Preventing Ice Dams

Icicles may look beautiful; however, they can pull off gutters, loosen shingles, and cause water to back up into your house. The same conditions that produce icicles, snow-covered roofs, and freezing weather, can also lead to ice dams; thick ridges of solid ice that build up along the eaves.

Gutters do not cause ice dams, yet gutters do help to concentrate ice and water in the vulnerable area at the edge of the roof. In addition to the physical damage caused by ice damming, you may be incurring exorbitant heating bills caused by the heat escaping through your roof from poor insulation or leaks. Understanding the lifecycle of an ice dam will help you fix or prevent them altogether.

Photo credit: GAF

Ice dams form when there is snow on the roof, and indoor heating rises through the ceiling into the attic from insufficient or deteriorated attic insulation and warms the roof surface, except at the eaves. Snow on the heated portion of the roof melts and flows down until it meets the section of the roof below freezing.

At that point, the water accumulates at the eaves and freezes into an ice dam. Further melting snow will back up behind the ice dam preventing it from draining and, as it lies on the roof, will work its way under the roof covering and flow into the attic. From there, it can leak into your home through insulation, ceilings, walls, and other areas causing soggy insulation, sagging and stained ceilings, peeling paint, and warped floors.

If ice damming has already formed, there are several quick fixes such as deicing with a heated cable or calcium chloride (never use rock salt), raking the snow off your roof using a long-handled aluminum roof rake, or using a fan in your attic, aim it at the underside of your roof where the water is actively leaking in to freeze the water in its tracks. While these quick fixes may lessen the symptoms, they do not treat the underlying problem.

Photo credit: GAF

Unless your roof is in poor condition and in need of a replacement, ice dams can be prevented by controlling the heat loss from your home with proper insulation, ventilation, and waterproofing shingle underlayment. If you are planning a roof replacement, this is the ideal time to take the preventative measures needed to eliminate ice dams.

Ventilation: Attic ventilation draws in cold outdoor air and drives out warmer attic air, cooling the attic and the roof in the process. A properly designed ventilation system must have both intake vents in the soffit or in the eaves at the lower part of the attic, as well as exhaust ventilation, such as ridge vents, high in the attic at or near the ridge. Baffles are placed at the eaves to maintain a clear path for the airflow from the soffit vents. It’s imperative to exhaust to the outside through your roof or walls, never through a soffit. Once heated air gets into your attic, it will warm the roof and contribute significantly to ice dams.

Waterproofing underlayment: Waterproofing underlayment, such as ice and water seal are laid across the roof (before roof shingles are applied) under metal flashing and counter flashing at roof penetrations and sidewalls, in areas where roof pitches change, in valleys and around chimneys, and along the eaves. It is completely resistant to water and a critical line of defense against leaks wherever it’s applied. Most ice and water seal underlayment’s are warranted against leaks from dams that do form on the roof. Shingle underlayment does not prevent the formation of ice dams; however, it will prevent backed up water from getting into the house. For existing roofs, waterproofing underlayment is only an option if you remove the existing roofing.

The key takeaway is to remember that preventing ice dams is entirely about keeping your attic space dry, well vented and the roof cold.

Taking these preventative measures now is the best way to keep ice dams from forming and maintain proper conditions on the roof deck:

Photo credit: Yuko Shimizu
  • Maintaining a consistent attic temperature.
  • Increasing ventilation with ridge and soffit vents. (1)
  • Seal/covering your attic hatch. (2)
  • Exhaust to the outside through your roof or walls, never through a soffit. (3)
  • Adding the recommended amount of insulation. (4)
  • Proper flashing around your chimney. (6)
  • Seal and insulate ducts. (5, 7, 8)
  • It’s important to note these preventative measures will only be effective if your roof is in good condition. Otherwise, a roof replacement will be necessary.

If you notice icicles forming along your eaves or signs of a roof leak, contact the experts at National Contractors, Inc. for an inspection and repairs.

For nearly 30 years, our family-owned business has been providing our customers with unparalleled quality and craftsmanship, exceptional customer service, and guaranteed satisfaction. National Contractors, Inc. has been a multi-chapter member of Community Associations Institute for 20 years, with staff that has earned CAI's Education Business Partner distinction. We proudly serve NJ, PA, DE, and MD.

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