Which statement about joist notching and holes is true?

Which statement about joist notching and holes is true?

• A. Notching on the edge of the joists shall not exceed one-fourth the joist depth.
• B. Notching shall not exceed one-half the joist depth.
• C. Holes bored in joists may be within 1 inch of top or bottom.
• D. Diameter of any hole may exceed one-third the depth.

Answer: (A)

When you modify a joist by notching or boring, you’re reducing the cross-section that carries bending and shear loads. Notches cut into the edge remove material from the area most critical for resisting bending, so the limit is kept tight to preserve strength. Limiting an edge notch to no more than one-quarter of the joist depth ensures there’s still enough wood to carry the load without compromising the joist’s stiffness and safety. Notches deeper than that weaken the joist too much and increase the risk of failure under load. Holes follow their own limits—up to one-third of the joist depth and kept away from the top and bottom faces (typically at least a couple of inches from each). Holes that are too large or too close to the edge would similarly reduce strength. So the statement that edge notches must not exceed one-quarter of the joist depth is the correct one because it correctly reflects the supported balance between removing material and maintaining structural capacity.

When you modify a joist by notching or boring, you’re reducing the cross-section that carries bending and shear loads. Notches cut into the edge remove material from the area most critical for resisting bending, so the limit is kept tight to preserve strength. Limiting an edge notch to no more than one-quarter of the joist depth ensures there’s still enough wood to carry the load without compromising the joist’s stiffness and safety. Notches deeper than that weaken the joist too much and increase the risk of failure under load. Holes follow their own limits—up to one-third of the joist depth and kept away from the top and bottom faces (typically at least a couple of inches from each). Holes that are too large or too close to the edge would similarly reduce strength. So the statement that edge notches must not exceed one-quarter of the joist depth is the correct one because it correctly reflects the supported balance between removing material and maintaining structural capacity.