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Heavy snow accumulation causes concern about roof snow load

Published: Dec. 29, 2021 at 8:48 AM AKST
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FAIRBANKS, Alaska (KTVF) - With all this snow accumulating, you might be worried about the snow load on your home or workplace and wonder if you should have your roof shoveled.

According to the Cold Climate Housing Research Center (CCHRC) at the University of Alaska Fairbanks, if your roof is built for the recommended load of 50 pounds per square foot (psf), you should be okay. Homes built before 1991, were required to carry 40 psf and older homes even less.

Snow loads can vary, depending upon the type of roof you have, the roof slope, and melting and re-freezing of snow and ice, among other factors. The rain and freezing rain the Interior has recently experienced has caused the light fluffy powder snow to become heavy and dense.

Snow loads in the 30 to 35 pounds per square foot range could be a risk for some roofs and cause them to collapse. Mobile home roofs are usually flat and are built to carry just 20 pounds per square foot. RV’s, canvas quansots and greenhouses are not built to hold lots of snow and should be attended to as needed.

An underbuilt roof structure can also be at risk for collapse from imbalanced loading. For example, if snow slides off one side of the roof yet remains on the other, this puts stress on the roof structure due to the shift in weight distribution.

According to Meteorologist Jonathan Chriest with the National Weather Service in Fairbanks, snow load can vary widely across distance.

“We have a station out at Creamers Field that’s currently at 22 pounds per square foot of snow load. We have a station out at Chena Lakes that is currently reading 30 pounds per square foot of snow load, and we recently took a snow core here at the office, just today. So up at UAF (University of Alaska Fairbanks), we also recorded 20 pounds per square foot, up here at the office.”

“There are a lot of things that can happen that can change the snow drastically, such as drifting snow, ice damming, many other factors that factor into the snow load on an particular roof.” said Chriest.

Building codes in the City of Fairbanks calls for roofs to withstand a minimum of 50 pounds per square foot. However, homes built before 1991 may not be able to withstand that much and are at a higher risk of collapse. Also, there are no building codes outside of the city limits.

Building Official Clem Clooten for the City of Fairbanks discusses how residents can have their structure’s durability checked. “If they don’t know when it was built and if it was built outside the city limits, then they would have to have a structural engineer review the calculations or check with the trust manufacturers to see if you can find what the strength of the roof was when it was designed.” Clooten also warned about water pooling on roof snow and to make sure it is able to drain off properly.

For more information about snow load, please contact the Cold Climate Housing Research Center at 907-457-3454 and the University of Alaska Cooperative Extension Service at 907-474-6366.

One last cautionary thought, when contemplating if you should get the snow removed from your roof, the snow is usually here until May and the chance for a lot more snow to accumulate is a given. Having the snow removed now should give you peace of mind and will put less stress on your roof moving forward this winter.

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