The minimum ceiling heights required in the code depends on whether or not the space can be considered habitable. So, let’s look at how the code applies to habitable and non-habitable spaces so we can take full advantage of what is allowed.
The code defines habitable space as a space in a building for living, sleeping, eating or cooking. It specifically excludes bathrooms, toilet rooms, closets, halls, storage or utility rooms and similar spaces from being considered as habitable spaces. Except for some specific cases with bathrooms, hallways and utility rooms, a space that is not habitable has no required ceiling height.
A room must have adequate area before it can be considered habitable space. Section R304.2 tells us a habitable space cannot have less than 70 square feet of floor area and cannot be less than 7’ in any horizontal dimension. A room smaller than 70 square feet or less than 7’ wide could not be used as a bedroom. However, it could be used as a bathroom, utility room or storage room.
The floor area of a habitable room with a sloped ceiling must have a head clearance of at least 7’ in 50% of the habitable area, and at no point be less than 5’ high. A space that has a floor area with less than a 5’ ceiling height cannot be considered habitable space and could not be considered part of the bedroom. The part of the space that has sufficient ceiling height and is at least 7’ wide could be used as a bedroom and does not have to be separated from the non-habitable area.
Non-habitable areas including hallways, bathrooms and laundry rooms must have at least 7’ of headroom. However, a bathroom is permitted to have a sloped ceiling as long as at least 25% of the ceiling is at least 7’ high, and when the area in front of toilets and lavatories is at least 6’-4” high, and the space in front of and over the tub or shower is at least 6’-4” high.
Beams and girders are allowed to project into the required headroom as long as they are spaced at least 4’ apart.
While buyers of new houses normally want higher ceilings than the minimum required by code, they might find bathrooms, closets or storage areas that can be tucked into shorter spaces part of the charm in the design. The allowed height reductions can be a great benefit when working with an existing space such as a second floor or basement remodel. A 7’ ceiling in a hallway or utility room can be useful for accommodating ductwork as a way to meet an energy code option for ducts being located inside the thermal barrier.