How much of my roof do I need to clear of snow in order to prevent ice damming?
I was told 3 feet at one point but now I can't find the source.
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I'm not clear on what "3 feet" means; less than 3 feet deep? 3 feet from the edge? To be safe, you need to keep all three of your feet firmly on the roof? (Some details, and perhaps a diagram or picture, would help.)– Daniel GriscomCommented Mar 16, 2017 at 12:26
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1The question asks "how much of my roof do I need to clear", so 3 feet refers to roof exposure.– isherwoodCommented Mar 16, 2017 at 12:36
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Have you had ice dam problems in the past?– Carl WitthoftCommented Mar 16, 2017 at 18:58
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1 Answer
You didn't find a correct answer because there is no correct answer, just like there's no correct answer to "how much does a car cost?", or "what should I feed my pet badger?". It depends on several things, so you may need to rely on common sense and trial-and-error.
- Your climate (typical temperature range)
- Your weather (recent temperatures, sunlight, and snowfall amounts)
- Your home's architectural type (roof slope, truss heel design)
- Your home's roofing type and age (Does it have water barrier membrane underneath? How far up the slope?)
- Your home's sun exposure
- Your attic's insulation level
- Your attic's ventilation level
You can tell if you've done enough when there's no ice forming below the lower edge of the remaining snow on days when the snow on the ground isn't melting. If the snow on your roof is melting off in that case, it's because there's significant heat escaping your home that's not being ventilated away. That's the source of the problem.
Oh, and it's perfectly possible that the answer is "zero feet".
answered Mar 16, 2017 at 12:31
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Not sure I completely agree. Once you've cleared some roof, solar absorption on the bare shingles will lead to melting & some ice below the remaining snow line. Commented Mar 16, 2017 at 18:58
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If the bare shingles warm up, any water that runs down from the snow will not re-freeze on the roof... at least not in the heat/cool cycle at the wall line that leads to ice dams. In my experience it tends to dry off nicely, and in the evening any remaining meltwater mostly dries up as things cool down. Commented Mar 16, 2017 at 19:05
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you don't live in a cold enough place :-) . Usually what you say works, but New England's rather famous for sudden drastic temperature changes. Commented Mar 17, 2017 at 12:35
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