1. (1) Notches on the ends of joists must not exceed one-fourth the joist depth, unless substantiated by engineering design or approved tests.
2. (2) Holes bored in joists must not be within two inches of the top or bottom of the joist, and the diameter of any such hole must not exceed one-third of the depth of the joist.
3. (3) Notches in the top or bottom of the joists must not exceed one-sixth the depth and must not be located in the middle third of the span.
4. (4) Joists in transverse floor framing systems, which do not have perimeter blocking, must not be drilled or notched, unless substantiated by engineering design or approved tests.

[Statutory Authority: RCW 43.22.340, [43.22.]355, [43.22.]360, [43.22.]432, [43.22.]440 and [43.22.]480. WSR 96-21-146, § 296-150C-1050, filed 10/23/96, effective 11/25/96.]