Engineering a Complete Anchor System: Part 2

Common Misconceptions

There are two common misconceptions related to the design of suspended access and fall protection systems:

There is one standardized system

Actually, each building is different in many ways and requires an individual approach and review (from the layout, quantity, and type of equipment). Many believe fall protection only uses permanent roof anchors and that rooftop davits are the standardized equipment for window washing systems.

Now, it is true that most fall protection systems are composed entirely of roof anchors and wall anchors, but those can’t act as a fall protection solution for all buildings. Some buildings will have architectural elements that make it impossible to implement standard equipment. Standard roof anchors are substituted for monorail fall protection systems, horizontal trolley rail systems, or guardrails.

Many factors must be considered before determining what equipment needs to be placed in window washing systems. Davit systems are great for specific systems.

A design needs to meet the code

While a design must meet all codes, guidelines, regulations, and standards, it is also important that systems work. It is common to see a design that meets code requirements but does not allow workers to perform their duties effectively and efficiently. A design must consider how workers will use equipment to alleviate function issues.

Rooftop davits are always used for window washing systems

Window washing davits are a staple of the industry, so it’s no wonder people are under the impression that they’re the standard system. However, that’s not the case. Davits are great for high-rise square buildings, but with more complicated architecture, there needs to be a sophisticated solution.

If a building had protruding balconies or varying elevations, a davit system would not be able to reach the facade, and an outrigger beam would need to be installed. Alternatively, if a building had an overhang that prevented window washers from a straight drop down, a monorail hoist system would need to be installed under the overhang so the window washers could hook themselves off.

When a drop distance is greater than 150m (492 feet), a davit cannot legally be installed in North America; the building would have to install a BMU (Building Maintenance Unit), which is a fully mechanized roof car that can be lowered to the building’s windows.

For buildings with a drop distance under 300 feet, window washing davits aren’t mandatory, and they’re not usually the preferred suspension method. Rather, the preferred system is permanent roof anchors laid out near the roof edge so that both the suspension lines and lifelines can be attached.

Using permanent roof anchors for suspension is dangerous

In mid-rise buildings, many window washers are suspended on chairs attached to rooftop anchor points. Often, this setup is regarded as unsafe—after all, the only thing keeping the worker suspended is a chair, some rope, and a few anchors—but this isn’t the case. Using a basic rooftop anchorage system and Bosun’s chair for suspension is significantly safer than a powered platform. Generally speaking, the simpler the system, the safer it is.

Codes and Regulations

The local jurisdictional authorities are concerned with fall protection issues and pay close attention to current codes.

• ANSI I-14.1 is a leading standard in the United States.
• OSHA has several code requirements (including New York Code Rule 21 and CAL-OSHA)
• The CSA in Canada has very strict requirements for such equipment (along with specific provincial requirements, such as the Ontario Ministry of Labour and British Columbia WCB rules).

Those are just a small sample size of the federal, provincial/state, regional, and international requirements. Interpreting each is certainly a daunting task!

Pro-Bel's Free Design Service

For the above reasons, Pro-Bel offers architects, building owners, construction managers, engineers, and general contractors a free design service for fall protection, suspended maintenance, and window washing equipment/systems. This service includes a proposed layout, customized specifications, and equipment details that will consider the codes, cost, effectiveness, and efficiency.

Read Part 1

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