Holes and Notches

While cutting into a load-bearing member should be avoided, there are times when it may be necessary to cut a notch or drill a hole in a joist. Whenever holes or notches exceed the limitations listed below, the lumber is weakened and a portion of the load supported by the cut member must be transferred properly to other joists.   Specifically for floor joists, holes should not be bored closer that 2 inches from a joist edge, nor should they be larger than 1/3 the depth of the joists. Notches are not allowed in the middle third of the span, where the bending forces are the greatest. Notches should be no deeper than 1/6 the depth of the joist, except at the ends where it can be no deeper than 1/4 the depth. Limit the length of a notch to 1/3 the joist depth.   At times, a notch may be cut so long that it becomes a rip. Unfortunately, ripping wide dimension lumber lowers the grade of the material and is unacceptable under all building codes. When a sloped surface is necessary, a non-structural member can be ripped to the desired slope and fastened to the structural member in a position above the top edge.

Figure 1: Permitted holes and notches

Notches