Section 246-359-300 - Ceiling framing for wood framed construction and concrete masonry units (CMU)(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)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)Ceiling joists must be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.(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)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-A Western Wood Products Table for Hem-Fir #2 Ceiling 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 |
Wash. Admin. Code § 246-359-300
Amended by WSR 15-13-091, Filed 6/15/2015, effective see belowStatutory Authority: RCW 70.114A.081. 99-03-065, § 246-359-300, filed 1/18/99, effective 2/18/99.