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  • Writer's pictureEleven Exterior Inc

What is an Ice Dam?

Updated: Jun 28, 2023

Ice dam: a wall of ice build-up at the edge of the roof usually formed by melting snow from heated buildings and refreezing at the colder edges: This causes water pool formation behind the ice dam.

Ice dam on the roofline
Ice dam

After winter with snowfalls and cold temperatures, spring comes with unwelcoming water stains on the ceiling – The water pool formation behind the ice dam got trapped, creating the leakage into the property.


#1 What Causes Ice Dams?

Uneven roof surface temperatures.

Because hot air rises (convection) and accumulates at the top (attic), snow cover outside the roof melts and flows down to the lower edges, or overhangs (eaves) that are exposed to cold air. Snowmelt now refreezes to form the ice dam. There are many hot spots exists on the roof (air leakage, exhaust systems, and chimneys) that contributes to build-up of ice dams.

The ice dam continues to grow as snow cover above it melts and feed itself until it reaches to the point where the roof temperature is above the freezing temperature, 32°F. Even though the dam growth is stopped, the snowmelt is still flowing down to the dam making a water pool. The accumulated water leaks through roof coverings, cracks, and any other openings. As a result, you see the stain in the ceiling.

If you see water stains on the ceiling, contact Eleven Exterior, Inc. for a free inspection.

#2 Proper Attic Ventilation, Insulation, and Ice & Water Barriers.

Icicles dangling from rooftops may actually signal potential ice dams in regions hit hard during winter.

It is best to prevent ice dams from forming by keeping consistent roof surface temperature. It may seem intuitive that removing snow will prevent forming ice dams and further water flows. This is only a temporary measure; the next snowfall will rebuild the ice dam. Climb on a roof might also be slippery and dangerous, even a minor fall. Eliminating the underlying cause will solve the problem permanently. The key? Temperature distribution.

Again, ice dam forms when there is hot spots on the roof melting snow and cold spots refreezes the snowmelt. There are many ways to achieve this:

  • Properly ventilating the attic.

  • Adequately insulating the attic.

  • Sealing cracks and other unwanted roof openings.

Additionally, roofing contractors can install an additional layer of underlayments with ice and water barriers to keep the property from the water damage.


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