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Question DetailsAsked on 3/5/2015

I get an ice dam as a result of the gutters filling with ice and backing up onto the roof. How can I prevent this?

Everything I read on the internet says it's due to poor ventilation in the attic. I only have a big problem on the side of the house facing the sun with gutters that get filled with ice. On the side away from the sun, there is only a small ice buildup. What do I need to do to prevent this next year?

If I need additional vents or better insulation, what would that typically cost (ballpark) for a 1500 sq ft house? The only area without soffit vents is around the garage, which is heated and insulated. Ridge vents are on all peaks of the house.

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2 Answers

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Guest, so you know you are dealing with an issue that is extremely hard to "cure" from happening. First, don't believe everything you read on the internet. Most of the "informative" sites have ulterior motives to sell something. Ice damming is caused by freeze thaw cycles. When snow and ice land or form on a roof, then thaw and freeze quickly. It is especially prevalent on homes with gutters because when the heated ice "water" rolls down the roof and into the non-heated gutters it freezes almost immediately. This builds up and forms a dam. The reason your the side of the house not facing the sun has less is because it melts slower and dissipates. All of the ventilation information on the internet is not wrong, I am not claiming that. Because home with a well insulated attic, will have a cooler roof, this will cause the snow to melt slower and the water that forms will have a longer time to disappear. It will also have snow on it for a much longer time. But, it will not guarantee that ice damming will not form. To my knowledge, if you install, heat cables in your gutters and downspouts is the only real solution that can guarantee the dam does not form.

Exterior Upgrader is owner of:

Euro-Tech, Inc.

Servicing much of Illinois and Wisconsin


Answered 5 years ago by ExteriorUpgrader


Do you have an overhang? If yes, which most will answer, does the ice dam form in the gutter or where the home transitions from having a heated area under it to the unheated overhang?

If the ice dam is strictly in the gutter does it cause a back up under the roof shingles causing water to leak inside your home? (FYI do you have a ice barrier under your shingles?) If no leakage, the ice dam is of no importance and ignore it. If yes try the heat cable in a zig zag pattern in the area (I like Menards 5 watt cable.) If the ice dam is further up the hill (at transition point) and causing a leak, time to consider lowering the attic temp. Lack of insulation (like around a canister light over kitchen sink) is a problem. Remove light bulb and spray non combustable expanding foam and reinstall light. If above a heat duct perhaps use a double bubble radiant barrier as shield above duct. Sometimes it can be an bathroom exhaust duct blowing into the lower part of the attic. Or contract with a spay foam company who will rake the old insulation back before insulating. Or most likely you do not have enough soffit ventilation to feed your ridge vent. Cut in vents & have protective shutes installed in attic to keep insulation from coving them.

Or you can install a heated gutter cover like MasterShield or LeafGuard

Jim Casper old energy conservation guru and gutter contractor


Answered 5 years ago by jccasper


Excellent responses ads usual from ExteriorUpgrader and JC.

What you could be experiencing, and sounds strongly like that because of the diffaerence on the two sides of the roof, is that you are seeing diurnal melting - melts some of the snow on the roof in the daytime, freezes at night - either on the lower portion of the roof or in the gutters.

If the icing is on the roof overhang and that area is snow free or melted back, so the leading edge of the snow is over the house but not on the overhang, then that commonly means your overhang is actually getting warmer in the daytime - commonly from solar heating on the house wall, that then rises and heats the underside of the roof overhang. This meltwater then runs into the gutter, and may freeze immediately if the outside air temp is below freezing, ormay run off in the daytime but freeze up and glacier either at the lower edge of the roof or in the gutter as it cools off at night.

Solutions - heat tape as described in other comments. Also, painting the gutters a dark color can facilitate daytime melting, as does using plastic gutters (I can hear JC screaming NOOOOO from here) which absorb solar energy better and do not radiate the gutter heat as fast in the afternoon/evening so melt out easier.

Another solution - sort of the "if you can't beat them, join them" school of thought: remove soffit covers somore wall heat goes up under the overhang and eave area, though this does result in a slightly warmer attic and roof. I have even had a few projects where painting the solar-facing wall a much darker, energy-absorbent color alleviated the overhang glaciering and ice damming issue. Of course, this is NOT a solution if summer heating from that wall will become a significant energy problem.

In some cases this promoting faster melting of the snow on the roof can aggravate the issue, in others where the thermal stability is more marginal it can heat the overhang enough to melt the icing and gutter ice in the daytime, so is a trial and error thing, but commonly helps on south and west facing walls UNLESS in an area whith constant heavy snow accumulation which you are never going to effectively melt away so you want the coolest roof possibele. Another solution in that case which is commonly seen on deep snow country cabins but rarely elsewhere is to install wider soffits, sloping up at say 30 degrees or so from the house siding to the back edge of the underside of the fascia, so most of the solar heated wall heat goes up the surface of the soffit to the bottom sigutters and heats them, with less convective air being forced into the soffit openings.

Another solution, assuming you are careful - and you do NOT have to go all the way down to the shingles - is shovelling the snow off the roof so it quickly goes snow-free, hence no source water for glaciering. If you do this, do NOT NOT NOT just clear the part on the overhag or just a ways above that with a roof rake - clear all the way to the top of the ridge - perhaps only in one area if glaciering is only occurring at say some vents and duct exits. The reason to not clear only partway up the roof is if you clear the bottom portion, that then become the frozen/melting boundary, and water from snow that melts in the daytime will keep filtering through the snow for hours, and start glaciering up at the lower edge of the snowpack. This location would usually be on the overhang where some possible minor ice damming might not cause damage if it leaks a nit - but now that "freezing front" is up on the field of the roof, where icing and glaciering at the edge of the snowpack can cause backup into the snowpack and ice damming water getting under your shingles, so if your water barrier is not flawless you then have a leak into the house rather than just through the overhang.

Answered 5 years ago by LCD

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