Reaching the Roof: Specifying Fixed Access Aluminum Ladders for Safety and Efficiency
Installed in virtually every commercial structure, fixed access aluminum ladders are a necessary feature for maintaining both building equipment and occupant safety.
Use the following learning objectives to focus your study while reading this month’s Continuing Education article.
Learning Objectives - After reading this article, you will be able to:
- Summarize code standards for fixed access ladders that ensure the health, safety and welfare of users.
- Discuss the safety and code compliance aspects of different types of fixed access ladders.
- Identify uses and applications of fixed access ladders.
- Evaluate design features and materials required for safe fabrication and installation.
From biblical times, ladders have occupied an iconic role in art and allegory. They are a metaphor for moving upwards, whether to heaven or a cliff-face dwelling. Cave artists translated the metaphor literally when they painted unmistakable images of ladders, as did stone masons who carved angels gracing ladders on medieval cathedrals.
Today, we prefer to think of them as tools for reaching roofs and upper stories that can be broadly categorized as portable ladders or fixed access ladders. A portable ladder, as the name implies, refers to those ladders, which can be carried. A fixed access ladder is a ladder, which is permanently attached to a structure either at one or both ends.
Fixed access ladders are found in virtually every commercial building, most often required by building codes as a means of reaching equipment located on the roof. Yet, a fixed access ladder, being relatively small and often an afterthought to the design and construction of an entire building, is sometimes ignored and its design left to the last moment or hurriedly specified in response to urging from the building inspector. Unfortunately, uninformed specification, inadequate communication with fixed ladder manufacturers and lack of knowledge regarding code compliance can and has, led to faulty ladder installations with potentially dangerous results. A knowledge of ladder materials and construction, code compliance and safety issues, plus the ability to evaluate site requirements and interpret manufacturers specifications are therefore all critical.
LADDER MATERIALS AND CONSTRUCTION
Traditionally constructed from wood, ladders were heavy and time consuming to fabricate on site. The introduction of aluminum and mass produced steel in the 19th century not only transformed the way ladders could be constructed, but radically opened up manufacturing possibilities for fixed ladders. While an improvement over wood, steel has similar disadvantages. However aesthetically desirable for an urban loft ladder, it is, like wood-heavy, costly to ship, requires considerable manpower and equipment to install and is subject to rust and corrosion.
Aluminum, on the other hand, is lightweight, flexible, can be engineered to precise conditions off site, is not subject to rust and corrosion and is the ideal material for the construction of fixed access ladders and their numerous industrial and commercial applications. Structural aluminum is supplied in various grades, which affect the strength, sturdiness, thickness and width of ladder components. Ladder manufacturers most commonly select grades 6063-T5 and 6061-T6.
Aluminum alloy 6063 grades are mostly used in extruded shapes for architecture, particularly window frames, door frames, and roofs. Aluminum alloy 6061 is used in aircraft structures, yachts, and automotive parts, depending on the temper, or heat treatment, of the material. In functional terms, aluminum alloy 6061-T6 is 119 percent stronger than the more commonly used 6063-T5 extrusions and therefore offers enhanced safety and longer life. It is also 58 percent harder which provides more resistance to scratches and abrasions.
Ladder brackets. Critical features of a fixed access ladder are the ladder brackets,which anchor the ladder to the structure. As with the composition of ladder material, the aluminum grade of the brackets is crucial, as are the number of brackets and their size, for ensuring a safe, secure and ergonomic ladder system. The use of high strength aluminum alloy 6061-T6 provides stiffer brackets which means less deflection when the ladder is being used. Installing two 3/8-in. bolts rather than a single 3/16-in. bolt on each side to attach the bracket to the ladder further enhances security.
When specifying ladders, architects should note the grade of aluminum to be used in manufacturers' specs. This, and other details of materials, should be determined by the specific requirements of the installation and the need for long term durability.
Larger-sized ladder brackets add strength, stiffness and security to ladder installation
Ideally, the design and construction of fixed access aluminum ladders should reflect the ergonomics of climbing ladder steps.
