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Ice damming

Post in 'DIY and General non-hearth advice' started by cmonSTART, Dec 24, 2007.

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  1. cmonSTART

    cmonSTART Minister of Fire

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    Anyone else have an issue with ice damming on their roof. I had to knock a couple off this week because they caused some leaking. Is there any way to prevent it?

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  2. 11 Bravo

    11 Bravo New Member

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    Yep.....Pushed up shingles and water leaked in the first year I lived here....some suggestions that I have used.

    1) Use long handled snow rake to pull down the snow from the first couple feet from edge of roof allowing drainage

    2) "Roof Melt" brand salt blocks. Comes in a bucket, each are the size of a hockey puck...I toss them up a couple feet in from edge.

    3) Use a long thin sock or hosiery. Fill it full of potassium cloride pellets, (comes in a bag for water softeners). Tie a knot in the end, and lay it perpendicular to edge of the roof to melt a drain valley. I was told to do this instead of regular salt, which supposedly can damage shingles.

    4) I do not use this but lots of folks use the heat tape on the roof which plugs in and warms up to melt ice.

    Plenty of folks on this site have done roofing, they might have better suggestions, but that is what has worked for me and I haven't had any problems the last 4 winters.....

    Merry Christmas
  3. Ridgefire

    Ridgefire New Member

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    When I re roofed I used the Ice and water shield under the shingles, its basically a rubber membrane so if ice does get under the shingles it doesn't get into the house.
  4. stop drop & roll

    stop drop & roll New Member

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    Few years back, saw a neighbor using a roof rake after a heavy snow storm. I thought it might be a good idea. I went out and bought one and shoveled about 6 feet off the edge of my 3 year old roof. Worst mistake of my 10 year home ownership to date. The edge of the snow that wasnt removed froze, and the next day melted, wicked up under the shingles after the ice and water barrier and rained in behind my walls. Thank god for homeowners insurance. I would think twice about that method. For now on, I just leave it alone. Good luck!
  5. jklingel

    jklingel Feeling the Heat

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    START: That is an ominous sign sometimes. I'm sure curious as to WHY you have ice on your roof. Is it because of excessive heat loss, or insulation too close to the roofing material? A little ice is normal if you have that drip-in-the-day, freeze-at-night weather, but it sounds like you have a lot. Any idea why?
  6. PAJerry

    PAJerry Member

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    I went through that problem last winter. Had leaks in 3 rooms and spent a lot of time chopping the ice off the roof. We finally bit the bullet and put on a metal shingle roof and the snow comes sliding off after accumulating 3 or 4 inches. Nicest sound in the world after last year. One other thing I did was insulate the top and sides of the insert, and the masonry does not get anywhere near as warm as it did last year, preventing heat from going to the attic area and causing snow melt on the roof. Insulating your chimney might also help.
  7. stop drop & roll

    stop drop & roll New Member

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    Check out familyhandyman.com and search ice dams. Alot of past articles on ice dams and attic ventilation.
  8. jklingel

    jklingel Feeling the Heat

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    Sliding snow gives me the creeps. Several years ago, we had about 3' stacked up on our roofs, so the town was all out shoveling roofs. I was finishing my garage (aluminum) roof, and had a strip about 6' wide by 18' long awaiting me and my shovel. I was on the ground, moving a ladder so that I could climb up in the snow and shovel, as the bare roof is too slippery to climb. Suddenly I heard a "crack", and started running before I even looked up. Unfortunately, running in bunny boots and Carharts is not fast running, and a wug of snow 6' x 12' poured off the roof and encased me up over my waist. Believe the guys who say that after an avalanche the snow is packed like cement. I was locked in solid, barely able to wiggle my toes. After hollering for help for a bit (house is 75' away, 13" walls. No one heard) I realized that if I were going to get out before the remaining 6' came down, it was up to me. I dug by hand enough to get my feet out of my boots, and wiggled free, sweating like a pig by then. I am very thankful that somebody held that last 6' up there; that could have been ugly. The moral of the story? I put avalanche anchors on the roof and shovel it now, not having to worry (so much) about slides.
  9. dlpz

    dlpz New Member

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    I've had a pretty good (bad) issue with ice dams. Heat cable and all that other stuff are only band aids for the problem. The solution is properly insulating and sealing you attic from below and properly venting your eaves. Use Rafter mates to ensure that your insulation doesn't block the soffits. Also make sure your insulation isn't touching the decking of the roof as this wicks heat. If it comes down to getting a new roof, strip it and put ice barrier up 9 ft. from the edge. Depending on where you live and what your roof pitch is, just like you clear your driveway, unfortunately you have to clear your roof as well.
  10. cmonSTART

    cmonSTART Minister of Fire

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    Heh, ya, I do have a lot. We live in a 157 year old farm house, which isn't anything I would call insulated. It has a little here and there, but it loses a bunch of heat. In fact, so much through the one part of the roof that from the outside, I can see where the old log trusses are for the roof because the snow remains there in lines above the trusses.

