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Cause Of Ice Dams

Over the last few years the snow patterns seem to have changed throughout the country. The result has been severe ice dams that have plagued homeowners and caused roof damage. Many Insurance companies are now excluding Ice Dams from homeowner policies which only adds to the anxiety. What exactly are ice dams? How do they form? Can a homeowner do anything to stop them?

The answer is yes. There are preventative measures you can take as a homeowner to prevent and eliminate roof damage caused by ice dams. However, it is important to understand exactly how ice dams form in the first place. 

Wintry Buildup

Ice Dams generally form when the outdoor temperature is above 20 degrees and either the sun shines down warming the roof or the attic temperature is above freezing. When this happens, the warmer temperature of the shingles can cause the snow on the roof to melt. When the snowmelt runs down to the colder eaves, it refreezes. This is especially true if the temperature starts to drop again.

If this cycle repeats over several days, the ice builds up and forms a dam of ice which prevents exits for the water to drain. Behind that dam, water will start to pool into large ponds, and it can back up under the roof shingles and leak into the attic or along the exterior walls. This can quickly damage drywall and create mold and mildew problems.

The right weather conditions for ice dams are usually when outdoor air temperatures are in the low 20s (°F) for several days and there are several inches of snow on the roof.

Cross Section of Home and Ice Dams

Attic Moisture

Once water leaks into an attic, it can actually rot the wood. Extreme cases have occurred where the water invasion is so severe drywall begins to disintegrate and light fixtures to fail leading to repairs in the thousands of dollars.  This can be prevented with proper gutter treatments in place.

Moisture Damage in Attic and Walls

Things To Avoid

You may think the easiest fix is to try to break up that ice dam, but this is extremely dangerous and could cause more damage which could literally add thousands of dollars in roof repairs.

Here are some things to keep in mind:

  • Do not routinely remove snow from the roof or attempt to “chip away” the ice of an ice dam. It will likely lead to shingle damage.
  • Do not use salt or calcium chloride to melt snow on a roof. These chemicals are very corrosive and can shorten the life of metal gutters, downspouts and flashing's. Runoff that contains high concentrations of these chemicals can also damage nearby grass and plants.


Here are a few simple steps that can help prevent ice dams on the roof and condensation in an attic.

First, prevent warm, moist air inside your home from rising into the attic by appropriately insulating the attic’s floor.   Second, make sure your attic is properly ventilated.
Research shows keeping the attic air temperature below freezing when the outside air temperature is in the low 20's can reduce the occurrence of Ice Dams. Provide good attic ventilation to replace warm air in the attic with cold outside air.

When this is impossible, investigate ways to keep the ice from forming on the eave or in the gutters. It is estimated that 75% of all ice dams form in the gutter or on the very eave of a roof. There are several new products on the market that are relatively inexpensive that prevent and solve this problem. AWA IceBreaker, a heated gutter guard, has been proven to be an effective way to keep gutters clean in the spring, summer and fall. It will heat the gutters to keep the water flowing in the winter. For ice dams that form on the eave of the roof, IceArmour Heated Eave and Valley Panels are the best solution.

The goal is to keep your eaves heated all the way back to the wall line. The AWA IceBreaker is designed to provide adequate heat in the gutter and works well on overhangs up to 8”. In more extreme situations, the IceArmour Eave and Valley panels are designed to protect the valleys and overhangs over 8”. You can find more information about these products on this website.


Your ultimate goal is to keep the temperature of your roof and your eaves equal to each other in order to a) keep snow cold, and b) allow melted snow to flow away from your roof and not refreeze.