Ice that forms at the bottom of a sloping roof is generally caused to a ventilation or insulation problem in the attic. The problem is that a dam of ice forms at the bottom of the slope, and restricts water evacuation, which means that stagnant water remains on the shingles, which are not at all designed for that.
Continuous cycles of thawing and freezing of melting snow creates ice dams:
- Ice forms while the snow is melting on the roof’s surface
- The water flows under the snow, and freezes again at the edge of the roof, creating a dam
- More snow melts, creating a puddle up against the dam ,and often moving the water back up under the shingles
Consequently, this problem often causes infiltrations.
What to Do?
Obviously, when repairing your shingles membrane, you should notify your roofer so that the situation can be corrected.
In the meantime, if ice dams are causing infiltrations, you can install heating cables, which are sold in big box stores and are easy to install. These cables remain constantly warm enough to melt the snow and ice, always leaving room for the water to evacuate. Note that some time is required (a few hours).
Also, if you’re looking for an efficient short-term fix, make a few grooves with an ecological melting agent, in order to allow the accumulated water to evacuate more quickly.
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Published December 6, 2013