The Dreaded Ice Dams

Ice Dams


You can help prevent serious damage to both the roof and inside of your home by minimizing the likelihood that ice dams will develop, and by removing one as soon as you spot it. Ice dams can form when water from melting snow re-freezes at the edge of your roofline. Without roof snow removal, an ice dam may grow large enough to prevent water from draining off the roof. This water can then back up underneath roof shingles and make its way into your home.

How to Help Prevent Ice Dams from Forming:

  • Remove snow from your roof after every storm. To begin with, use a roof rake to clear snow from the edge of your roof upwards of three to four feet immediately after each storm. In addition to helping prevent an ice dam from forming, this will lessen the stress on your home’s roof. The amount of snow and ice your roof can support will depend on a number of factors, including the roof type and the age and condition of the structure. But a good rule to keep in mind is if more than a foot of heavy, wet snow and ice has accumulated on your roof, you should have it removed.
  • Clear downspouts. An easy way to help snow and ice drain off your roof is to make sure the area around your downspouts is clear. This can help prevent standing water from collecting near the gutter downspout.

How Do You Know if You Have Ice Dams?

  • Look carefully at the icicles around the exterior of your house. If they are confined to the gutters and there is no water trapped behind them, then an ice dam has likely not formed. Nonetheless, icicles can pose a danger to people when they fall off, so try to safely knock them down while standing on the ground, making sure not to stand directly beneath them. If you cannot safely reach them from the ground, consider hiring a contractor to help.
  • Check for water stains or moisture in the attic or around the tops of exterior walls on the top floor of your house. Stains and moisture may indicate that an ice dam has formed and water has penetrated the roof membrane.

How to Remove Ice Dams:

  • Melt the ice dams. Fill a nylon stocking with calcium chloride ice melt, and place it vertically across the ice dam so that it melts a channel through the dam. If you try this, make sure you can safely position the ice melt on your roof, and make sure to use calcium chloride, not rock salt. Rock salt will damage your roof. Also, be aware that shrubbery and plants near the gutters or downspouts may be damaged.
  • Get professional help. If you cannot safely reach the roof, avoid using a ladder in snowy and icy conditions. Consider hiring a contractor to remove the ice dam.

Long-term Tips for Preventing Ice Dams:

  • Insulate your attic. Make sure your attic is well insulated to help prevent the melting-and-freezing cycle that causes ice dams to form. Check and seal places where warm air could leak from your house to the attic, including vent pipes, exhaust fans, chimneys, attic hatches and light fixtures.
  • Install a water-repellent membrane. When replacing a roof, make sure to install a water repellent membrane underneath the shingles. This acts as an extra barrier that helps prevent water from seeping inside the building.

Ice Dam Prevention

Claims are no fun.

One of the most common and repetitive causes of property damage to building interiors is water damage resulting from the formation of ice dams on roofs.

An ice dam is a ridge of ice that forms at the edge of a roof and prevents the water produced by melting snow from draining off the roof.

The water that backs up behind the dam can leak into a home causing damage to walls, ceilings, and insulation.

While ice dams can develop as a result of multiple factors, the most fundamental causes are:

  • Heat leakage from the interior of the building into attic or loft areas that warms the middle and upper areas of roof decks (see causes of heat leakage below).
  • Snow accumulation on the roof surface which provides the potential for snow melt and re-freezing in the form of an ice dam. This problem can be amplified by lower pitched roofs.
  • Sustained exterior temperatures below 32 degrees which creates conditions under which snow melt water will re-freeze at the eave level of the roof.

Heat leakage can result from any number of factors common to residential properties:

  • An insufficient layer of insulation in the ceiling assembly below the attic or loft area as well as un-insulated or poorly insulated exterior walls.
  • Improperly insulated recessed ceiling lighting fixtures.
  • Improperly sealed and insulated ventilation fans, heating and air conditioning ducts and plumbing vent stacks.

Strategies for avoiding water damage from ice dams take two forms; those that are intended to prevent the formation of ice dams and those that are designed to provide a reliable means for roof surface snow melt water to drain off the roof to prevent water accumulation behind the ice dam.

Prevent the Formation of Ice Dams
  • Provide soffit and ridge ventilation to create and sustain a flow of cold air along the bottom surface of the roof deck.
  • Increase the thickness of insulation in the ceiling assembly below the attic or loft area.