What Can Happen When Snow Sits on Your Roof?

Weight-Bearing Problems

• The weight of snow depends on its water content. A wet, heavy snow weighs much more than dry, light snow. A cubic foot of heavy, wet snow can weigh up to 20.81 pounds, according to the Thomson Slate Roofing site. Multiply this over the area of your roof, and you can see how much weight the roof must support under a heavy snow cover. This additional weight can cause roof collapse. Often collapse can occur when a heavy rain follows a winter snow storm, which can be a particular problem on flat roofs that do not allow the snow to fall down the roof angle. Roofs can begin to bow or sag, signaling stresses on the support structures. Remove heavy snow accumulations, especially on flat roofs.

Leaks

• Heavy accumulations of snow can damage the appearance of roofing shingles. These shingles are designed to shed water, not hold it, and when snow melt is obstructed, it will flow under shingles and over flashings to create leaks. Homeowners should consult with a roofing contractor to free the water flow from the roof areas.

Ice Dams

• Ice dams are a problem that occurs after periods of heavy snow. Ice dams are ridges of ice that form at the edge of roofs that will prevent the melting snow from draining off the roof. Ice dams have a relationship with the amount of heat that escapes from the roof area of the home. The snow melts and collects at the edge of the roof where the temperature is colder. The water then freezes, creating this ridge. Because this ridge blocks the water from falling from the roof, it finds cracks and openings that allow it to flow. Sometimes, these cracks lead into water leaking into home interiors. Removing snow from the roof prevents the formation of ice dams that can lead to damage of your home. Hosing with tap water on warmer days will help to create channels where water can flow off the roof, according to University of Minnesota professor Timothy Larson. Roofing professionals can also help to make channels to melt ice dams after heavy snowfalls.

Gutter Collapse

• When large amounts of snow begin to melt, the snow can turn to water and begin to fall into gutters, straining the fasteners that hold the gutters to the structure and causing them to collapse. During the warmer months, ensure that all gutters are secure, and perform repairs as needed before the winter months arrive.