CSLB General Building (B)Mechanical, Electrical, Plumbing CoordinationMedium
A framer notches a 2x6 bearing wall stud to install a plumbing supply line. The stud is 5.5 inches wide. Per code, what is the maximum allowable notch depth in this bearing wall stud?
- A1.65 inches (30%)
- B0.55 inches (10%)
- C1.375 inches (25%)
- D2.75 inches (50%)
Show answer & explanationAnswer & explanation
Correct answer: C. 1.375 inches (25%)
For bearing walls, code limits stud notching to 25% of the stud width; 25% of 5.5 inches equals 1.375 inches. Exceeding this depth compromises the structural capacity of the bearing wall.
Why the other options are wrong
- A. 30% exceeds the bearing wall limit and would require engineering approval.
- B. 10% is overly conservative and not the code-specified maximum.
- D. 50% is the limit for non-bearing walls, not bearing walls.
Stud Notching Limits
Building codes restrict how deep a stud may be notched or bored to run plumbing or electrical lines without weakening the wall.
- Bearing wall studs: max 25% notch depth
- Non-bearing wall studs: max 40% notch depth
- Bored holes generally limited to 40% (bearing) or 60% (non-bearing) of stud width
Memory trick: Bearing walls get a quarter, non-bearing gets closer to half.