Question 4
Domain 4: Wall Construction, Framing, and Exterior CoveringsPer the IRC, what is the minimum grade of lumber allowed for studs in load-bearing walls?
Correct answer: C
Explanation
The IRC permits studs in load-bearing walls to be framed with lumber of "No. 3 or stud grade," which is the minimum grade allowed for that use. This grade requirement ensures the member has sufficient structural capacity for wall loads.
Why each option is right or wrong
A. No. 1
B. No. 2
C. No. 3 or stud grade
IRC Section R602.3.1 requires studs in load-bearing walls to be a minimum of No. 3 grade lumber or stud grade, with the grade determined under the grading rules referenced by the code. The provision is specific to wall framing members carrying roof, floor, or other imposed loads, so lower grades are not permitted for that application.
D. Utility grade