Design & DIY

Do I need to worry about snow load on my cabin roof?

a snow load on a snowy cabin in the woods Jonny Browne/Shutterstock

Are those creaks the steps of old Kris Kringle on your roof, or, more likely, a major snow dump? Hmm, is your roof capable of handling the snow load of a heavy snowfall? 

If built to code, cottage roofs are designed to handle a one-in-50-year snow load, says Karl Korpela, the chief building official for the Municipality of Dysart et al., Ont. Based on historical snowfall data, a one-in-50-year snow load is the largest dump of snow a region is expected to get, says Korpela.

This data varies by region and is used by municipalities to regulate roof strength. For example, Toronto’s roofs are designed to withstand 18.75 pounds per square foot of snow while Haliburton’s can handle 41.7. “This means that one square foot of roof will support 41.7 pounds of snow,” says Korpela. (Keep in mind that wet snow is heavier; once snow becomes moistened and compacted, the weight increases significantly.) 

No matter how strong your roof is, it’s a good idea to give it some relief. “Shovelling off is definitely the only real way to do it,” Korpela says. He warns, however, against unloading snow unevenly. “If you start taking snow off one side, now you have all this snow weight on the other side, which the roof isn’t built to handle.”  

But, there’s an “if,” and it’s a big one. “If your cottage was built before 1975, there were really no strict building requirements,” Korpela says. “Cottages were built with weaker roofs, so those types of roofs should be shovelled off consistently.”

This article was originally published in the Winter 2019 issue of Cottage Life.

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