Maximum notch depth in solid lumber joists?

Maximum notch depth in solid lumber joists?

• A. One-sixth the joist depth
• B. One-half the joist depth
• C. One-quarter the joist depth
• D. One-eighth the joist depth

Answer: (A)

Notching a solid lumber joist reduces the carrying section and weakens its bending capacity. To protect structural strength, the maximum notch depth is limited to one-sixth of the joist depth. This keeps enough wood in the outer fibers, which are most stressed under loading, so the joist can still bend and support weight safely. In practice, notches are typically allowed in the middle third of the joist depth, but only up to that one-sixth limit. For example, if a joist is 8 inches deep, the notch should not exceed about 1.33 inches. The other options would remove more material than the standard limit allows, so one-sixth of the depth is the correct maximum.

Notching a solid lumber joist reduces the carrying section and weakens its bending capacity. To protect structural strength, the maximum notch depth is limited to one-sixth of the joist depth. This keeps enough wood in the outer fibers, which are most stressed under loading, so the joist can still bend and support weight safely. In practice, notches are typically allowed in the middle third of the joist depth, but only up to that one-sixth limit. For example, if a joist is 8 inches deep, the notch should not exceed about 1.33 inches. The other options would remove more material than the standard limit allows, so one-sixth of the depth is the correct maximum.