How Ice Dams Form

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An ice dam forms when snow on a roof melts unevenly. Heat escaping from the attic warms the upper portion of the roof, causing snow to melt. That melted water flows downward, but when it reaches the colder eaves near the gutter line, it refreezes. Over time, that refrozen water builds up into a ridge of ice. “That ridge acts like a dam,” explains Veinott. “Water from melting snow behind it has nowhere to go. Instead of draining off the roof, it backs up under the shingles. Shingles, even perfectly installed, are not meant to be submerged under water.”
 

Once water gets beneath shingles, it can penetrate the roof deck and leak into insulation, ceilings, walls, and even electrical systems.
 

Homeowners often notice:
- Water stains on ceilings
- Peeling paint or bubbling drywall
- Mold growth
- Insulation saturation
- Interior dripping during freeze-thaw cycles
 

And in many cases, insurance claims are complicated or denied if the damage is considered preventable maintenance rather than sudden storm damage.