Vertical ladders. For vertical ladders fixed at 90 degrees, round rungs provide a stronger, more comfortable grip when pulling up. Round rungs also provide a more natural support for the feet, which pivot while climbing straight up. Ideally, rungs should have a serrated surface for a no-slip grip and be secured to the side rails with cast aluminum connectors, using four solid aircraft rivets on each rung. This gives a permanent, no-twist installation that has a combined shear strength of over 3600 lbs. for each rung. For anchoring strength, fixed ladders should come with mounting brackets that are 3/8-in. thick aluminum bar, pre-punched to provide 16-in. on center mounting holes. Brackets should be provided for every six feet in length of the fixed ladder.
Angled ladders. For angled ladders, flat steps give the best support when climbing at an angle. Ships and folding ladders should be available with steps of varying depths. To best suit climbers' feet, ladders with a greater angle from the floor-60 degrees for example-should have a greater depth. Steps should also be permanently affixed to the side rails using eight solid rivets per step, with non-slip ridges on the top. Flush or extended handrails need to be designed to fit the users' hands, giving a comfortable grip when steadying the body during climbing.
|Glossary for Fixed Access Ladders|
cage -a guard that is fastened to the side rails of the fixed ladder or to the structure to encircle the climbing space of the ladder for the safety of the person who must climb the ladder.
cleat -an industry term for what is commonly known as a €˜rung' or €˜step.' A ladder crosspiece of rectangular cross section placed on edge upon which a person may step while ascending or descending a ladder.
double-cleat ladder -a ladder with a center rail
to allow simultaneous two-way traffic for employees
ascending or descending.
extended handrails - the side rails of through or side-step fixed ladders must extend 42 inches (1.1 m) above the top level or landing platform
flush mounting- the top end of the ladder is at the same level as the surface of the area it reaches
folding ladder - a ships ladder that is anchored and hinged at the upper end. It can be extended while in use and folded against the wall for storage.
ladder safety device - any device, other than a cage or well, designed to eliminate or reduce the possibility of accidental falls. They may be used in lieu of cage protection. No landing platform is required in these cases.
landing platform -provides a means of interrupting a free fall and serves as a resting place during long climbs.
point of access -all areas used by employees for work-related passage from one area or level to another.
riser height -the vertical distance from the top of a tread or platform/landing to the top of the next higher tread or platform/landing.
side exit - an exit to the side of the ladder, such as when the ladder is perpendicular to the landing platform.
side rails or handrail -a rail used to provide employees with a handhold for support.
side-step fixed ladder -a fixed ladder that requires a person to get off at the top to step to the side of the ladder side rails to reach the landing.
single-cleat ladder -a ladder consisting of a pair of side rails connected together by cleats, rungs or steps.
ships ladder - originally referred to a portable set of steps held in place temporarily along a ship's side for access. Also called an "inclined ladder."
through fixed ladder -a fixed ladder that requires a person getting off at the top to step between the side rails of the ladder to reach the landing.
tread depth -the horizontal distance from front to back of a tread, excluding nosing, if any.
well- also known as a shaft. A walled enclosure around a fixed ladder that provides the person climbing the ladder with the same protection as a cage. Wells are part of the permanent structure, whereas cages are part of the ladder.
STANDARDS AND SAFETY
The American National Standards Institute (ANSI) and the Occupational Safety and Health Administration(OSHA) issue national standards regarding fixed ladders. Both sets of standards are virtually the same as each organization takes turns to institute changes.
Titled ANSI A14.3-2008 American National Standard for Ladders - Fixed - Safety Requirements is available from webstore.ansi.org. ANSI standards detail specifications on the various materials, construction requirements, test requirements, usage guidelines and labeling/marking requirements for fixed access ladders (CHECK).
OSHA Regulations (Standards - 29 CFR) Fixed ladders. - 1910.27 are available for download at www.osha.gov. OSHA also publishes a Booklet Guide to the 1910.27 regulations titled Stairways and Ladders, A Guide to OSHA Rules, OSHA 3124-12R 2003 (www.osha.gov/Publications/OSHA3124/osha3124.html).
The latter is a general overview of the OSHA standards and covers the rules for all ladders included fixed ladders (see sidebar).
Ladders in general
€¢ Ladder rungs, cleats, and steps must be parallel, level, and uniformly spaced when the ladder is in position for use.
