What’s an Ice Dam?

After all the snow we have gotten this week it’s the perfect time to talk about ice dams.

What is a Dam?  A barrier constructed to hold back water and raise it’s level.

What is ice? Frozen water.

Why do Ice Dams form on roofs?  Heat leaking from the interior of the house raises the temperature of the roof and melts snow, the snow then falls down the roof to the eaves and soffit area where it is colder and freezes into ice.  This ice blocks the water coming down behind it and causes a reservoir of water to grow. This water can then seep through the shingles and into the house causing a leak.  Roofing and shingles are not designed to retain water on top.  They are designed to shed and repel water down and off the roof.  Here is the “textbook” picture:

icedam.jpg

Ice Dams are most common on the northern side of houses and also at the bottom of a roof valley.  Roofs with low slopes and wide overhangs are more prone to damming.

A good inspector will recognize the signs of an ice dam even in the summer when it is warm.  Stains on the ceiling and in the attic are a common sign.

If your roof dams up it is not the end of the world, there are several different options to prevent future dams, such as:

  • Improving attic insulation and ventilation
  • Adding eave protection
  • Adding electric cables.

Those are long term solutions.  The shortest solution is a roof shovel.  Use a long one and be careful.  Don’t get up on the roof if you don’t have too.  This can cause unnecessary damage and a much bigger problem than the one you had before.

For more information visit: Knoxinspect.com

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