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The least likely cause of ice dams in Minnesota is the most likely cause on Flagstaff homes.

I’ve sold more than one Flagstaff home that had leaks caused by ice dams. Now is the time to do something about them – don’t wait until you see the leak! I found this interesting, somewhat academic article from the University of Minnesota, creatively entitled Ice Dams. Here is the crux: “The snow on a roof surface that is above 32°F will melt. As water flows down the roof it reaches the portion of the roof that is below 32°F and freezes. Voila!—an ice dam.”

Ice on roof of Flagstaff home

When the article discusses cause, you can tell they are from Minnesota and not Flagstaff, Arizona: “Since most ice dams form at the edge of the roof, there is obviously a heat source warming the roof elsewhere. This heat is primarily coming from the house. In rare instances solar heat gain may cause these temperature differences.” In contrast, solar heat is the most common cause of ice dams in Flagstaff! We have very cold nights and warm, sunny days that cause the ice and snow on roofs to melt. If that melt has not been able to flow freely off the roof – usually because of a clogged gutter – ice forms as the temperatures cool in the evening and lift the edges of the roof shingles, pushing ice and, the next day water, into interior walls. Dangerous and damaging mold is likely to follow. You may not see the leak inside for a long time.

What to do? Clear your gutters well before it snows. But even then, ice can build up where roofs meet at different angles on your home (take a look at mine, pictured here). Heat tape installed along the roof line or in gutters can help. Simply clearing the snow away also works – but that can be dangerous on winter days with ice under foot. Some Flagstaff painting companies turn themselves into ice-dam removers at the peak of the winter season – if you get desperate, give your friendly painter a call. They aren’t doing much outside painting in winter months and they have tall ladders and daring young men. Caution whomever you hire to not scrape all the way down to the shingles — you don’t want them damaged!

University of Minnesota Extension tells all about ice dams — almost.