Canada Mortgage and Housing Corporation

Canada Mortgage and Housing Corporation

November 03, 2011 10:29 ET

Ice Dam Proof Your Attic-and Keep Water Out of Your Home in Winter!

OTTAWA, ONTARIO--(Marketwire - Nov. 3, 2011) - If you're like most people, you probably don't spend much time in the attic. In fact, the vast majority of Canadians go up to their attics only when dealing with a leaky roof or "animal intruders" like bats or squirrels.

During the winter however, attics are vulnerable to another problem: ice damming. Ice dams are accumulations of ice that become visible at the edge of your roof or in the gutters. The ice dam can actually extend up the roof for quite a distance as a thin slab of ice under the snow cover on your roof. Once they've set in, ice dams can cause water from melting snow to be trapped between this thin layer of ice and your shingles. From there, the melt water can work its way under your shingles and then seep into the attic and your home.

Houses more prone to ice dams often have major leakage of warm air from the home into the attic, inadequate insulation – or both. They also can have complicated roof shapes with many valleys and dormers that can accumulate more snow and ice than other parts of the roof. Complicated roof shapes can also funnel large amounts of snow melt water into small areas which can lead to larger ice dams or more serious leakage problems.

Common and potentially dangerous approaches to solving ice damming problems typically range from attaching electric cables to attacking the ice with an axe. However, each of these also comes with its own drawbacks and risks ranging from damaging your shingles, roof deck and eavestroughing to incurring serious injuries caused by slipping and falling off the roof or a ladder. They also do not solve the underlying cause of the ice damming problem.

Fortunately, there are more effective solutions to help you protect your roof, house and your health – and potentially save thousands of dollars in roof repairs. Depending on your roof and the age of your home, these solutions include:

  • Air sealing the attic floor between your house and the attic space.

  • Insulating your attic thoroughly with the best insulation you can afford.

  • When re-roofing, waterproof your roof by first placing a self-sealing membrane over the roof deck (extended up an adequate distance from the eaves) before the new shingles are installed.

By spending the time to fix the problem properly the first time, you'll help prevent ice damming from occurring.

For more information or a free copy of the "About Your House" fact sheet Attic Venting, Attic Moisture and Ice Dams and other fact sheets on owning, maintaining or renovating your home, visit our Web site at or call CMHC at 1-800-668-2642. For more than 65 years, Canada Mortgage and Housing Corporation (CMHC) has been Canada's national housing agency, and a source of objective, reliable housing information.

Contact Information

  • For story ideas or to access CMHC information
    CMHC Media Relations - National Office
    (613) 748-2799