Notches on the ends of joists shall not exceed what percent of the joist depth?

Notches on the ends of joists shall not exceed what percent of the joist depth?

• A. 15
• B. 10 (1/10th)
• C. 33 (1/3 rd)
• D. 25 (1/4th)

Answer: (D)

Notching reduces the cross-sectional area of a joist, weakening its bending capacity. To keep enough wood remaining for the joist to carry loads and avoid splits or failures where it bears at supports, the code allows only a quarter of the joist depth to be removed in end notches. So the maximum notch depth is 25% of the joist depth (one-quarter). For instance, if a joist is 9 inches deep, you can notch up to 2.25 inches. Notches larger than this would compromise strength, while smaller notches are even more conservative but still within the allowed limit.

Notching reduces the cross-sectional area of a joist, weakening its bending capacity. To keep enough wood remaining for the joist to carry loads and avoid splits or failures where it bears at supports, the code allows only a quarter of the joist depth to be removed in end notches. So the maximum notch depth is 25% of the joist depth (one-quarter). For instance, if a joist is 9 inches deep, you can notch up to 2.25 inches. Notches larger than this would compromise strength, while smaller notches are even more conservative but still within the allowed limit.