Q: Are windows required in all basements?
A: Victor Staley, a building official in the town of Brewster, Mass., responds: The IRC’s definition of a basement is based on ceiling height, and the code regulates minimum ceiling heights, including those in basements. Section R305 states that the minimum ceiling height in habitable spaces (including habitable basements) shall not be less than 7 feet.
That same section goes on to state that basements that are not habitable shall not be less than 6 feet 8 inches in height. I take this to mean that if the overall below-grade ceiling height is less than 6 feet 8 inches, the space would not be considered a basement but rather a crawlspace. (I’ll address crawlspaces later.) The situation can get a little nuanced and complicated when a builder is looking at building out a habitable space in an existing basement, but I’ll leave that topic for another discussion.
As to the window requirement, if the house is being built with a basement that meets the ceiling height requirement, the code does require egress that meets IRC Section R310.1, whether the basement will be habitable or not. This section requires that the egress from these areas go directly to the exterior of the building through either a walkout door, a window, or a bulkhead.
The interior stairway between the basement and the first floor does not meet the requirement for egress to the exterior because it does not lead directly to the exterior of the building. So oddly enough, you could build a house with a basement, and the typical interior stairs would not be required, but an egress from the basement directly to the exterior would always be required.
This type of egress in section R310.1 is referred to as an Emergency Escape and Rescue Opening, or EERO. The EERO can be located anywhere along the basement wall, even if the space is mixed-use with part habitable and part uninhabited areas of the basement. The exception to this rule is when a room is designated as a bedroom. In that case, an EERO has to be placed in that bedroom so people trying to flee the bedroom do not have to go through another room to access an EERO. This EERO provision is attached to all bedrooms regardless of the floor on which they are located.
For a below-grade EERO, the code sets forth a minimum net opening area of 5 square feet. If a below-grade window is being used to satisfy the EERO requirement, section R310.2 also requires a window well that projects at least 3 feet from the house. The horizontal area of the window well must be at least 9 square feet.
As mentioned before, a below-grade space with less than 6 feet 8 inches of height would be considered a crawlspace and would not require an EERO. However, the code does require ventilation openings in these spaces.
