design

What the room has to do

Converting a garage is mostly about the door opening and the floor. The opening becomes a wall with a window, and the slab has to come up to the level and warmth of the rest of the house. Everything after that is a normal room in an unusually well-proportioned box.

Layout rules

• A single garage is typically 12×20ft — enough for a bedroom, office or gym, not for two of them.
• The slab usually sits 4in below house level; either ramp it or build the floor up and accept the ceiling loss.
• Fill the door opening with glazing wide enough to read as a window wall, not a patched hole.
• Keep the new wall on the same plane as the house facade, or the conversion is visible from the street forever.
• Allow 24in of depth for insulation and lining against the exterior walls.

Lighting plan

Garages have one dimension of daylight at best, so the new glazing does the heavy lifting and the artificial layer has to cover the back half properly. Wall-wash the rear wall — it is the surface furthest from the light and the one that decides whether the room feels deep or dim.

What usually goes wrong

• The old door opening filled with a single small window, so the room reads as a converted garage.
• The slab left cold, which no amount of flooring fixes.
• Ceiling height lost twice, to the floor build-up and to a new lining.
• No thought given to where the car and its contents now go.

In a small one

A single garage is exactly one good room. Splitting 12×20ft into a bedroom and an ensuite gives you two spaces that are both too small; leaving it as one gives you a room people actually use.