Reaching the Roof: Specifying Fixed Access Aluminum Ladders for Safety and Efficiency
Case Studies
While the majority of fixed access aluminum ladders are specified and installed correctly according to code, manufacturers tell many stories of things not going quite right. On one occasion the contractor on the job site removed and reconfigured the ladder brackets to make the ladder fit, thereby making the ladder unsafe. Fortunately, the manufacturer discovered the change before the building was occupied. Other examples reveal the challenges of designing according to code:
CASE STUDY 1: ROOF TO ROOF ACCESS LADDER
For aesthetic reasons, two architects wanted a roof-to-roof access ladder that would not protrude above the upper roof level. They decided on a retractable safety post typically used on hatch access ladders, thinking that this would meet the requirements for code. It does not:
OSHA 1910-27 (d) (3): "Ladder extensions." The side rails of through or side-step ladder extensions shall extend 31/2 feet above parapets and landings. For through ladder extensions, the rungs shall be omitted from the extension and shall have not less than 18 nor more than 24 inches clearance between rails. For side-step or offset fixed ladder sections, at landings, the side rails and rungs shall be carried to the next regular rung beyond or above the 31/2 feet minimum.
ANSI A14.3 (5.3.2.1) "The side rails of through or side-step ladders shall extend The side rails of through or side-step ladder extensions shall extend 3 feet 6 inches above the top of the access/egress level or landing platform served by the ladder."
Conclusion: Because this is a "through" ladder where a climber steps through and beyond the ladder onto the walking surface, the side rails must extend 3 feet 6 inches (42 inches) above the last step. This will give the user something to hold onto as he or she prepares to climb down the ladder.
CASE STUDY 2: CLEARANCES
This is an issue that confuses most specifiers. Both OSHA and ANSI codes state that the minimum clearance behind the ladder rungs is 7 inches.
OSHA 1910.27(c)(4) states: "Clearance in back of ladder." The distance from the centerline of rungs, cleats, or steps to the nearest permanent object in back of the ladder shall be not less than 7 inches, except that when unavoidable obstructions are encountered.
ANSI A14.3 (5.4.2.1): The perpendicular distance from the centerline of the steps and rungs or grab bards, or both, to the nearest permanent object in back of the ladder shall be not less than 7 inches.
Conclusion: The 7-inch minimum clearance must be maintained throughout the length of the entire ladder, not just at the rungs. Brackets can be made larger in order to clear small conduit pipes or eave overhangs.
CASE STUDY 3: STEP ACROSS DISTANCE
This case study relates to Case Study 2, but deals with gutters at the roof level. Codes require a minimum clearance of 7 inches from the centerline of the rung to the closest obstruction. Further, codes state that a climber may not "step across" a distance greater than 12 inches. If there are gutters located at the roof level that are more than 5 inches from the edge of the roof, a landing platform is required because the distance from the ladder-which is anchored beyond the outside edge of the gutter-to the roof is more than 12 inches.
OSHA 1910.27(c)(6): "Step-across distance." The step-across distance from the nearest edge of ladder to the nearest edge of equipment or structure shall be not more than 12 inches, or less than 21/2 inches.
ANSI A14.3 (5.4.2.2) "For a through ladder, the step across distance from the centerline of the steps or rungs to the nearest edge of the structure, building, or equipment shall not be less than 7 inches or more than 12 inches. If the normal step-across distance exceeds 12 inches, a landing platform shall be provided to reduce the distance to between 7 and 12 inches."
Conclusion: Gutters or obstructions greater than 5 inches will require a landing platform (either connected to the building or as a part of the ladder) in order to meet these clauses of the code requirements.
CASE STUDY 4: STEP AND RUNG SPACING
Many architects and specifiers are confused by this part of the standards. Codes read that the spacing should be consistent throughout the length of climb, but the initial step or rung can be adjusted. Most ladder heights are not exactly in 1-foot increments so the bottom step or rung is where that adjustment is made.
OSHA 1910.27 (b)(1)(ii). The distance between rungs, cleats, and steps shall not exceed 12 inches and shall be uniform throughout the length of the ladder.
OSHA 1910.27(d)(2)(iii) One rung of any section of ladder shall be located at the level of the landing laterally served by the ladder. Where access to the landing is through the ladder, the same rung spacing as used on the ladder shall be used from the landing platform to the first rung below the landing.
ANSI A14.3 (5.1.1) "The vertical spacing of the first rung of climb shall be permitted to be adjusted within the range of 14 inches. All vertical spacing of the rungs from the center of the first rung throughout the length of climb shall be 12 inches and uniform in the same length of climb."
ANSI A14.3 (5.3.1) "Top Step or Rung. The top of a step or rung of a ladder shall be level with the top of the access/egress level or landing platform served by the ladder."
Conclusion: Although codes state that the rungs or steps shall be uniform in spacing, and 12 inches (305 millimeters) on centers, they do allow for adjustment at the first rung of climb. Ladder rungs are spaced over the length of climb starting at the top as indicated in OSHA 1910.27 (d)(2)(iii) and ANSI A14.3 (5.3.1).
Conclusion
Fixed access ladders are necessary tools for the efficient functioning of virtually all commercial buildings and the health, safety and welfare of their occupants. As with all tools, they need to be evaluated in terms of the code standards that govern their use and the how and where they are employed. In centuries past, an image sufficed for understanding the role and purpose of ladders. Today, all ladders, especially fixed access ladders, demand much, much more.
|
ALACO is a manufacturer of special purpose and custom designed ladders to fit a variety of residential, commercial and industrial applications. Established in 1946, ALACO now manufactures over 800 different models of aluminum, wood and fiberglass ladders, including a complete line of commercial and designer rolling ladders. www.alacoladder.com |
Notice
