We have all seen this style of ladder and many have questioned their use. Are they a “compliance alternative” to fixed stairs for those spaces where there is not enough room for the traditional stairs (as shown in the photo above). The bottom line… OSHA accepts this type of ladder, but under the following circumstances…
1. It must be designed, installed, used and maintained in accordance with the manufacturer’s recommendations AND in accordance with the following requirements:
a. The stair will be installed at a 70-degree angle or less.
b. The stair shall be capable of withstanding a minimum uniform load of 100 pounds per square foot with a design factor of 1.7 and the treads shall be capable of carrying a minimum concentrated load of 300 pounds at the center of any treadspan or exterior arc with a design factor of 1.7. If intended for greater loading, construction shall allow for that loading.
c. The stair shall be equipped with a handrail on each side to assist the user in climbing or descending the stair.
Click Here for OSHA’s STD Directive on Alternating Tread Type Stair.
This is what an engineering firm stated about their limited use of these ladders in industrial settings…
They are legal for industrial use in the USA, under international codes for mezzanines, in Canada as “secondary stairs for convenience purposes” and in the UK for access to lofts and bedrooms that do not have the only bathroom. Another source says “codes do not require stairs to unoccupied attics and lofts, so it’s up to the local code inspector a ladder or stair that does not meet rise and run requirements.”
MI-OSHA has the most specific requirements, which come from national building codes.
R 408.10228. Alternating tread-type fixed industrial stair.
Rule 228.
(1) An alternating tread-type fixed industrial stair shall have a series of treads or steps attached to a center support rail in an alternating manner so that a user of the stairs does not have both feet at the same level at the same time. The center support rail shall be installed at an angle of between 50 and 70 degrees from the horizontal.
(2) Stair rails shall be provided on both sides of alternating tread-type stairs and be of such a configuration to provide an adequate handhold for an employee who grasps the rail or rails to avoid falling.
(3) A minimum distance of 6 inches shall be provided between the stair rail and any other object.
(4) A minimum of 12 inches shall be provided between the stair rails of an adjacent alternating tread-type stair.
(5) An alternating tread-type stair shall comply with all of the following provisions:
(a) Be designed and constructed to carry a load which is not less than 5 times the normal live load, but not less than 1,000 pounds.
(b) Have a minimum overall width of 22 inches.
(c) Have a minimum width of 17 inches, not to exceed 24 inches between the handrails.
(d) Each tread of an alternating tread-type stair shall have all of the following:
(i) A minimum overall length of 8 inches.
(ii) A minimum width of 7 inches at the nose.
(iii) A maximum rise of 12 inches to the next tread surface of the alternating tread.
(iv) A minimum of 5 inches of projected tread surface between consecutive treads. This projected distance shall be measured horizontally between the noses on consecutive stairs.
(v) A slip-resistant surface.
(e) Have a vertical clearance of not less than 7 feet from any tread nose to an overhead object. Projections such as pipes, raceways, air ducts, or fixtures between 5 and 7 feet above a tread nose are permissible if guarded and marked.
(6) Where a stair platform or landing is used, its width shall not be less than the width of the stair or less than 30 inches in length measured in the direction of travel. The initial tread of the stair shall begin at the same elevation as the platform or landing.
(7) A flight of alternating tread-type stairs shall consist of not more than a 20-foot continuous rise. An intermediate platform, as prescribed in subrule (6) of this rule, shall be used to provide relief where more than a 20-foot rise is necessary to reach the next level.
(8) An example of an alternating tread-type stair is shown as follows:
OSHA even intended to specifcially regualte their use in 2003 when they issued a “Proposed Rule” to walking and working surfaces.