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Fire & Water - Cleanup & Restoration

Getting To Know Ice Dams

12/10/2020 (Permalink)

One of the major causes of property damage during the winter months in New England are ice dams. Ice dams form on the eaves of sloped roofs. Freezing of melted snow at the eave impedes the drainage of melt-water, adding to the ice dam an so on. Because the drainage of the melt-water is impeded water may find its way under protective roofing materials and into the building.

How They Occur

Ice dams occur on heated buildings with sloping roofs in cold climates with deep snow accumulation. Ice dams on roofs form when accumulated snow forms an insulating layer under cold conditions that would cause the freezing point to be within the snow layer, if it were not subject to melting. Instead, building heat coming through the roof's surface melts the snow resting on it. This causes melt-water to flow down the roof, until it reaches below a place on the roof's surface that is below freezing—typically at the eaves where there is no building heat. When the melt-water reaches the frozen surface, ice accumulates, growing a barrier that impedes further passage of melt-water off the roof. Ice dams may result in leaks through the roofing material, possibly resulting in damaged ceilings, walls, roof structure and insulation, damage or injury when the ice dam falls off or from attempts to remove ice dams.

The melting of roof snow comes from the combination of three basic causes:

  1. Air temperatures well below freezing.
  2. A thick layer of dry snow, which has good insulating capabilities.
  3. Heat from the building coming through the roof.

Generally, ice dams occur when the under-roof temperature is above 30 °F (−1 °C) and the outdoor air temperature is below 22 °F (−6 °C).

Factors Of Increased Risk

While ice dams simply need the ideal weather conditions to form there are additional factors that will increase the likelihood of ice dams forming. They are:

  1. Old/damaged roofs
  2. Lack of or improperly installed rubberized asphalt underlayment 
  3. Damaged or blocked gutters
  4. Insufficient or improperly installed insulation

When ice dams form on your commercial or residential property;


  1. Clear all snow with a wheeled roof rake
  2. Place calcium chloride ice melt in panty hose, tie into small balls and place them in a row, approximately one foot apart, across the top of the ice dam
  3. If necessary us a rubber mallet to break the ice
  4. Hire a professional

Do Not

  1. Use a shovel to remove the snow
  2. Attempt to break the ice with a hammer or any hard object
  3. Use rock salts
  4. Any type of external heat source

If ice dams form on your commercial or residential property and cause water damage call the experts of SERVPRO of Foxborough at (508) 533-5305. We will make it, "Like it never even happened."

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