How to keep heavy snow from damaging your roof
Snow can add the weight of a truck, or more, to your roof. Here's how to avoid experiencing a roof collapse after heavy snow.
Just 4 feet of snow can weigh as much as a dump truck on top of your house, but removing the snow can be just as dangerous.
When a major winter storm unfolds, home and business owners have more than just messy roads to worry about. Heavy snow can pose a serious risk to roofs and cause some to collapse.
AccuWeather meteorologists advise homeowners to hire contractors to remove snow or use snow rakes from the ground, if the roof is not too high.
MAMMOTH LAKES, CA - MARCH 21: A worker shovels snow from a roof at the Shilo Inn as it continues to deepen in the first days of spring on March 21, 2023 in Mammoth Lakes, California. Following the driest three-year stretch on record, a series of destructive, and sometimes deadly, atmospheric river storms has been sweeping over the state since early winter, bringing torrential rains, wide spread flooding and one of the snowiest winters on record in the Sierra Nevada Mountains. The extreme precipitation is bringing relief from years of drought conditions across much of the state, though experts warn that the extreme weather swings may worsen as climate change continues. (Photo by David McNew/Getty Images)
"When we're talking about feet and feet of snow, that weight can add up fast, and can lead to concerns around roof failures," AccuWeather Chief Meteorologist Jon Porter says.
The weight of snow on a roof is dependent on its water content. Wet snow weighs more than dry snow, and powdery snow can drift, adding uneven weight around rooftop units. The average is 5 pounds per square foot, according to Dr. Michael O'Rourke, a structural engineering expert. O'Rourke says that drifting snow is what causes 75 percent of roof failures.
When snow weighs less than 10 pounds per square foot, it is manageable, but concerns arise when it approaches 20 pounds per square foot. In the northeastern United States, roofs are generally designed to support 30 pounds per square foot, but some can support up to 100 pounds per square foot.
Snow compacts over time, maintaining its weight, even as it appears to lessen in depth. Rain can saturate and add weight to snowy rooftops. As temperatures rise, melting snow can refreeze around gutters and drains, trapping water and causing leaks and stress on the roof.
A roof has collapsed on a local business after recent storms dropped more than 100 inches of snow in the San Bernardino Mountains on March 6, 2023 in Crestline, California. (Gina Ferazzi/Los Angeles Times via Getty Images)
Different roof designs cope with snow differently. Sloped, or gable roofs, can face snow accumulation on one side due to wind, while shorter slopes may allow snow to blow off. However, sloped roofs can be prone to ice dams. Flat roofs, while not entirely flat, may allow snow to blow off easily. However, external systems on these roofs can encourage snow drifts. They are less prone to ice dams but can trap melting water if drainage systems freeze.
There is no ideal roof type to battle winter weather, as it depends on the type of snow and wind conditions.
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