Rooftop avalanches cause hundreds of millions of dollars in property damage, personal injury and even death each year—clearly life-health-safety related. Proper, job-specific design of a qualified snow retention system dramatically reduces building owner/designer liability when sliding snow presents a hazard.
Liability
Numerous snow guard vendors have appeared in the market, each claiming to be the best, ultimate, first or strongest. How does a designer discern prudent product selection from sales rhetoric? While engineered snow retention systems complement the roof, this market space is completely unregulated! There are no codes or standards that govern—no “snow guard police.” Many applications are not specifically engineered for design loads. The only policing within this field is by the architect, specifier— and often contractor.
“Furnish snow guards, typical” plan callouts; and “… as recommended by manufacturer” spec language is rolling the dice, making the contractor the ultimate decision-maker for adequacy and product selection. Without vetting, even when installed to the manufacturer’s instructions, it may fail, leaving the designer and contractor together liable. Protection from this liability starts long before the project is bid.
Science
The service loads applied to a snow guard system are a relatively simple calculation varying with site specifics known to the design team: 1) the design roof snow load, 2) roof slope and, 3) roof (or rafter) length. These three factors determine the force that a system must resist for any roof surface, according to the Metal Construction Association (MCA), and should be included in plans and specs requiring an engineered system.
Testing
To resist the forces applied to any system, the failure point must be known. Then, the population and frequency of the system and anchorage is determined so it cannot fail. Because multiple components comprise the system, a “load chain” results. The calculated force is transmitted through this chain into the building structure. Each link (component) in the chain must be proven by testing (or by engineering analysis). The weakest link determines the strength of the chain. Safety factors are applied to determine allowable structural capacity. Engineering cannot be completed without extensive testing.
Vet and Specify
Manufacturer transparency is requisite to vet a snow guard system. A vendor who lauds the capabilities of his system but fails to provide proof of those claims is just blowing smoke. MCA recommends the designer should scrutinize manufacturer certifications to ensure a safe, engineered application and long-term service. This transparency should extend from raw material sourcing through manufacture and product hand-off. Scrutiny of vendor evidence provides credibility and assurance to the owner. A qualified manufacturer will gladly provide proof of claims.
Proof of Testing
Anchorage to the roof should be tested and requires repetition. The connection strength of seam clamp-to-standing seam varies widely dependent upon clamp design, type/gauge of roof material, seam geometry, dimensioning and source. According to MCA, testing should be conducted by a third-party ISO 17025-accredited lab—specific to the profile and roof brand—with test reports furnished during design and later with submittals, proving anchorage values used in calculation. Ideally, panel-specific results should be published on the vendor’s website.
Proof of Engineering
Project-specific engineering must be provided by the vendor, according to MCA, and should incorporate the tested strength of the system with an appropriate factor of safety applied. Insist calculations are provided—preferably during product selection. Ideally, the vendor should offer a web-based calculator with real-time output showing calculations and allowable loads specific to your project, including product names of snow guard systems and specific brands of roof manufacturers. At a minimum, require these calcs with submittals. Better yet, have the vendor provide them stamped by a registered Professional Engineer.
Proof of Certified Manufacturing
How can you know the product tested is truly the product purchased? Systems may look the same, but alloys, tensile, yield and other mechanical properties are verified through certified manufacturing with third-party audits in an ISO 9001-15 compliant facility, not by physical appearance, according to MCA. Ask to see the current ISO Certificate. Ideally, it should be displayed on the vendor’s website.
Warranties
Does the manufacturer offer a meaningful performance (not just material) warranty? Obtain a copy prior to specification—and read the fine print! Ideally, it should be displayed on the vendor’s website. Will they be in business for the long-term to honor it if needed? Has the vendor substantiated its track record? How long the company has been in business is irrelevant. The question is, “How long and on how many projects has the system been in use?”
Further
Enforce the specification! A lack of code mandates provides a free pass to unqualified systems and serious potential liability. Require the vendor to provide a written statement of compliance with the Metal Construction Association documents “Metal Roof Design for Cold Climate” and “Qualifying Snow Retention Systems.”
Rob Haddock is the CEO and founder of S-5! Metal Roof Innovations Ltd., Colorado Springs, Colo. For more information, visit www.s-5.com.