Dissolving Ice on a Roof With Calcium Carbonate

Ice and Snow on Your Roof

• According to the Canadian Mortgage and Housing Corporation, most roofs can safely hold about 8 inches of solid ice, up to 30 inches of fresh, light snow, or up to 17 inches of hardened snow. But if there is a combination of these, such as 6 inches of ice and a layer of fresh snow, the load may be too much for the roof to handle. Removing the snow can help, but often the ice adds the most stress to your roof. To determine how much ice is actually on your roof, pour hot water in one spot. If it melts to create a small bowl that holds water, you probably have a layer of hard ice. If it cuts through to the roof, it is probably hardened snow.

About Calcium Carbonate

• Calcium carbonate is a primary ingredient in calcium magnesium acetate, or CMA, ice melt, which also contains magnesium carbonate and acetic acid. It works better as a preventive measure against reicing than as a way of removing ice, but it can help remove large blocks of ice if applied repeatedly. Calcium carbonate is more commonly used as chalk, but there are several other forms as well. For example, calcium carbonate in a more compacted form is called limestone. When limestone is recrystallized under heat and high pressure, it forms marble.

Using Calcium Carbonate to Dissolve Ice

• To remove ice on your roof using ice melt such as CMA, first remove the snow that is covering the ice. This allows the ice melt to act on the ice rather than having to melt through the snow first. You can remove the snow using a snow shovel on a flat roof or a roof rake on a sloped roof. Work from the top down on sloped areas and from the center out on flat surfaces. Do not try to chip ice away. Once you have removed the snow, apply CMA ice melt in a path 1/4 inch deep by 3 inches wide starting from each corner and working along the edge and around chimneys and skylights. Apply in depressions behind ice dams or large chunks of ice to detach them from the roofing material. Avoid using too much ice melt; it’s better to repeat application than to apply too much. and over-application won’t melt the ice faster. Repeat as temperatures fluctuate to keep the drainage paths open on sloped roofs and to prevent reicing on flat roofs.

What to Avoid

• You should not use Ice melts that contain oxidizing agents such as sodium chloride or calcium chloride on your roof. These agents speed up corrosion and rust on metal roofs and gutter systems, and they can cause rapid deterioration of other roofing materials. Calcium magnesium acetate ice melt, which contains calcium carbonate, will not damage most roof materials and is safe for use around vegetation. While it won’t melt ice as rapidly as other materials, calcium carbonate-based ice melts can help detach large blocks of ice from your roof, preventing damage that can occur if you try to chip it away.