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Snow Loading and Roof Safety - What Should You Do?

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Arctic Blast 2008As the snow continued to accumulate last week, then turned to rain and finally began to melt, we heard about roof collapses from St. Helens to Portland to McMinnville.

Yesterday, I asked Jim Nicks, BDS' Residential Inspections Manager, what advice he has about roof safety during future snowstorms and he offered the following tips:

  • Develop a snow removal plan for your structure by reviewing the original design documents and/or consulting with a design professional to determine the capacity of the roof and safe snow removal techniques. Many older buildings were not required to design for drifting snow loads.
  • Snow will drift at roof wall intersections such as changes in building height or parapet walls; pay attention to drifting snow areas first.
  • Do not use equipment on the roof, such as snow blowers, to remove snow and ice unless you are sure of the capacity of the roof to support such equipment.
  • When snow removal is necessary, remember that unsafe removal procedures may result in a collapse or injury to individuals on the roof or nearby. Consult a professional.
  • Rain after the snow will cause the weight to increase dramatically; be extra observant as the temperature warms and snow switches to rain or freezing rain.
  • Make sure roof drains are clear and draining properly. They may be covered in ice and allow water to pond under the snow and ice. Water is much heavier than dry snow; even a few inches of ponding water can cause a roof to fail.
  • Be watchful for new cracks in rigid ceiling materials, or new deflections or sagging in suspended ceiling systems.
  • In exposed roof systems look for signs of stress such as cracking, splitting, sagging or twisting in trusses, purlins, joists, beams and girders. If in doubt evacuate the building and consult a professional immediately.
  • Roof failures often occur at the exterior wall connections in buildings with flat roofs. Check the connections at the ledgers for signs of cracking, twisting or deflection.
  • Be aware of any unusual sounds such as cracking or creaking from the roof. Evacuate the building immediately if you have any suspicion the roof is over stressed.

Arctic Blast 2008Most importantly, remember - safety first! My brother-in-law fell and took out the Christmas lights while trying to shovel snow and ice off his roof last week. My sister tried to rescue him, tweaking her back, and my little nieces stood on the ground crying, "Daddy, Daddy!"

When in doubt, call a professional. December 21st was just the first day of winter and who knows what the next few months have in store for us.

Alisa Cour
Customer Service Manager


1 Comment


Dave Thompson

May 12, 2015 at 3:04 PM

Didn't know that rain after a snow storm would make the roof heavier. I thought the warm rain would melt some of the snow. Well that is good info to have because it snows here a lot, and I don't want anything bad to happen to my roof. So thank you for posting this awesome article on how to better take care of your roof when it snows.

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