1. (1) Notching at the ends of ceiling joists must not exceed one fourth the depth. Notches in the top or bottom must not exceed one sixth the depth and must not be located in the middle one third of the span.
2. (2) Holes bored in ceiling joists must not be within two inches of the top or bottom and their diameter must not exceed one third the depth of the rafter.
3. (3) Ceiling joists must be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.
4. (4) Allowable ceiling joist spans for Hem-Fir #2 or better must be in accordance with the spans and load conditions listed in Table 300-A.

5. (5) The department of health will allow spans using other wood species or grade or other load conditions when accompanied by structural calculations prepared by a structural engineer or architect.

   Table 300-AWestern Wood Products Table for Hem-Fir #2Ceiling Joists 10# Dead Load
   Ceiling Joist Size	Spacing—inches on center	Span—feet-inches
   2 x 6	12	14-5
   2 x 6	16	12-8
   2 x 6	24	10-4
   2 x 8	12	18-6
   2 x 8	16	16-0
   2 x 8	24	13-1
   2 x 10	12	22-7
   2 x 10	16	19-7
   2 x 10	24	16-0
   2 x 12	12	26-3
   2 x 12	16	22-8
   2 x 12	24	18-6

[Statutory Authority: Chapter 70.114A RCW and RCW 43.70.334 through 43.70.340. WSR 15-13-091, § 246-359-300, filed 6/15/15, effective 1/1/16. Statutory Authority: RCW 70.114A.081. WSR 99-03-065, § 246-359-300, filed 1/18/99, effective 2/18/99.]