The University of Minnesota Extension has a diagram of how an ice dam forms.
The reason that the snow on a roof melts in the winter when the temperature is below freezing is almost always from heat escaping from the house through the roof. Well insulated houses are less at risk from ice dams.
If you have an ice dam, what can you do about it? Here's some immediate steps to stop the water getting into your house.
- Remove the snow from your roof. Using ladders in the ice and climbing on a snowy or icy roof is very dangerous. Use a roof rake or similar tool from the ground but be cautious of damaging shingles and other roofing materials.
- Make channels in the ice to let the water drain. Spraying with tap water on a warm day will melt and make a channel through the ice but this is a very short term solution.
- Have a professional ice removal company remove the ice from the gutters. Removing all the ice will last longer than making channels through the ice dam, but as soon as more snow melts the problem will gradually return. It's not cheap either - around $250 for removing ice from 10 feet of gutter is an average cost, and can be significantly more depending on how much ice there is, how high your roof is, and various other factors.
What can be done to cure water leaking into a house from an ice dam in Minneapolis/St. Paul? One of the best ways is to stop the snow melting, and that means to reduce the heat coming through the roof. According to the University of Minnesota Extension, making the ceiling below the attic airtight to prevent warm air getting into the attic is the most important preventative measure. Adding extra insulation in the attic will also help greatly. Pleasantly, this will also reduce your heating bills.
Still, some houses continue to suffer with ice dam formation, and more proactive methods like modifications to roofs and gutters, or heating systems for the roof, are necessary to prevent ice dams.
