502.8 Drilling and notching. Structural floor members shall not be cut, bored or
notched in excess of the limitations specified in this section. See Figure 502.8.
502.8.1 Sawn lumber. Notches in solid lumber joists, rafters and beams shall
not exceed one-sixth of the depth of the member, shall not be longer than onethird
of the depth of the member and shall not be located in the middle onethird
of the span. Notches at the ends of the member shall not exceed onefourth
the depth of the member. The tension side of members 4 inches (102
mm) or greater in nominal thickness shall not be notched except at the ends of
the members. The diameter of holes bored or cut into members shall not
exceed one-third the depth of the member. Holes shall not be closer than 2
inches (51 mm) to the top or bottom of the member, or to any other hole
located in the member. Where the member is also notched, the hole shall not
be closer than 2 inches (51 mm) to the notch.
Do not make this mistake. I have had many a friend call me only to have me give them the bad news.
Nothing like pulling all your wires out to have the carpenters sister all the joists.