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What is an Ice Dam and How Can it Hurt your Roofing?

Ice dam can hurt roofing

An ice dam is ridge of ice that forms along the edge of a roof, creating a literal dam that prevents your roof from shedding water and snow. Ice dams can prevent snow from draining off of your Lancaster or Chester County home's roof as it melts. As the water rests at the edge of the ice dam it may leak through the roofing which can cause damage to your walls, insulation, ceilings, and more.

How Do Ice Dams Form?

Ice dams occur only when three conditions are in place: snow cover, freezing outside temperatures, and heat being lost through the roof. The snow at the top of your roof will melt because of the heat escaping from your home. As it runs down the roof, it comes, once again, to freezing temperatures. When it refreezes, you're left with an ice dam.

Although the primary cause of melting snow is your home losing heat, it can also happen because of sunlight. And it doesn't need to suddenly get warm out. With temperatures as low as 14° F outdoors and 23° F in the attic, enough sunlight can be transmitted through six inches of snow to cause it to start melting on the roof.

What Problems Can They Cause?

Ice dams are hugely problematic because they can cause water to leak through your roofing, which in turn can cause a host of other issues:

  • Rotting roof decking, exterior and interior walls, and framing.
  • Mold growth (which can in turn cause respiratory issues).
  • Damaged insulation.
    • Wet insulation won't work very well, and chronically wet insulation won't even decompress once it dries. Damaged insulation will allow more heat to escape, will lead to more ice dams, creating a vicious cycle.

All of these and more problems can have a huge negative effect on your Lancaster or Chester County home thanks to ice dams. So what can you do about it?

How Can You Prevent ice Dams?

There are some things you can do to ensure ice dams never form in the first place:

  1. Install a metal roof. You still might get ice formations, but water won't ever leak through. Snow and ice are also much more likely to slide off of metal than other forms of roofing.
  2. Make sure your Lancaster or Chester County home's attic is adequately sealed. If you can keep heat out of the attic, you'll see the whole problem go away.
  3. Move or elevate any exhaust systems near the top of the roof. They may be melting a lot of the snow.
  4. Get any snow off of your roof as soon as possible.


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If you've had trouble with an ice dam and your Lancaster or Chester County home's roofing is damaged in any way, call Diversified Roofing Co. at 717-442-8422, or complete our online request form.