PDFWAC 296-874-20026
Make sure stair towers meet these requirements.
(1) You must make sure stair towers (scaffold stairways or towers) meet all of the following:
(a) Are positioned so the bottom step is not more than twenty-four inches (61 cm) above the scaffold supporting level;
(b) Are at least eighteen inches (45.7 cm) wide between stair rails;
(c) Have slip-resistant surfaces on treads and landings;
(d) Are installed at an angle of forty to sixty degrees from the horizontal.
(2) You must provide a landing platform at least eighteen inches (45.7 cm) wide by eighteen inches (45.7 cm) long at each level.
(3) You must provide guardrails on the open sides and ends of each landing.
Reference: | For requirements about guardrails, go to WAC 296-874-20064. |
(4) You must make sure steps meet all of the following requirements:
(a) Line up vertically between rest platforms;
(b) Have uniform tread depth, within one-quarter inch (0.6 cm), for each flight of stairs;
(c) Have uniform riser height, within one-quarter inch (0.6 cm), for each flight of stairs.
Note: | Riser height may have larger variations at the top step and bottom step of the entire stair system, but not at the top and bottom steps within each flight of stairs. |