Does Shoveling Your Roof Really Help?

Weight

• Roofs are made to bear only so much weight, and snow can be a lot heavier than you think. Even light fluffy dry snow weighs 3.12 pounds per cubic foot. Wet snow weighs up to 20.81 pounds per cubic foot. Even if your roof is just 50 feet by 25 feet, a relatively small roof, just 6 inches of wet snow weighs 50 times 25 divided by 2 times 20.81 pounds, or about 13,000 pounds. That’s 6 ½ tons. Even if it’s just 6 inches of light fluffy snow, your roof will still be carrying just shy of a full ton. If there’s any ice underneath that snow, the weight is a lot more. Ice weighs 57.25 pounds per cubic foot.

Long Term Roof Stress

• Obviously you won’t be able to shovel off your roof immediately after every snowfall. However, you should never carry more than half the amount of weight that your roof is rated to handle for longer than a week if you want to avoid damage to your roof.

Ice Dams

• The warmth in your attic provides you with another motivation to get that snow off the roof as fast as possible. As the warm air in your attic brushes up against the roof, it warms up the roof and melts some of the snow sitting on it. This causes the melt water to flow down to the edge of your roof. The roof eaves do not overhang the attic. Once out of contact with the warm attic air, the water freezes again, as ice. This ice builds up into what is called an ice dam. Further melt is unable to run off the roof, as it is blocked by the ice dam. Instead, it back up under the shingles. There it causes water damage and can lead to the growth of mold and mildew.

Roof Pitch

• Your need to shovel does not just depend on the amount of snow and the amount of water in the snow. It also depends on how steep your roof it. The steeper the roof, the less the percentage of the snow’s weight that pushes down on the roof. Additionally, steeper roofs tend to encourage snow to fall off more rapidly on its own. Flat roofs need to be shoveled off often, as they bear the full weight of snow, and easily form ice dams. Very steep roofs may not be need shoveling very often.