What Causes Ice Dams On Michigan Roofs?
This post from Jason Channell about what causes ice dams on Michigan roofs is interesting. Every ones heard the term, but might not understand how it actually works.
What Causes Ice Dams On Michigan Roofs?
Every year I see Michigan homes damaged by ice dams. A lot of people have heard the term "ice dam," but don't really understand what it is, what it does, or how to prevent it.
An ice dam is, essentially, a ridge of ice that forms at the edge of a roof. It prevents melting snow from draining off the roof, causing water to back up behind the dam, move back up the roof, and leak into the house.
Here's the idea: We know snow melts when it is warmer than 32°F. And we understand from gravity that water will flow down the roof.
But the roof isn't a uniform temperature. When it is warmer at the top, snow will melt. As the water reaches the lower portions of the roof that are below 32°F, the water freezes into ice that acts like a dam. That dam grows as more snow melts and water travels down the roof. Water will eventually back up behind the ice dam and actually travels back up through the roof by a process called capillary action.
The water now finds cracks and openings in the exterior roof covering and flows upward, under the shingles and into the attic space.
Jason Channell
Diadem Property Inspections
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