Ice Dams: Prevention and Removal


What Are Ice Dams?

Ice dams occur when a snow-covered roof over the attic is warmer than the eaves - the overhang of a roof. If the roof is warm, it will cause the snow to melt and run under snow along the roof.

When the melted snow hits the cooler eaves, it freezes. As ice builds up on eaves, it eventually traps water behind it. The water backs up under shingles and finds its way through seams in the building paper and roof decking to enter the attic and living area. Wallpaper, plaster and paint surfaces may be damaged in the process.

Fortunately, there are several ways to remedy the problem.

How Do Ice Dams Begin?
(thanks to the University of Idaho)

Ice dams along eaves may cause considerable damage to the roof and inside walls of a house.
  1. Poorly insulated roofs are the chief cause of ice build-up on eaves.
  2. Ice forms when the snow melts off a warm roof, runs down to the eave line, and refreezes there. Ice prevents water from running off freely.
  3. If water backs up high enough, it may seep under shingles and down into the house. Sometimes it leaks through plaster walls and ceiling.
  4. Ice dams are usually a problem only on cold days when the roof is warmer than the eave overhang. On warm days the snow melts at the same rate on the eaves and water runs off freely.

To Prevent Ice Dams

  1. Insulate between the top floor ceiling and the attic, or along the underside of the eaves if the attic is used as living space. Insulation also will help cut fuel bills.
  2. Ventilate the attic through windows and louvers when insulation is added to the attic floor. This will help reduce moisture condensation in the attic.
  3. Use electric heating cables along the eaves if insulation or ventilation is not possible.
  4. Cables can be strung out along the edge of eaves. When plugged in, they will heat the area, melt any ice already formed and prevent further freezing when water drips off the roof.
    • Be sure cables are approved for the intended use by the Underwriters Laboratory.
    • Check with your electrician for correct installation.
  5. Do not use salt to melt snow or ice from roof.
    • Salt will rust nails, damage gutters and downspouts, and ruin next year's lawn

If Leaking Has Already Begun

  1. If you have an immediate problem with ice dams, you should remove the snow from the part of the roof directly above the ice dam.
    • This limits the amount of water that can collect behind the dam.
  2. Remove the snow using a roof rake, hoe or push broom.
    • Roof rakes have long handles that allow you to stay on the ground when clearing a single-story roof. You can purchase them at hardware stores.
  3. You'll need to get rid of the ice.
    • Avoid using sharp instruments, such as axes, to break channels through the ice. This is likely to cause roof and structure damage.
    • Hot water will melt the ice, but don't use so much that it causes more leaking.
  4. If the dams are bad, consider calling a local company to come to your house to remove the ice dams. Some roofing companies do this. Be sure that they are legitimate and insured.

Additional Information
Ask neighbors or co-workers for recommendations of any firms in your area who handle ice dams.