The room measures 8 feet by 8 feet with full required ceiling height throughout, and it has a door, a closet and a compliant escape and rescue window. What is the correct call on the size of this room?
- It fails, because a habitable room must have a floor area of not less than 70 square feet
- BIt passes, because the room exceeds the 7-foot minimum horizontal dimension in both directions
The 7-foot horizontal dimension is a second, separate requirement. Passing it does not cure a floor area that is below the minimum.
- CIt fails, because a room used for sleeping must have a floor area of not less than 100 square feet
One hundred square feet is not a code minimum for a sleeping room in the IRC. It is a figure that comes from rental housing standards and local ordinances.
- DIt passes, because minimum area applies to the dwelling as a whole rather than to individual rooms
Minimum area is applied room by room to each habitable room, not to the dwelling as an aggregate.
Why A is correct
Eight feet by 8 feet is 64 square feet, and the minimum floor area for a habitable room is 70 square feet. The separate requirement for a minimum horizontal dimension of 7 feet is satisfied, but area and dimension are independent tests and the room fails on area. Kitchens are excepted from the minimum area requirement, and a bedroom is not.
What this question is testing
The item tests whether the candidate applies minimum floor area and minimum horizontal dimension as separate tests and can compute a simple room area under field conditions.
On the job
Attic and basement conversions produce most of these, because the usable footprint is whatever the framing left behind. The owner has usually already put a bed in the room and is offended by the finding. The practical resolution is often to combine the space with an adjoining area, or to permit it as a study or storage room, which changes nothing about how the owner will use it but does change what the code requires of the escape opening and the ceiling height.
Memory technique
Seventy and seven. One is the floor, the other is the narrowest wall.
Exam tip
Seventy square feet of area and 7 feet in any direction. Two numbers, both required.
Where to look it up
IRC Chapter 3, Section R304 for minimum room areas, with the kitchen exception noted there.