Ice Dams, Again!

We written about preventing ice dams in the past, but given the number of calls I’ve been getting recently, I thought I would write about it again.

Whenever someone calls with ice dam problems, my credibility initially depends on whether or not I was the one who provided the roof. I hear people tell me that the person who installed their roof probably did something wrong and the truth is, that even the best roof installations are no guarantee against ice dams. For a look at what is happening under the ice, check out buildingscience.com. http://www.buildingscience.com/documents/insights/bsi-046-dam-ice-dam

There are things that help prevent ice dams, and the key word is “help”. The reason is, all of these things can contribute to better performance against ice buildup and water intrusion- they just won’t guarantee against it for one simple reason; Roofs are constructed to shed water- not hold water. Ice dams create pools of water- and only pools are meant to contain water. Here is the list of things that will “help”:

  1. Install ice and water shield when your new roof is installed- as long as this is above the freeze line by 18″ (it is sold in 3 foot sections for this reason), when water penetrates the first layer of protection, it will stop water from entering under the shingles as long as the roofing nails self-sealed the way the product is supposed to work. Request Grace Brand ice and water barrier in your new roof- it is the best.

  2. Make sure the roof is well vented (unless you have a modern, foam insulated, non-vented assembly-see pic. below). Allowing a good flow of air will help keep the temperatures more consistent on the outside eve and where the heat starts to melt the ice.

  3. If you can- use metal roofing- because it has the best chance of sealing out water, and I don’t remember ever seeing water from ice dams make their way in.

The best prevention is removing the snow… if you remove the snow too late and the dam forms, you will still be susceptible to the water intruding on the next round. I know that many of you that found this article on our blog are probably frustrated because you want to know what you can do now! The best chance of hiring someone is to drive around and speak personally with the roofer. In our area right now even our roofer has put a message on his phone line that he is unable to take on anymore, and hopefully this will be helpful for the next round.

Example of non-vented assembly in Sherborn

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