€¢ Ladders must not be tied or fastened together to create longer sections unless they are specifically designed for such use.
€¢ Two or more separate ladders used to reach an elevated work area must be offset with a platform or landing between the
ladders, except when portable ladders are used to gain access to fixed ladders.
€¢ Ladder components must be surfaced to prevent injury from punctures or lacerations, and prevent snagging of clothing.
€¢ Individual rung/step ladders must extend at least 42 in. (1.1 m) above an access level or landing platform either by the continuation of the rung spacing as horizontal grab bars or by providing vertical grab bars that must have the same lateral spacing as the vertical legs of the ladder rails.
€¢ Each step or rung of a fixed ladder must be able to support a load of at least 250 pounds (114 kg) applied in the middle of the step or rung.
€¢ The rungs of individual rung/step ladders must be shaped to prevent slipping off the end of the rungs.
€¢ The rungs and steps of fixed metal ladders manufactured after March 15, 1991, must be corrugated, knurled, dimpled, coated
with skid-resistant material, or treated to minimize slipping.
€¢ The side rails of through or side-step fixed ladders must extend 42 in. (1.1 m) above the top level or landing platform served by the ladder.
Cages for fixed ladders
€¢ Horizontal bands must be fastened to the side rails of rail ladders or directly to the structure, building, or equipment for
€¢ Vertical bars must be on the inside of the horizontal bands and must be fastened to them.
€¢ The inside of the cage must be clear of projections.
€¢ The bottom of the cage must be between 7 ft (2.1 m) and 8 ft (2.4 m) above the point of access to the bottom of the ladder.
€¢ The top of the cage must be a minimum of 42 in. (1.1 m) above the top of the platform or the point of access at the top of the ladder. Provisions must be made for access to the platform or other point of access.
Wells for fixed ladders (part of the permanent structure)
€¢ Must be free of projections.
€¢ The bottom of the well above the point of access to the bottom of the ladder must be between 7 ft and 8 ft.
The following code requirements are the most important for architects, specifiers and project managers to be familiar with (for fuller code wording see sidebar):
Requirement for fixed ladder
A double-cleated ladder or two or more ladders must be provided when ladders are the only way to enter or exit a work area having 25 or more employees, or when a ladder serves simultaneous two-way traffic.
*A fixed ladder must be able to support at least two loads of 250 pounds each, between any two support brackets.
Required when ladders are used to ascend to heights exceeding 30 feet. Or required for every 20 feet if no cage, well or ladder safety device is provided.
Cages or safety devices are required for fixed ladders with a length of more than 20 feet to a maximum unbroken length of 30 feet. A safety device is generally more expensive to install than a cage. The bottom of the cage must be between 7 ft and 8 ft above the point of access to the bottom of the ladder. The top of the cage must be a minimum of 42 in, above the top of the platform or the point of access at the top of the ladder.
DESIGNING FIXED ACCESS LADDERS
A first and obvious step to specifying a fixed access aluminum ladder is to know the particular function and location of the ladder since the location dictates the type of ladder required:
- How much space is there for accessing the ladder? What is the daily traffic pattern of the area at the base of the ladder? This will help determine the type of ladder required:, a ships ladder at 60 degrees takes up far more area than a folding ladder at 80 degrees or a vertical fixed ladder .
- How often is the ladder going to be used? A ships ladder at 60 degrees is easier to climb than a fixed vertical ladder and is therefore safer. If an employee rest area is located on a mezzanine floor-as is often the case in fabricating facilities, the ladder will have heavy use. A ladder accessing roof equipment would have regular but far less use.
- Are people who are using the ladder going to be carrying heavy or awkward loads? Is the ladder accessing a mezzanine where inventory is stored? Often concrete tilt-up buildings are one story tall and use fixed access ladders to reach storage spaces.
- Who will be using the ladder?
In a somewhat misguided concern for safety, one designer specified a fixed ladder should support loads of 1000 pounds. In this particular case the ladder was not reaching a storage area, and employees, firemen, inspectors and service contractors, were expected to use it on an irregular basis. Not only would the ladder have been excessively expensive as a result of custom fabricated components, but unnecessary given that probably no person weighing 1000 pounds would be climbing it. The loading specified by OSHA and ANSI has been developed from years of study based on usage. However, when exceptional conditions warrant, ladders can be designed for additional loading.
