According to the "Building Code of Australia" a Habitable Room is:
" a room used for normal domestic activities and
Includes a bedroom, living room, lounge room, music room, television room, kitchen, dining room, sewing room, study, playroom, family room, home theatre, and sunroom, but
Excludes a bathroom, laundry, water closet, pantry, walk-in wardrobe, corridor, hallway, lobby, photographic darkroom, clothes drying room, and other spaces of a specialised nature occupied neither frequently nor for extended periods."
Building Code Ceiling Heights
A room or space within a building must have sufficient height suitable for the intended function of that room or space. The requirement is satisfied if the ceiling height is not less than -
In a class 1, 2 or 3 building a habitable room excluding a kitchen - 2400mm - (2.4 meters) & in a kitchen, laundry or the like - 2100 mm (2.1 meters) and in a corridor, passageway or the like 2100mm (2.1 meters)."
According to BCA Vol 2 part 3.8.2, ceiling heights must not be less than:
- in a habitable room excluding a kitchen - 2.4 m and
- in a kitchen - 2.1m and
- in a corridor or passageway etc - 2.1m and
- in a bathroom, shower room, laundry, sanitary compartment, pantry, storeroom, garage, car parking area etc - 2.1m and
- in an attic, room with a sloping ceiling or projection below ceiling line or non-habitable room or similar - a height that does not unduly interfere with the proper functioning of the room or space. More than 50% of the ceiling space should be on average a minimum height.
- in a stairway - 2.0m measured vertically above the nosing line.
Otherwise, the room would be deemed to be a "utility room".
Technically the height is measured from the finished floor covering to underside of ceiling or lowest protrusion of the ceiling. If you are trying to determine whether you can build-in an area - ensure you take into consideration what you are going to put on the floor.
If there is any doubt about a ceiling height - you should speak to your local council: