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Hi All,
This is the 4th season in my new old house and the last 3 have been quite mild for Maine. Very little snow to speak of. Well, this year snow has picked up.
The other day I noticed a very large ice dam on the north side running the whole length of the eave.
Its a bungalow style home , single story, unfinished attic. The only access is a hatch through a closet. The eaves have an overhang of about a foot to foot and 1/2 .
The attic floor has blown in cellulose between joists. Nothing in roof rafters. They are open to the roof boards.
I have never experienced ice dams before so I’m not sure what needs to be done to correct/eliminate the problem.
I plan to add some living space in the attic sometime in the future if that has any bearing of alternatives.
Any information would be greating appreciated!
Replies
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Hello Kevin,
Check out "Installing attic vent from inside" further down in the discussion. I got a lot of really great advice about ice dams on my house.
Good luck!
*I bought a roof rake a few years ago (plastic blade, $30) after major ice dams had water trickling down the interior walls of my house in Massachusetts. I spend 20 minutes clearing the eaves after each snowfall and the dams haven't returned since.Coincidence? Mild winters? I was in Maine after a snowstorm a few weeks ago and noticed two houses side by side -- one had been promptly raked, the other showed no signs of such attention. Guess which one had foot-high ice dams?
*We have had a nice winter so far in Maine, but I'm enjoying it more now that I replaced my roof structure last year... no more shoveling the roof after every storm :-)In addition to stopping heat flow into the attic, the key to elimination of ice dams is good ventilation of the underside of the roof deck.I like to use ridge vents at the peak of the roof with fully perforated eaves in vinyl or aluminum. More air flow, the better!I wonder if installing that pink raftermate stuff at the eaves would deflect enough leakage from the walls to slow down the ice?Cheers!Will
*Lars and Will cover the maintenance and construction options, respectively. Lars: it no coincidence that you have no dams since raking the roof. Without insulation (snow) over the shingles, the shingles are at the outside temperature. Either it is above freezing and then the snowmelt with run all the way off the roof. Or it is below freezing and then all the snow stays put. But if you leave the snow in place then heat from inside the house melts snow over the attic and the water runs down to the eaves. But the eaves (which recieve no heat from the house) are below freezing and the ice dam forms there.I agree with Will's points that 1) you want to not heat the roof and 2) ventilation under the roof sheathing removes that heat. Additionally I would note that there are products such as Water & Ice that are really sticky, sealing membranes designed to be a more waterproof layer at the eave/heated roof junction. People argue whether that is sufficient or not. I choose to have a vented, "cold roof" on my own house AND use two courses of Water & Ice. Belt and suspenders. Seems that during new construction, it will never be easier to spend a few bucks to avoid future problems. -David
*Thanks for all the info...It was very helpful.I spent a few hours in the attic space this past weekend.I took temp at floor level and it was almost the same temp as outside. Inside 38 degrees, outside roughly 38/40...I assume simply warming faster out than in during day.I did find that the bathroom exhaust fan was leaking some air and also noticed that sewer vent pipe race did have a section open all the was to the basement.I sealed the fan, insulated the fan vent pipe all the way to the exit point, went to the basement and stuffed some insulation around sewer vent pipe and also around chimney.How quickly can I expect to notice any change in icedam? Will I? Or do I need to attack the ice with a chainsaw??! (Just kidding on the chainsaw!)Also, is just a few degrees enough to cause the snow melt?
*I am in New Brunswick and we are having a good snow year as well. Here the temperature has not been above freezing and yet several houses are suffering from ice dams. The one next door is directly below the plumbing vent stack. I would bet that it is open to the interior as was yours. Other houses seem to suffer evenly along the whole roof so I would not want to guess how much hot air is getting into those attics.
*I'm in northern Michigan where we received 260 inches of snow this year. Preventing ice build-up means combining insulation with attic venting. I've got R-42 in my attic but will experience ice build-up on eaves when my roof and ridge vents are covered with a foot of snow or more. Last year I also installed gable vents so that I wouldn't have to shovel roof so often - they work fine. If you do not have adequate venting both in eaves and roof then you will be looking at ice. Insulation only slows down heat loss. Think I read somewhere that it would take 90+ inches of insulation to stop heat loss. Converting attic to living space is another animal entirely. If ceiling is not properly insulated and vented mucho ice will develop - is a common problem here. Most folks stuff 6" of insulation between the rafters and then drywall - then fight ice build-up and moisture damage from that day forward.
*As we have said many times over the last ten years the first line of defense against ice dams begins in the basement or crawlspace. GeneL
*Hi again...Thanks Gene...I did combat the areas of the basement that were obvious air leaks all the way to the attic.Several days after my work I did notice "shrinkage". They are all gone now...due mainly to the copious amounts of sun for 5 days straight.Wont really know for sure til next winter...but its a good start.
*Randy, if insulation and venting is so important please tell me why you have both and still get ice damming. Is this R-42 in fiberglass?My roof is only insulated to R-20 with sheet foam, and is damn near unvented and my roof makes no ice dams. I get icicles, but no ice extending up the roof more than one inch. This is because convective currents cannot get to my roof.I advised a client to block off his roof vents and his roof stopped melting snow! This was due to the fact that his vents were sucking tons of air out of the house because there were roof vents, but no soffit vents.If venting and high R-value were the answer, than Icynene would have been out of business a long time ago. They spray R-24 on unvented cathedral ceilings all over Canada. They have been doing this for 15 years, I think Canada may have had a "bad" winter or two in the last 15 years.I will say it again - roof venting is insurance, people put it in because they don't care to know the proper ways to eliminate the problem.-Rob
*I have a shed outside people it has no heat in it. It has an ice dam on the north side . Get the picture? Sometimes god has a little to do with it. You can get ice damming even with a great situation. If the temp was the same on inside as out then you should be fine. My bet is you had no leaks right? If snow is melting on the roof at 4:00 pm and at 6:00pm it begins to freeze you will get some ice build up , after two or three days you will have an ice dam regardless of insulation or not.
*Ron, Of course there are the rare few days of the year where this happens (ice dams on unheated roofs) but generally it is not a long term problem. It tends to be at the time of year when the daytime temps are above freezing and the nighttime temps are below freezing, and there are significant amounts of snow on the roof. That typically amounts to a few weeks in the spring. In snow-belt country, the real problems are when you get a lot of snow, and then a prolonged cold snap. Dams that build under those conditions tend to be huge and not to go away. And the heat that is causing them is not coming from nature, as the lack of dams on the barns and empty houses under the same conditions attest to.Steve
*If you think about it, its not that rare at all. After 3 pm or so it gets colder so the melting stops and the freezing begins. My feeling here on this thread was that he did not have a major ice dam. If his inside and out side temp are within 1 degree, I would have to say he is right on the money. I have noticed over the years the 4 and 5 pitch roof systems seem to ice dam even when conditions of attic are right on the money. Though rarley large .
*Ron,I've got to say here in central New York, it is pretty rare. We've got a lot of empty houses in my neck of the woods (pretty economically depressed here) and they have snow on them all winter. They almost never develop ice dams when heated houses right next to them do. Again, when the empty buildings do develp ice, it's in the late spring when daytime temps are warm enough to start the roof melting. Even then they really only develop small icicles, not ice dams per se.Maybe it's different in your climate.Where are you?Steve
*Right down the block in Milford PA. That is about 45 min. from Middletown NY. Yes, it is during this time of the year as you said that I have seen the ice damming and never a major thing. Upon further inspection of the original post , I noticed he said rather large.OOOPPPS.
