When heavy snow meets fierce winds, even the best-engineered buildings can collapse. That’s why it’s important to be adequately prepared and insured for this type of peril.
How snow load can damage your buildings:
Snow load is the downward force on a building’s roof by the weight of accumulated snow and ice. The roof or the entire structure can fail if the snow load exceeds the weight the building was designed to shoulder, or if the building was poorly designed or constructed. It doesn’t take a blizzard to cause problems; an imbalance of drifting snow can cause one part of a roof to give, causing a domino effect that affects the rest of the structure.
“Wood structures typically will give a warning of imminent failure with audible creaking or visible bowing of rafters,” says Randy Tinker, P.E., Risk Management Property Engineer, Property Engineering Group, Nationwide Agribusiness Insurance Company, Des Moines, Iowa. “Metal structures, unfortunately, often don’t exhibit signs of stress before failure.”How much snow is too much?:
Calculating the snow load on your building takes more than an educated guess. The University of Wisconsin Cooperative Extension Service says that a ballpark estimate of snow load can be made with the following formula:
Calculated Roof Loading (lb/ft2) = Depth (ft) x Density (lb/ft2 /ft depth). The approximate density (lb/ft2 /ft depth) for light snow is 5-20, packed snow 20-40, packed snow with ice 40-58, and ice 58.
For example, a roof with 3 feet of light snow has an estimated roof load of 60 pounds per square foot (3 ft depth X 20 lb/ft2/ft depth density = 60 lb/ft2). You should know the roof weight limits for your buildings.
What you can do:
Some failures can be prevented with careful snow removal. The University of Wisconsin Cooperative Extension Service offers the following suggestion:
Hire a licensed/insured commercial roofing company that is experienced in roof snow removal as they will avoid causing damage to the roof by chipping or picking away at the ice.
Note that not all snow needs to be removed. A thin layer of snow can protect the roof from damage while snow is being removed.
Insurance checklist:
A few minutes can give you reassurance during a heavy-snow winter. Check with your insurance agent to:
- Confirm that your property insurance covers roof or building failure due to snow load.
- Make sure the policy pays for actual replacement costs, so you’re not out in the cold if you have to rebuild.
Once the snow starts to fly, do not hesitate to call NIR to evaluate and execute your snow removal needs on your commercial roof.
