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What is an “Ice Dam”?

As we’re facing another brutally cold winter here in the NorthEast many home owners have legitimate worries about show on their roofs and the formation of ice dams. What exactly is an ice dam and what can we do about it?

ice-dam

Here’s an extract from a GAF technical bulletin on the subject that explains the situation better than I can:

What is an ice dam?

An ice dam is a build-up of ice at the eave that may eventually back-up water under the shingles. When snow on the roof melts, the water travels down the roof and freezes when it passes over the unheated eave. As the water continues to flow, it becomes blocked by the newly formed “ice dam”. This water then freezes and the cycle continues. As more water freezes, it begins to back-up under the shingle tabs. As this continues further up the roof, the warmer attic space may prevent the water from freezing and this water may enter the house.

What precautions need to be taken?

There are 2 primary preventative measures that should be taken:
The first is to install a leak barrier such as StormGuard® or WeatherWatch® Leak Barrier. These impermeable membranes prevent water from entering through the roof deck and should be installed a min. of 24” beyond the “warm wall” of the house.

The second measure is proper ventilation. Heat, moisture and condensation build up under roof decks. GAF recommends a continuous, balanced soffit and ridge system that meets the FHA/HUD-1/300 rule that calls for 1 sq/ft. of net free ventilation per 300 sq. ft. of attic floor space. Adequate ventilation can lower the temperature of the attic, which will reduce the melting of snow of the roof surface.

If you have any questions please don’t hesitate to call George J Keller and Sons at 973-927-0963.

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