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.