Question 17
Domain 2: Building Planning, Means of Egress, and Safety ProvisionsWhat is the maximum projection of nosings beyond the tread face on residential stairs per the IRC?
Correct answer: A
Explanation
The IRC limits stair nosings on residential stairs to a projection of "3/4 inch minimum to 1-1/4 inches maximum" beyond the tread face. This range controls the overhang so the nosing is neither too short nor too long, matching the code requirement for safe, uniform stair geometry.
Why each option is right or wrong
A. 3/4 inch minimum to 1-1/4 inches maximum
IRC Section R311.7.5.3 governs stair nosings in residential construction and requires the nosing projection to be not less than 3/4 inch and not more than 1 1/4 inches measured horizontally from the leading edge of the tread. Because the question asks for the maximum projection beyond the tread face, the controlling upper limit is 1 1/4 inches, with the code also requiring the minimum 3/4-inch projection for compliance.
B. 1 inch minimum to 2 inches maximum
C. 1/2 inch minimum to 1 inch maximum
D. Nosings are optional on residential stairs