The maximum depth of a notch in the top or bottom of a floor joist is ______ of the depth of the joist.

The maximum depth of a notch in the top or bottom of a floor joist is ______ of the depth of the joist.

• A. 1/4
• B. 1/6
• C. 1/3
• D. 1/8

Answer: (B)

Notches weaken a joist where it carries bending stress, so framing rules limit how deep they can be cut. For a notch in the top or bottom face of a floor joist, the depth is restricted to one-sixth of the joist’s depth. This keeps enough material in the critical compression and tension zones to maintain safe carrying capacity. For example, a joist that’s 9 inches deep can have a notch no deeper than 1.5 inches. Notches deeper than that would noticeably reduce strength and aren’t permitted. The one-sixth limit is chosen because it balances the need for clearance with the joist’s ability to support loads.

Notches weaken a joist where it carries bending stress, so framing rules limit how deep they can be cut. For a notch in the top or bottom face of a floor joist, the depth is restricted to one-sixth of the joist’s depth. This keeps enough material in the critical compression and tension zones to maintain safe carrying capacity. For example, a joist that’s 9 inches deep can have a notch no deeper than 1.5 inches. Notches deeper than that would noticeably reduce strength and aren’t permitted. The one-sixth limit is chosen because it balances the need for clearance with the joist’s ability to support loads.