Snow and ice dam clinging to rooftop outdoors on sunny day, with icicles hanging down.

How to Prevent Ice Dams and What to Do If You Have One

What is ice damming and why should you prevent it from happening in your home? 

Ice dams are a problem that forms at the edge of a roof. Water from melting snow runs downward from warmer parts of the roof and freezes as it reaches the cold lower edge. 

The ice and snow start to form a crest. The snow on top of this crest can begin to freeze, and ice starts to form on the roof behind the crest. This buildup of snow and ice creates an ice dam. 

Homeowners should perform some maintenance to prevent ice dams to avoid mold and mildew, as well as water damage to insulation, roof decking, walls, and ceilings.

Two of the three conditions that can lead to ice damming are warm temperatures escaping through the roof and snow accumulation. In addition to having high under-roof temperatures, the temperature outside is typically between 22 and 30 degrees F. If these conditions are met, then ice dams may occur.

The third condition that can lead to ice damming is a poorly insulated attic. A well-insulated attic will help keep the surface temperature of your roof more consistent and uniform. This limits the roof from heating up in some areas and melting the snow while the air temperature is below freezing.

User: Herzi Pinki, CC BY-SA 3.0 <>, via Wikimedia Commons

One of the best ways to prevent ice damming is to install insulation, seal air leaks, and fix any other problems associated with your home’s roof ahead of winter.

Another way to limit the formation of roof ice dams is to provide good ventilation. The lack of proper ventilation can also contribute to ice accumulation on the roof and can lead to damage. Whether the problem is caused by a lack of ventilation or poor insulation, it’s important to get the professional help you need to stop ice damming on your roof before it becomes worse.

Please note that this is very important–You should never pour hot water onto an ice dam as this may cause damage to your roof or the shingles of your home. With that being understood, here are 3 tips on how to remove ice dams from roofs.

If an ice dam has started to form, you will need to do some roof snow removal. In some situations, a push broom and a roof rake may be used. However, care should be used as you may inadvertently harm the roofing materials. 

If you’re concerned with the re-freezing of an existing ice dam, use caution when removing snow that is close to the edge of the roof. This area can be unstable and dangerous. But if it’s safe to do so, use a roof rake to pull down the snow and ice and prevent it from re-freezing.

Man removing snow from a garage roof with a roof rake.

Another way to remove and prevent ice dams is by using a combination of crushed rock salt and calcium chloride on your roof. These chemicals will prevent snow from sticking, even when temperatures drop below zero degrees Fahrenheit. Home Depot sells a product called Roofmelt.

If you have an emergency with water leaking into your home you can dig out canals to act as passages through the ice dam. This can channel the water to drain off the roof. Remember to start at the bottom of the roof ice dam and work your way upward. However, it is safer to call an expert roofing contractor in an emergency situation.

If your roof sustains damage, call a pro. If the problem is small and requires simple repairs, you can do it yourself if you prefer. If you are unsure about what to do next, though, call in the pros. The last thing you want to do is make a repair job worse. Ice damming can be dangerous, so don’t risk it.

Many preventative measures for ice dams are simple and cost-effective. All you need to do is learn what causes them, how to prevent ice dams, and decide which preventative measure(s) you’d like to take. This should stop ice damming on your roof throughout the rest of the winter season.

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