    Anyway, I guess I know WHY I have these ice dams (cause I have an old house which needs insulation and a new roof), I was hoping for a good temporary solution to get us through to when we put a new roof on (hopefully this summer!!!). I like the salt idea. I thought of that but wanted to check before I started tossing potentially corrosive stuff up onto my already sickly roof.
  11. Hogwildz

    Hogwildz Minister of Fire

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    The normal remedy for this problem is ice & water shield on the last 3' of roof at the eaves, also in the valleys and around skylights etc. The worst problem is at the eaves (gutter edge). Ice & water shield will stop this problem. You could also try the heater line that runs zig zag along the last few foot of roof at the eaves, and also runs in the gutters & down the spouts. My ol man had been using it for years and works well.

    It does not take a large amount of ice for dams to develope and back under the shingles and run in the house. Especially with less steep roofs.
    After a few days of thaw and refreeze it can happen.
  12. richg

    richg Minister of Fire

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    Gang,

    I have become quite the expert at ice dams over the past few years. They are a sign of serious trouble in your attic, but they also represent an opportunity for big money savings. You have some work to do:.

    -Ice dams are caused by warm air leaking from the living space into the attic. The warm air melts snow on the roof, which then freezes when it hits the unheated eaves. Water continues to melt, and backs up behind successive layers until it works its way under your shingles and into your house.

    -Ice & water shields are an absolute must. A popular version is GAF's Weather watch. However, ice & water shield is like the spare tire in your car, meaning it should not come in to play if your roofing system is working well. It is a last line of defense.

    -You have a serious air infiltration problem into your attic. That's the bad news. The good news is that once you fix it, you will see large savings in your heating and cooling bills.

    -To fix the problem, go to Home Depot and buy the Great Stuff Pro 13 Foam Gun, and about ten cans of Foam. Don't bother with the "all in one" cans. Gun foam is the way to go for this issue.

    -Go up into your attic and start pulling back insulation and look for areas where pink insulation has turned dark, which indicates that dust-laden air has been moving through the insulation. Common penetrations include vent pipes, chimneys, light fixtures, electrical wires, and the biggest one of all, interior wall partitions. Insulation will retard heat loss, but it will not stop air movement. Yes, most insulation has a vapor barrier on it, but unless the insulation was laid with the precision of a neursurgeon, air WILL find a way to get out. Fill the gaps with the foam, taking care to seal it completely.

    -Next, check where the roof meets the outside walls. You will likely see penetrations there as well.

    -Check your sheathing for mold growth. This is very common in air-leak situations, and must be rectified on a priority basis or your sheathing will get trashed. While the internet is rife with claims of, "BLEACH DOES NOT KILL MOLD", I have found that bleach will knock it out in a heartbeat.

    -Reinstall your insulation, making sure that the vapor barrier is continuous and that no air no where no how can get into the attic. If needed, build or buy an attic hatch insulating cover.

    How do I know all of this? Well, I been there, done that. Here is a picture of a massive air infiltration into my attic, and please take note of the massive blackening of the insulation. The Great Stuff you see as shot from below by me four years ago during a bathroom renovation. My attic had penetrations bigger than the Grand Canyon. I have sealed about 90% of the leaks, and my house is now warmer with the P61 set at 65 degrees than before, when I had it set to 70. Yes, you have a big, pain in the butt project ahead, but the results will be more than worth it.

    Attached Files:

  13. velvetfoot

    velvetfoot Minister of Fire

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    richg,
    Can I ask how old your house is?
  14. richg

    richg Minister of Fire

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  15. Hogwildz

    Hogwildz Minister of Fire

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    Richg is absolutely correct. But all ice damning is not necessarily due to heat loss &/or air infiltration in attic. I agree with him, check for air leaks, gaps etc. Fix these if you find them, but most ice damning occurs merely from the days sun melting the snow/ice on top of the roof surface running down and refreezing as the day goes on and starts getting colder again toward evening. This is where the ice & water shield comes in play. So yes eliminate heat loss problems in the ceiling under the attic, The attic itself is made to vent, ridge vent, vented soffit, gable vents etc. You want air flow in the attic cavity, but not from the heated interior of the house.
    Again, as Richg said, eliminate heat loss from living space below attic, but you may also need to get ice & water under the eave edges to combat normal roof surface melt/freeze caused ice damns. Not to down play heat loss into an attic, as it is a major energy waster. But in a vented attic, the nominal heat loss into a cold vented attic is not the majority for causing ice dams on the roof surface. It would take almost a furnace blowing directly into the attic to heat the air & underside of th decking enough to cause this type of problem. And in a vented attic, usually what nominal amount of warm air that does leak into the attic is diluted and cooled much too fast to warm anything up there or make much of a temp change. Now if the attic is not vented properly & is tight, dead air, then you could have a problem with temperatures raising some in the attic space. No attic/roof system should be air tight, if it is, you will find the underside of the decking black, moldy or even rotting from the underside duw to moisture & heat build up in warmer/hotter months and no air circulating in the space. I have seen this countless times, especially with cathedral ceilings, where the insulation was laid to fill all the way up to the bottom of the plywood or whichever decking they used. No air flow= rot, mold, and premature aging of the decking. And also prematurely shortens the shingle lifespan.

