Am I likely to get an ice dam?

Old 12-06-06, 09:39 PM
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Question Am I likely to get an ice dam?

I am worried about ice dams. After the first frost of the season today, I saw that the about the first 12 inches of my roof, the entire way around, from the roof edge at the gutter upwards, was frost-free, but the rest of the roof above it was still frosted. I think this is because I have hotter internal air escaping up through the walls and out between the gap where the attic floor meets the walls below at the eaves (I have an old house, blown insulation in attic flooring to the 6" maximum depth of joists, probably very poor cavity wall insulation). As I understand it, ice dams form where the higher surface of the roof is hotter than the lower parts of the roof and melted snow from higher up refreezes at the lower parts. Should I therefore worry, or is it okay to think as the only part of the roof that it getting hot is the 12" from the roof edge upwards, any melted snow is going to run directly into the gutter and therefore be run off before forming any ice dam?
I am thinking of going round the entire attic and trying to push in some R-6 insulating material into any gaps between the tops of the house walls and the attic joists by the eaves. I assume this would be the sensible thing to do?
Thanks for any confirmation/guidance.
Old 12-07-06, 09:28 AM
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Ice dams do start from the bottom up. In most cases they are caused from snow or water running down the roof, reaching the gutter, freezing and backing up under the shingles. Sometimes it can back up a couple of feet. There are two solutions for this problem. The first is installing ice and frost on your roof, from the edge of the roof and upward to 3' above the edge of the roof. Most building codes require this when new roofs are installed. The other solution is hard. I see it done every year and still cannot believe it. That is removing the gutters so the water will run off the roof and down to the ground. This is usually done on ranch style homes. Here you go. Good Luck
Old 12-08-06, 07:09 AM
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Be careful shoving insulation along the edge of the attic - you don't want to block the air flow through the soffit vents into and out of the attic if you block that flow you will have more problems. Make sure there is a gap or use the baffles you can get at most box stores to leave a space for air flow.

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