An ice dam is an accumulation of ice at the lower edge of a sloped roof, usually at the gutter. When interior heat melts the snow on the roof, the water will run down and refreeze at the roof’s edge, where temperatures are much cooler. Eventually, the ice builds up and blocks water from draining off of the roof. This, in turn, forces the water under the roof covering and into your attic or down the inside walls of your house.
Once an ice dam forms, the potential damage can be serious. Take these steps now to avoid trouble later:
• Keep the attic well ventilated. The colder the attic, the less melting and refreezing on the roof.
• Keep the attic floor well insulated to minimize the amount of heat rising through the attic from within the house.
• When you re-roof, install a water-repellent membrane under your roof covering. Waterproofing shingle underlayment (ice and water shield) is a strategy to prevent water back up through the roofing materials, in addition to proper ventilation and sufficient insulation.
These approaches decreases the likelihood that ice dams will form or, at least, reduces their size.
Needless to say, such leaks are not caused by a shingle failure or defect. Thus, the leak is covered neither by the manufacturer’s warranty nor by the contractor’s workmanship warranty. Along with that, the resulting interior damage is typically covered by your insurance carrier, but not the prevention or removal of the ice dam.
Unfortunately, ice dams may be unavoidable if your home has recessed lighting near the roof. Heat generated from these lights melts snow, which then contributes to ice dam buildup. The only sure way to avoid this problem is to eliminate recessed light fixtures near the roof. In short, the causes of ice dams are many and complex. The likelihood that one will form is both unpredictable and highly weather-dependent.