Are you concerned about snow load on your building? Well, you have good reason for caution as data shows that it can be quite costly if not proactively managed in the right manner.
In February of 2015, New England accumulated over 100 inches of snow after more than a month of blizzard like conditions. “More than 160 roofs have collapsed or faced imminent collapse since Feb. 9 in Massachusetts alone, the epicenter of this season’s roof collapse epidemic,” Sam Schultz reports for Channel 4 NBC New York News. The article goes on to report New Hampshire had 10 roofs collapse over the course of that year as well (Schultz). Snow load on commercial roofs can prove to be very costly and dangerous for property managers everywhere.
There are a couple things to consider when thinking about snow load on the roof of your commercial building: Uniform and Nonuniform Snow Load.
Uniform Snow Load is when the snow places a vertical, downward force equally on the roof of your building. Nonuniform Snow Load is when you have lateral force and unequal weight distribution placed on your building with things like snow drift. (O’Rourke 64)
Where property managers can run into problems is when they experience a lot of high winds (Nonuniform Snow Load) and snow that melts, refreezes and takes on subsequent snow on two level roofs. “Insurance records suggest that roughly 75 percent of snow-related structural damage comes from drift loads on two-level roofs.” (O’Rourke 65). Snow drifts can get really dangerous as we have seen snow drifts 20 feet wide by 300 feet long on different commercial buildings so this is definitely something every property manager should pay close attention to. Usually, our team of commercial roofing experts will find little snow up on the higher roof, but it can blow from the higher to the lower level and hammer that lower roof.
Throughout the country, you have varying snow load requirements that are measured in pounds per square foot – ranging from approximately 40 to 65 pounds per square foot.
Our Supreme Team measures this by cutting out a 12” x 12” square, going straight down to the roof deck and putting that in a trash bag. Next, we measure the weight of the bag of snow on a scale to determine if we are breaching the international building code requirements for snow load. Sometimes, Supreme will bring in a structural engineer to give us expert advice on how much the snow is weighing, further ensuring we are doing what is safest and in the best interests of the property manager.
Some key interior visual signs to watch for in determining if you are having problems with snow load on your commercial building include:
- Deflection or separation of the roof deck
- New cracks in the roof
- Bowing or flexing of the roof deck
- Water leaks or holes in the roof
As soon as any of the above signs of snow load damage are observed, you should contact one of our commercial roofing experts immediately to ensure no further damage is done.
O’Rourke, Michael J. “Snow Load on Buildings: Statistics of Snowfall plus Small-Scale Simulations Help Engineers Design Buildings That Can Withstand the Loads of Rooftop Drifts.” American Scientist, vol. 85, no. 1, 1997, pp. 64–70. JSTOR, www.jstor.org/stable/27856692. Accessed 25 Jan. 2021.
Schultz, Sam. “New England’s Snowy Roof Collapse Epidemic: What You Should Know.” Channel 4 NBC News New York. 25 February 2015.