- What is the purpose of the ladder? Exterior roof access, roof hatch access or mezzanine access?
Exterior Roof Access
Fixed vertical wall ladders provide permanent exterior roof access. They are ideal for chimneys, towers, vats, antennas, tanks, water treatment plants, refineries and other industrial or marine applications. Remember that ladders in excess of 20 feet require cages and rest platforms are required for each 30 feet of height. Side exits and ladder step through are other means of access and egress. Typical specifications include side rails with 1-1/8-in. round rungs that are serrated and secured with cast aluminum connectors, 4 solid rivets and 3/8-in. thick brackets mounted to the walls.
Several different vertical ladder configurations include: Handrails over the roof, side exit, roof return and parapet return.
Right: Exterior roof access vertical fixed ladder with handrails extending 42 in. over the roof. Left: Configuration showing placement of the security door.
Exterior roof access ladder with side exit. A cage is required because the ladder is in excess of 20 feet. Note the bottom of the cage must be between 7 feet and 8 feet above the point of access to the bottom of the ladder. Also note the flaring dimensions of the enclosure at the lower end of the cage. This is a code requirement to aid the ladder user in climbing the ladder.
Exterior roof access fixed ladder with roof return. The roof return is the portion of the ladder mounted above the roof and means that the ladder is returning to the roof.
Exterior roof access showing parapet return and cage. The parapet return is the portion of the ladder that returns from the parapet to the roof level. The return would be required anytime the distance from the parapet to the roof is greater than about 12" (305mm)
Roof hatch access
Governed by OSHA Regulations 1910.23 & 1910.27, roof top hatches should provide safe egress and ingress through the roof. Hinged and guarded by railings with a standard height of 12 in., they are in effect a ladderway floor opening, the roof being the floor or platform.
Fixed access options for roof hatch access include ships ladders permanently angled at different degrees, folding ladders, vertical fixed wall ladders and retractable ladders.
Ships ladders are designed for access to roof hatches, mezzanines, equipment lofts and other restricted spaces. They usually include heavy duty aluminum top and bottom brackets for a fixed, permanent installation. Typically, they are available in 60 degrees 70 degrees and 80 degrees with maximum heights varying between 15 feet and 20 feet. They can be specified with or without side rails and with or without extended side rails.
Ships ladder fixed at 60 degrees with extended handrails for easy climbing, this model has a maximum height of 15 feet.
Folding ladders are suitable for limited space and can be folded away when not in use. Typically they are available with no-marking, solid rubber feet for secure floor contact when not in use and have optional flush handrails.
Folding ladder hinged at the top extends 80 degrees from the horizontal.
Retractable ladders.Designed for space saving interior access to roof hatches from small rooms. They are ideal for restaurants, tool storage rooms, workshops and mini warehouses.
Retractable ladder saves space when accessing roof hatches from the interior of small rooms.
|Upper bracket detail for retractable ladder. Rotating brackets allow the ladder to be extended.|
Ships ladders and folding ladders with required side rails are generally specified for mezzanine access.
A 70-degree folding ladder with hinged bracket for mezzanine access requires an extended handrail.
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 3 1/2 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 3 1/2 feet minimum.
ANSI A14.3 (22.214.171.124) "The side rails of through or side-step ladders shall extend The side rails of through or side-step ladder extensions shall extend 3 ft 6 in. 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-ft 6-in (42-in.) 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 (126.96.36.199): 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 in..."
Conclusion: The 7-in. 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-in. 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-in. If there are gutters located at the roof level that are more than 5-in. 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-in.
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 2-1/2-in.
ANSI A14.3 (188.8.131.52) "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 in. or more than 12 in. If the normal step-across distance exceeds 12 in., a landing platform shall be provided to reduce the distance to between 7 and 12 in."
Conclusion: Gutters or obstructions greater than 5-in. 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-ft. 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 in. All vertical spacing of the rungs from the center of the first rung throughout the length of climb shall be 12 in. 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" (305mm) 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).
CONCLUSIONFixed 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.