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

Answer: (A)

Notches in joists weaken the member, especially near supports where bending stresses are high. To preserve enough cross-section and strength, end notches are limited to a specific portion of the joist depth. The standard limit is one-fourth of the joist depth, meaning you can notch up to 25% of the depth at the ends. For example, a 9-inch-deep joist can have a notch up to 2.25 inches deep. If you need a larger notch, you’d have to reinforce or adjust the framing. The other percentages would either be unnecessarily conservative or too large to maintain adequate strength.

Notches in joists weaken the member, especially near supports where bending stresses are high. To preserve enough cross-section and strength, end notches are limited to a specific portion of the joist depth. The standard limit is one-fourth of the joist depth, meaning you can notch up to 25% of the depth at the ends. For example, a 9-inch-deep joist can have a notch up to 2.25 inches deep. If you need a larger notch, you’d have to reinforce or adjust the framing. The other percentages would either be unnecessarily conservative or too large to maintain adequate strength.