In addition to WAC 296-24-74005, you must also ensure standard stairs:
(1) Are installed at angles between 30 to 50 degrees from the horizontal.
(2) Have a maximum riser height of 9.5 inches (24 cm).
(3) Have a minimum tread depth of 9.5 inches (24 cm).
(4) Have a minimum width of 22 inches (56 cm) between vertical barriers (see Figure D-8 of this section).
EXCEPTION: | Subsections (2) and (3) of this section do not apply to standard stairs installed prior to October 1, 2020, provided those stairs meet the dimension requirements specified in Table D-1 of this section or they use a combination that achieves the angle requirements of subsection (1) of this section. |
TABLE D-1
Angle to Horizontal | Rise (in inches) | Tread Run (in inches) | |||
30°35' . . . . | 6 1/2 | 11 | |||
32°08' . . . . | 6 3/4 | 10 3/4 | |||
33°41' . . . . | 7 | 10 1/2 | |||
35°16' . . . . | 7 1/4 | 10 1/4 | |||
36°52' . . . . | 7 1/2 | 10 | |||
38°29' . . . . | 7 3/4 | 9 3/4 | |||
40°08' . . . . | 8 | 9 1/2 | |||
41°44' . . . . | 8 1/4 | 9 1/4 | |||
43°22' . . . . | 8 1/2 | 9 | |||
45°00' . . . . | 8 3/4 | 8 3/4 | |||
46°38' . . . . | 9 | 8 1/2 | |||
48°16' . . . . | 9 1/4 | 8 1/4 | |||
49°54' . . . . | 9 1/2 | 8 | |||
 |
Figure D-8