Metal Construction News, July 2019

Snow Guard Science By Rob Haddock Would you be safe standing under that roof KNOW YOUR PRODUCTS The manufacture of snow retention systems is a completely unregulated industry There are no snow guard police to ensure that only engineered products are released to the market Rooftop avalanches are a life safety issue Every year cars are crushed and people are injured or killed from snow slides Often by default the contractor becomes the ultimate decision maker and may be assuming liability when it comes to the selection of under designed untested systems I n 2016 the tragic death of a 2 year old girl occurred after seven feet of snow tumbled off a cabin roof in Idaho A deadly rooftop avalanche took a mother and her son in 2018 near Lake Tahoe Nev In 2019 a woman in Wyoming and a man in Colorado were both killed in roof avalanche disasters H ow does it happen Avalanches have a scientific cause When the temperature sensitive bond between roof and snowbank breaks free an avalanche occurs As the roof warms from UV rays or building heat loss it melts the interface bond This melt water lubricates the slide Snow guards can prevent the slide by restraining the bank of snow but only if properly designed and engineered The forces of sliding snow vary with job specifics but can be scientifically calculated for any given project They are the forces that must be restrained by the snow guard system and should be proven adequate by its tested holding strength Liability of Installing Non Engineered Systems The market is inundated with snow stop systems for metal roofs each claiming to be the first best or some other superlative If the contractor believes all of the sales hype without vetting the pitfall is this even if the product is installed according to the manufacturers instructions but the system is under designed it will fail leaving the contractor holding a bagful of liability Protecting yourself from this liability starts long before the product gets on the roof H ow can a contractor vet the products they install Manufacturer transparency is at the heart of vetting a snow retention system A vendor who lauds the capabilities of his system but fails to provide proof of those claims is blowing smoke When selecting a snow guard solution a contractor should scrutinize manufacturer qualifications and demand transparency to ensure a safe engineered application and long term service on every project If the manufacturer has truly done his due diligence he will be pleased that you ask him to prove it Tensile load testing To resist the forces applied to any system we need to know at what point the attachment fails Then we can calculate the required population and spacing of the attachment so that it doesnt fail This requires an enormous amount of testing and the panel specific results should be published on the vendors website for your inspection If not it probably does not exist Long term performance Can the vendor substantiate his track record over years of time and prove service durability with interactive load testing tables Ask for this evidence Warranties Does the manufacturer offer a meaningful performance not just material warranty Are you confident that they will be in business several years down the road to honor it Ask for it prior to purchase and read the fine print Engineering calculations These must be provided by the vendor on a project specific basis and should incorporate the tested strength of the device with an appropriate factor of safety applied Insist these calculations be provided If you dont feel qualified to review the calculations have the vendor provide them stamped by a Registered Professional Engineer Experience The vendor should show evidence of experience and the systems track record You cannot make a product perform better than its design Has the vendor demonstrated sufficient expertise to do that F urther vetting should include Use of chemically and mechanically certified m aterial ask to see those certifications Testing by a third party A2LA accredited l ab ask to see the lab report specific to your r oof profile and manufacturer Following ASTM material standards require a l etter of compliance Utilizing certified manufacturing processes a nd third party audits in an ISO 9001 15 c ompliant facility ask for a current copy of t he ISO Certificate Download the Metal Construction Association MCA technical bulletin Qualifying Snow R etention Systems for Metal Roofing This i ndustry consensus document provides in valuable criteria for snow guard selection At a m inimum ask your vendor to provide a w ritten statement that their system fully c omplies with this document Protect Yourself and Your Customer Remember In the end the vendor claims become your promises Would you feel safe walking under that roof when its loaded with snow Rob Haddock is founder and CEO of S 5 Colorado Springs Colo For more information visit www S 5 com 34 METAL CONSTRUCTION NEWS July 2019