    Most damning occurs down near the gutter edge, valleys & curbs. Most residential structures do not have curbs, but most have gutter edges & quite a few have valleys.
    At the gutter edge the days runoff refreezes in the gutter, building up ice to above the top and as the runoff comes down it now starts hitting this damn and running running back behind the gutter and then sooner or later up under the shingles. Another reason for vented soffit, especially extended soffit, is if the damning does occur at the gutter and runs back in, it at least runs down onto the vented soffit and drains back out before getting back into the wall. Unless the soffit is pitched towards the wall. Not saying you would want this to happen, but better this then finding the wall and running into the wall.
    Same can happen in the field of the roof, run off freezes, creates a damn, next run off comes down, hits damn refreezes back until it gets under the shingles, until it backs up enough to hit a seam underneath, and sooner or later the runoff finds the seam and leakage occurs. Usually in the field this is due to a low spot in the decking, a slight bow is sometimes all it takes. But the majority of ice dams & leaking caused by them are at the eave (gutter) edges, and withing the first couple feet. This is why ice & water shield is spec'd on almost every home built these days. Ice & water is a roll of sticky asphalt self sticking underlayment made specifically for this purpose, hence the name. When the shingles are nailed down, the nails do penetrate the ice & water shield, but the asphalt of the material seals around the nails. So if installed correctly, which a lot of places do not do, even though damning may happen, it typically does not back up over 3' and will harmlessly run back down when it melts. Ice and water shield should be run the full length of the eave, and the edge should come down and onto the fascia or face board an inch or so. So when the gutter is installed, the ice & water shield is below the rear gutter top edge an inch or so and sandwiched between the gutter & face board. Now if the gutter damns up and water runs back it has no where to go but down between the gutter and ice & water shield once it melts. If you just run it to the edge of the decking, it can still run in at the seam of the decking & fascia board. Keep in mind alot of ice & water shield products are not made to withstand direct sunlight for any long period of time. So just sticking it on and not covering with something will enable it to deteriorate in time. There may be newer products that are resistant to this, but in most cases, the ice & water shield should not be showing or exposed in the first place if done correctly.

    Bottom line, seal air leaks & install ice & water shield, and be done with it. Or in time things will rot and even more work will have to be done.
  16. d.n.f.

    d.n.f. New Member

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    There is some aluminum/steel (I saw it on Holmes on Homes a Cdn tv show) that replaces the last row or two of shingles. So the last one or two feet of roof is now slidy steel and only that part sheds off. Plus you add in an aluminum gutter guard and nothing sticks in your gutters.

    Steel roof are fine until they kill someone. We just had a guy die out in Nelson BC area two weeks ago. Shovelling his driveway and the roof let go and was killed by the snow. Don't walk under the drop zones in avy conditions.
  17. focusontheworld

    focusontheworld New Member

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    When you say these days, how long has this been common? Would 2001 qualify? In Colorado?

    BTW, thanks for a very useful explanation. Dead on for me.

    Tom
  18. JustWood

    JustWood Minister of Fire

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    My 4 year old shingles leaked, next summer off they came and on went metal. NO more problems. Had to spray insulate the roof because of sweating issues.
  19. Hogwildz

    Hogwildz Minister of Fire

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    In PA. yes, not sure for CO.
    But it is a pretty standard practice since I'd say early to mid 90's.
  20. focusontheworld

    focusontheworld New Member

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    I bought a new spec home in Aspen, CO that was built in the 2001-2002 timeframe. It's a high end home that cost about $3million to build. Heat tapes were installed during construction all around . The roof started leaking last year and now this year due to ice dams and 30 foot icicles. I'm being told that it is common practice to shovel the snow off the roof in this area to prevent ice dams. The cost and safety of shovelling snow off a 5,550 square foot 2 1/2 story building is one thing. The problem I have is that I would not expect that a home at this price point built as recently as this one would leak whether we shovelled the snow off the roof or not. I would have thought that roofing technology would have come along by the year 2001 to prevent the leaking, if the technology was used. I'm doing my homework now before approaching the contractor as I am in my last year of construction warranty and want to get this fixed as part of the warranty, if that is fair. FWIW, all the top floor rooms have catherdral ceilings so there are no attics. The roof is 75% shake but metal over some roof section for decorative reasons only - different roofing materials for variety. I haven't yet investigated to see if their is a ice membrane underlayment.

    Does shovelling the roof every winter in this scenario seem normal?
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