Document Z59pNyXm22d50728D4XEGBed

Industrial Buildings and Plant Layout Stairs and walkways Stairs are taking the place of ladders in boiler rooms and other places both inside and outside of buildings Circular stairways should be avoided, but ifabsolutely necessary, should be designed with a minimum variation m tread width Treads should be covered v'lth a durable antishp material The preferred slope for a stairway is be tween 30 and 35 degrees from the horizontal (Fig 16-5 and Table 16-B) The most smt- TABLE 16-B SLOPE AND DIMENSIONS OF TREADS AND RISERS Angle of Stairway with Horizontal Riser (inches) Tread and Nosing (inches) 28 27' 29 25' 30 25' 31 26' 32 28' 33 32' 34 37' 35 44' 36 52' 38 2' 39 12' 40 25' 41 38' 42 53' 44 9' 45 26' 46 44' 48 4' 49 24' 50 O' 61/2 6% 6% 6% 7 7% 7% 7% 7 Vi 7% 7% 7% 8 8 Vs 8% 8% 8V2 8% 8% 8,3fi 12 11% 11 Vi 11% 11 10% 10>/2 10% 10 9% 9'/2 9% 9 8% 8'/2 8% 8 7% IVi 7% able slope for a fixed ladder is from 75 to 90 degrees A tread width of not less than 9Vi in plus a nonslip nosing of 1 in are recommended Riser height should not be more than 8 or less than 5 in , and should be constant for each flight A flight of stairs having four or more risers should have a standard handrail as specified in ASI Standard A12, Safety Code for Floor and Wall Openings, Ratlings, and Toe Boards Rails should be 30 to 34 in from the top sur face of the stair tread, measured in line with the face of the riser A center handrail is rec ommended for stairways over 88 in wide Consult applicable local and state codes Hardwood handrails should be at least 2 in diameter If standard black iron pipe is used, the diameter should be at least 1V& in Clearance between the handrail and the wall should be at least 1V4 m Rails are mounted directly on a wall or partition by means of brackets attached to the lower part of the handrail, to provide a smooth surface along the top and both sides of the handrail Brackets should be spaced not more than 8 ft apart, and the mounting should be able to withstand a 200 pound load applied on the handrail Because of space limitations, a permanent stairway sometimes has to be installed at an angle above 50 degrees Such an installation (commonly called an inclined ladder or "ship's ladder") should have handrails on both sides and open risers Design should not include long flights Landings every tenth or twelfth tread are recommended by some authorities At least one state limits the vertical distance between landings in factories to 12*/ ft Adequate illumination by lights located so thev do not cause glare is important Outside stairways should be covered to keep off rain, snow and ice, if possible It is good practice to enclose all inside stairs with partitions of fireproof or fireresistive material and to install approved fire doors to prevent the spread of smoke or flames from one floor to another Check codes and insurance men about this Stairs and landings should be able to sus tain a live load of not less than 100 pounds per square foot with a factor of safetv of four The original plans should specify elevated walkways and platforms on tanks, bins, big machinery, and other places where men must go during normal operations or for mainte nance purposes Conveyors should be pro vided with crossovers having nonslip sur faces Railings and toeboards should also be provided Many injuries are due to standing on lm- 412