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How Much Snow Can a Flat Roof Support?

J. Lang Wood

During the winter months, roofs also have to withstand the significant weight pressures from wet snow and ice. Gable and other roof styles that are constructed with angles can shed large amounts of snow as it gradually melts. Flat roofs, however, do not have angles to allow snow to slide off the roof structure as it melts. This inability to shed snow makes it important to calculate how much snow a flat roof can support without structural damage.

About Flat Roofs

Snow accumulation can cause a serious hazard to flat roof structures.

Flat roofs are exactly that, flat. They have no angles that aid in removing the snow from the surface. In addition, flat roofs can have low areas where water pools that can freeze and keep the snow in place, adding to the burden on the roof. Flat roofs are the most vulnerable to damage from heavy snows.

Snow Loads On Flat Roofs

The weight of snow is determined by how much water it contains. A cubic foot of dry snow can weigh from six to eight pounds, according to the WorldWeatherPost. Packed snow can weigh up to 20 pounds per cubic foot. The same volume of ice can weigh three times that amount. A roof designed for a 20 pounds per square foot snowload could hold up to four inches of ice. How long the flat roof must hold the weight is another factor in determining how much snow the roof can hold. You can calculate the likely amount of snow on your roof by determining how much has accumulated at ground level.

Removing Snow From Flat Roofs

It can be dangerous for homeowners to try to clean off their roof when it is slippery with snow and ice. A snow rake can help you to remove the snow from ground level. A leaf blower can help to blow off some of the snow that isn’t iced onto the surface. For a large amount of snowpack, the best idea is to hire a roofing contractor who knows the safe way to remove snow from flat roofs. It is well worth the money paid to protect your health and the structure of your home to have an experience professional take care of this task.

Signs of Roof Stress From Heavy Snow

A number of signs can alert to a problem with a heavy snow load on your flat roof. Leaks entering the interior of the home are telltale signs. A sagging roof signals that the load on the roof is reaching the optimal level of weight that the roof can withstand. Bends or ripples in support structures are other signs that too much weight is on the roof. Cracks in walls or masonry is another sign that load levels are too high for the structure, as well as bowed pipes or conduit. If you see any of these stress signs on your home, call a roofing contractor immediately to arrange for snow removal.