*There are a couple of really good articles in fhb on roofs for snow country, and another on building a cold roof. Now, since you are already IN your "new" house I guess you don't want to be doing a lot of this kind of rebuilding...Ice damming occurs for one reason: The roof over the house is warm, so it melts the snow, and when it runs to the eaves it hits the overhang, which is not warm and then the stuff freezes. What pitch is your roof, and what is the roofing material? I'll assume shingles all the way. Since shingles are high-friction, they're more prone to ice damming. Some houses here in Fernie, BC that have shingles have them all the way to the wall of the house, then the overhangs are tin. This seems to help, but not entirely. If you have a mellow pitch on your roof, and the snow doesn't slide, ice damming is almost a chronic problem if you don't have a cold roof. Chances are your attic isn't as cold as your eaves, despite the measurement. I can't readily think how this occurs given your measurement except to hypothesize that when the temperature drops, it drops faster outside than inside. This would seem to make sense; the eaves are cooled faster than the attic, causing ice damming. You want to try to cause your roof and your eaves to cool evenly, to reduce ice damming. Here's a couple of suggestions:1. Run raftermates (there is a cheaper alternative in I think blue or black foam) all the way from the wall to the ridge. This is relatively easy, an afternoon with a hammer tacker should do the trick. I assume you have a ridge vent open to the attic. 2. If you don't have a ridge vent open to the attic, and have only gable-end vents, then you need to make your attic colder. You could run the raftermates to, say, a foot from the ridge, so your gable vent could suck air out. Possibly install a whirlybird. But, all other things being equal, if your roof pitch is mellow, and it hits, say, 36 degrees in the daytime, the roof will melt snow. The water will start running down. Then in the afternoon, when it cools off, the water from the ridge will run down the roof and if it doesn't get all the way off the roof by the time the roof hits 31 degrees, it'll freeze. My house doesn't have a big ice damming problem (few icicles from time to time) because the roof is steel with a 9-in-12 pitch. I have avalanches instead (you oughta hear it, every so often in a snowstorm I get this WHOOMPH!! sound). Other than heated eaves (which is a ridiculous, environmentally unfriendly idea) there isn't much more you can do other than the above suggestions. Check out the fhb articles if you can dig them up, they're very, very informative!
*One more thing: you said "north side". Hmmmmm. I don't have any ice damming problems on the north side of my house, and this may have something to do with the steep pitch of the roof: the north side of my house does not get sun on the roof till about the end of April, really. You may be having trouble because the sun is peeking over the ridge or warming up most of the roof, but not the eaves. Take the temperature of the roof skin, it may be much warmer than the attic itself!
*This is not permanent solution, but try this...it actually works. Take some old pantyhouse, cut one leg off, stuff it with some rock salt and tie off the end. Place it in the eavestrough before your annual ice dam builds up. Keeps the eaves trough clear of ice, and doesn't give the water a chance to freeze and build into an ice dam. Might be hard on the eaves trough, but it's easier to replace than your roof or your drywall inside.
*marko - your advice fixes symptoms. I say address the problems - like air leakage out of the house.Jefe - I really am stunned to hear that type of advice. How does the rock salt help with the condensation on the underside of the roof? Or the cost to heat and humidify the air before it leaks out and rots the roof? How much will this reduce cold air infiltration that results from the hot air exxfiltration. Again fixing symptoms and not problems.-Rob
*Rock salt is not good for your roof.
wow there's also looting it's a horror of some kind
we don't have this, we didn't have much of a winter
I hope you'll find it useful again
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Hi All,
This is the 4th season in my new old house and the last 3 have been quite mild for Maine. Very little snow to speak of. Well, this year snow has picked up.
The other day I noticed a very large ice dam on the north side running the whole length of the eave.
Its a bungalow style home , single story, unfinished attic. The only access is a hatch through a closet. The eaves have an overhang of about a foot to foot and 1/2 .
The attic floor has blown in cellulose between joists. Nothing in roof rafters. They are open to the roof boards.
I have never experienced ice dams before so I'm not sure what needs to be done to correct/eliminate the problem.
I plan to add some living space in the attic sometime in the future if that has any bearing of alternatives.
Any information would be greating appreciated!