PDFWAC 296-24-74025
Ship stairs.
In addition to WAC 296-24-74005, you must also ensure ship stairs (see Figure D-9 of this section):
(1) Are installed at a slope of 50 to 70 degrees from the horizontal;
(2) Have open risers with a vertical rise between tread surfaces of 6.5 to 12 inches (17 to 30 cm);
(3) Have minimum tread depth of 4 inches (10 cm); and
(4) Have a minimum tread width of 18 inches (46 cm).
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Figure D-9 - Ship Stairs