The Effect of Snow-Load on your Roof

Category: General Published on Feb 14

Whether you know it or not, your roof can only withstand so much snowfall. Too much accumulation of snow on your roof can cause great damage, here are some basic things you should know in order to protect your roof from snow-loads.


The Impact of Snow Load on a Roof
Winter storms can have a direct effect on the condition and structure of your roof. It is important for homeowners to fully understand the signs of weather damage. When heavy snow accumulates on your roof, its weight causes stress to the roof, which over time weakens it altogether. Snow can also cause damage to your shingles by way of melting and then freezing again. When the snow melts, it allows moisture to get into the shingles, when it freezes again it expands causing great damage.

Ice Dams
Ice dams are created when the snow on your roof melts and before it drains freezes along the edge of your roof. When this happens it prevents water from running off your roof, eventually allowing it to find its way under the shingles and eventually into the house itself.

How Much Snow Can Your Roof Withstand?
Unless your roof structure is damaged or decayed, typically most residential roofs can support up to 20 pounds per square foot before becoming stressed.

Fresh Snow – 10 to 12 inches of new snow is equal to one inch of water, which is about 5 pounds per square foot. This means typically you could have up to 4 feet of snow accumulated on your roof before it becomes stressed at all.

Packed Snow – 3 to 5 inches of compacted snow is equal to one inch of water, which is about 5 pounds per square foot. This means typically anything over 2 feet of compacted or snow that been sitting for a while will cause stress to your roof.

If you combine these two you can end up with significant amounts of weight which is way past the capacity your roof can handle. Note: 1 inch of ice is equal to 1 foot of fresh snow.

Typically most snow storms will not bring you anywhere near these amounts of snow, but be careful in the events of snow fall on multiple days where it doesn’t have a chance to melt away. To have an idea of how much snow has accumulated on your roof is as simple as watching the weather for snow accumulation in your area. If you happen to have severe snow storms where these amounts of snow accumulate, contact a professional as soon as possible in order to have the snow removed.

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