How Much, How High to be Habitable?
Ceiling heights and the square footage of rooms are two of the measurements the 2006 International Residential Code considers as indicators of habitable space. The IRC defines habitable space as a space in a building for living, sleeping, eating, or cooking. Bathrooms, toilet rooms, closets, halls, storage or utility spaces and similar areas are not considered habitable spaces. Because occupants spend more time in habitable spaces than accessory areas, there are more regulations covering them. The code frequently calls for different requirements based on whether or not the space is habitable; therefore, it is important to be able to determine if it is.
For a room to be considered habitable, several requirements must be met. The minimum size requirements are that at least one room must be at least 120 square feet in size within a unit or house. All other habitable rooms must be at least 70 square feet in size.
The exception to this is the kitchen, which is only required to be a minimum of 50 square feet in size. Does this mean that a bathroom now has to be a minimum of 70 square feet? No, since the bathroom is not considered a habitable space, there is no minimum size requirement.
In addition to the requirement that a habitable room be a minimum of 70-square-feet in size, it must also be a minimum of 7 feet in any horizontal direction.
Additionally, minimum ceiling height requirements apply to habitable rooms, hallways, corridors, bathrooms, toilet rooms, laundry rooms and basements. The minimum ceiling height is 7 feet. This is a change from what you may have been used to in the Uniform Building Code, which had a minimum ceiling height of 7'6". The required height is measured from finished floor to lowest projection of the ceiling, with some exceptions.
Not more than 50 percent of the required floor area of a room is permitted to have a sloped ceiling less than 7 feet, with no portion of the required area less than 5 feet in height. What this is saying is if the room is required to have 70 square feet in area to meet the minimum habitable space requirement, then not more than 35 square-feet of the room can have a sloped ceiling less than 7 feet in height. Any portion of the room with a ceiling height of 5 feet or less will not contribute to the square footage requirement for the room. Beams and girders spaced not less than 4 feet on center may not project more than 6 inches below the required ceiling height. Ceilings in basements without habitable spaces may project within 6 feet 8 inches to the finished floor, and beams, girders, ducts, etc. may project to within 6 feet 4 inches of finished floor.
This discussion is based on current model codes. Some jurisdictions use older model codes and/or make amendments that modify specific requirements. Check with your local enforcement authority for more information. This article is based on Section R305 of the 2006 International Residential Code.
As the diagram above illustrates, any area with a ceiling height of less than 5 feet cannot contribute to a room’s habitable space requirements (shaded red). Additionally, not more than 50 percent of the required floor area of a room or space is permitted to be less than 7 feet in height (shaded orange). For example, in a 70-square-foot bedroom not more than half, or 35 square feet, could be between 5 and 7 feet in height in order for the room to be considered habitable.
This diagram shows a basement without habitable space. The minimum height is 6 feet 8 inches. However, beams, ducts and other structural components may project to within 6 feet 4 inches of the floor. It is important to understand that this basement is considered uninhabitable. In other words, it is just a deep crawl space and cannot be converted into bedrooms or a family room since it does not meet the requirements of a habitable space.
Correction of Code Changes For Egress from the June ASHI Reporter
ASHI Certified Inspector Daniel Keogh, Peach Inspections, Phoenixville, Pa., pointed out, “In the 2006 IRC R310, the word habitable has been removed and now all basements over 200 square feet must have egress.”