During winter, precipitation combined with freezing and thawing cycles can create ice conditions in and around gutters. Some homeowners use rock salt to break up these ice dams. But homeowners should take caution before doing this as salt can cause damage to the exterior of your home.

Why Ice Dams Occur

After a heavy snowfall and several days of sub-freezing temperatures, warm air inside a building or home can warm the underside of a roof, causing snow and ice on the roof to melt. The melted water can drain along the roof, under the snow, until it reaches the cold eve overhang. The eve overhang usually remains the same temperature as the outdoors, and the melted water will refreeze and form an ice dam.

Depending on the design of your home, ice dams may not be an issue, and allowing the ice to melt may be sufficient if you are not experiencing damage that warrants immediate action. Conversely, if water is leaking down the side of your house, then the decision process of what to do must be carefully evaluated.

There are five commonly used types of ice melt (also known as rock salt):

sodium chloride
magnesium chloride
calcium chloride
potassium chloride
acetates

Rock salt in all forms is corrosive. It can cause many kinds of damage including gutters, metal flashings and downspouts. It can also damage roofing and siding, and it can change the color of your shingles.

In addition, runoff from rock salt dissolved in rainwater can weaken or kill foundation plants, grasses, shrubs and the roots of perennial flowering plants. These harmful effects can be magnified if the salt product you use has a combination of chemicals in it, as is often the case.

Many ice melt products rely on sodium chloride. This is the type that can leave stains on a driveway and sidewalk, rust the underside of cars and destroy grass. It is also known to be dangerous to pets. Magnesium chloride is the type of salt that is generally thought to be less corrosive.

If you do decide to add rock salt to your gutters, choosing your ice melt product carefully and using it sparingly is advised. However, calling a professional is a best practice that can save many headaches from unintended home damage.