Ice Dams: What are They and How to Prevent Them

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Ice Dams: What are They and How to Prevent Them

Ice Dams: What are They and How to Prevent Them

If you live in a cold climate, you know how difficult the winter months can be on your home and property, and the many things you need to do to protect them. One of the most difficult problems, and potentially most costly, is the formation of an ice dam.

What is an Ice Dam?

Water that forms a ridge of ice at the edge of a roof, usually where it meets the gutter, is called an ice dam. When an ice dam forms, rain and melting snow can’t properly drain away from the roof. This can cause water to back up behind the ice dam, and eventually leak into the home.

How Do Ice Dams Form?

Ice dams are a pervasive and damaging winter roofing problem caused by poor roof ventilation and a warm attic space. Left untreated, ice dams can cause serious damage to your roof, gutters, paint, insulation, drywall, structure and even contribute to mold.

Ice dams form when melting snow on a roof runs off and refreezes at the edge of a roof. This condition occurs when the snow is melted by a warm roof, creating water running between the snow and the warm roof surface, then freezing and turning to ice when it gets past the exterior wall and hits a cold unheated roof edge or gutter. As the bottom of the snow pack continues to melt, water continues to flow down the roof surface until it hits the ice, thereby creating a larger and larger ice dam. Ironically, ice dams often occur after a very heavy snowfall, because snow, itself, is a great insulator.

How to Prevent Ice Dams

The absolute best way to prevent an ice dam is to make sure your roof is properly ventilated and that there are no heat sources in the attic itself.  Attic warming from poor ventilation is made worse with the introduction of heat from the occupied floor below the attic including sources such as lighting, air leaks, and ductwork.  Make sure you eliminate sources of heat, such as:

  • Uninsulated recessed ceiling can lights installed in the floor below
  • Poor attic floor insulation
  • Uninsulated folding attic stair openings
  • Heating ducts
  • Furnace or water heating equipment in the attic
  • Bathroom vent fans that improperly vent to the attic

Ice Dam Damage

If this situation continues, the ice can work its way back up the roof edge, get under shingles, melt and leak into the exterior wall, home or attic. Damage from ice dams may not be readily apparent. As the ice melts and possibly drips into the wall or attic, insulation can be become wet and lose its ability to perform properly. In some cases if the right temperature and humidity exist, mold may begin to grow in the attic. Often paint will peel or blister weeks or months after the ice dam has melted as moisture from the leaks in the wall or ceiling cavities tries to leave and pushes outward.

The most effective time to battle and win the war against ice dams is before winter. Here are some recommendations on how to beat ice dams:

  • Keep gutters clean
  • Eliminate or reduce direct sources of heat in the attic
  • Increase attic floor insulation
  • Properly ventilate roof, attic, and eaves

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