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Winter threat: Ice dams

Updated: 02/22/2019

This month has been one for the history books with record-breaking snow totals covering Shakopee in a blanket of white. However, the heavy snow poses more of a risk than a backache. It can lead to ice dams and roof damage resulting in thousands of dollars in repairs.

An ice dam is a ridge of ice that forms at the edge of a roof, preventing melting snow from draining off the roof. This causes water to back up behind the dam and leak under the roofing materials, staining the ceiling and walls and rotting roof boards. Ice dams are most likely found in older homes.

house ice damIce dams form when warm, moist indoor air heats a snow-covered roof, causing melt. However, due to below-freezing temperatures, lower portions of the roof do not melt, thus forming a dam. The main culprit of roof heating is unsealed space around electrical wiring or plumbing vents. This can allow moist indoor air to leak into an attic. This heat loss can also create frost on the roof’s interior, leading to rot or mold.

So how do you know if you have an ice dam problem? You may notice stained ceilings and walls. Dirty, dark insulation can also be a sign of an unsealed penetration. Icicles typically signal severe heat loss due to a lack of insulation. Another obvious culprit are thick icicles hanging from your eaves.

To deal with ice dams immediately, remove snow from the roof using a roof snow rake. By reducing the snow load on your house, it eliminates a major culprit of ice dams. Be care, however, as not to damage your roof with the rake. Never climb on your roof during the winter as the slippery conditions could lead to falls. If you're concerned about ice dams, we recommend calling roofing professionals who can safely remove the ice buildup.

To prevent ice dams in the long-term, it's important to seal air leakage paths between the house and attic space ensure your ceiling is airtight. Adequate insulation of the wall/roof connection and proper roof ventilation also help by allowing outdoor air to circulate from soffit vents to roof vents. Make sure your vents are clear of insulation, bird nests and other debris to keep the air flowing. Proper attic ventilation reduces the potential of ice dam problems, as well as air conditioning loss in the summer.

For more information, visit the University of Minnesota Extension Office’s website at