Thursday, January 31, 2008

Ice Dams cause damage and methods to prevent ice dams in the winter

Ice Dams on your roof will create Ice Damage

An ice dam is a ridge of ice that builds up along the edge of a roof. The ice creates a dam that backs water up and under the roof shingles. Once the water is deep enough, it penetrates the roofing system and creates water damage inside the home.

Beneath the ice dam, undetectable damage is occurring in the attic and wall cavities. The wood framing is wet and may be rotting , insulation is soaked – which makes it inefficient and mildew and mould can grow in hidden spots causing odours and other problem inside the home.
Soaked framing and insulation will take a long time to dry out and will continue to contribute to wall damage and interior moisture problems. Uncorrected, the water can cause serious structural damage.

Once the ice dam is high enough to overcome the pitch of the roof, water seeps under asphalt shingles. The alternate freezing and thawing that occurs under these conditions can increase the magnitude of roof leaks. Once the water has penetrated the singles, it flows under the siding and eaves and leaks through the framing into your home.

To prevent ice dams, eliminate heat build-up in the attic space below the roof deck by:

• Improving insulation - Add insulation to improve the thermal envelope and slow heat transfer to the attic. Surfaces between the attic and the heated living space should be insulated to R-38 or more. As a homebuyer, you have recently been crunching the numbers, negotiating offers, adding up closing costs, shopping for mortgages and trying to get the best deals. Do not stop now. Do not let your real estate agent, a patty-cake inspector or anyone else talk you into skimping here.

• Stopping air "bypass" - Seal any opening that allows heated air to "bypass" the insulation and rise into the attic. The warm air in your home will always try to rise and will push through any small opening. The attic door should be weather-stripped even better than an exterior door. Exhaust fans should not empty into the attic and the area between the frame of the fan and the ceiling should be tightly sealed.

• Increasing attic ventilation will cool the space and remove unwanted moisture. The temperature in the attic space should be nearly the same as the outside temperature. When fixing attic insulation, avoid blocking any vents with insulation. The best ventilation system is balanced between low in-take from the overhangs and high-exhaust vents on the attic roof.

Read home maintenance tips

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A. Mark Argentino
P. Eng. Broker
Specializing in Residential & Investment Real Estate

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  1. This is an important thing for people to think about and I'm glad you mentioned it. Here in Collingwood, many people, especially our seasonal residents, use heating cables to avoid ice damming. It works well.

  2. Hi Marg,

    Yes, I would think in your neck of the woods, ice, snow, sleet and cold are everyday words for about 4 months of the year!

    Enjoy your weekend,