Preventing Ice Dams for good

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Old 12-07-19, 04:29 PM
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Preventing Ice Dams for good

Okay, my house is 42 years old, new roof in the last five years, new attic insulation within the past five years as well. We had ice dams in the past but only small ones since the new insulation. We also have ice and water shield six feet up from the roof edge. Even with the ice and water shield we had a leak in the bad winter of 2015 in NH. Huge ice dams which it seemed every one had. The last few years have been okay but theyíve been easy winters. Well we had our first snowfall about a week ago and it dropped about a foot of snow. Sure enough a week later and I have small ice dams. I even noticed some brown streaks down the siding in one spot already. I thought ice and water shield would prevent water infiltration? No leaks inside yet. Short of removing snow from my roof each storm, Iím at a loss for what to do and am ready to sell the house. What else can I do? Metal roof? Tear up a five year old roof and add ice and water shield over the entire roof? Canít do that now since itís winter. Even with new blown in cellulose insulation I still see snow melt on my roof. Very frustrated and discouraged at this point. Love the house except for this one thing. Other houses in the neighborhood look similar as mine relative to the ice build up. Any help or advice would be appreciated. Thank you.
 
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Old 12-07-19, 06:07 PM
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Well, sad to say someone probably dropped the ball on your roof. If your roof is low slope (2:12 to 4:12) the felt paper should have been double lapped. They probably lapped it a couple inches which is not enough to prevent leaking during an ice dam.

We assume that they insulated the top plate (between the top plate and baffles) and that you have adequate air intake at the soffits washing cool air under the roof deck.

You can help melting by running heat cables in the gutters and downspout, and zig-zagged on the roof over the soffit and top plate area (where the roof-ceiling proximity is the closest). Keeping this area ice free will usually help the areas above.

Snow rakes can help. But you don't want to scrape up the new roof either.

There could be other issues but no way for us to comment on every issue sight unseen. A house inspector might be able to give you more ideas.

Yes a metal roof would be better than an asphalt one. But only you can decide if it's worth it.
 
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Old 12-08-19, 07:27 AM
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Hi Matt, living in Maine I'm well aware of ice dams and some of the steps to eliminate most of them. I say most as some are caused by the sun at selected temperatures and snow cover, but address all of the rest and those will be minor.

To start we need more information as X said like slope of the roof. A picture would also details like valleys.

Attic ventilation both high and low should help keep that attic cold avoiding the melting stage. But no mention about air sealing that ceiling which should have been done before the cellulose. And air sealing involves a lot. let us know if and air sealing has been done.

Proper ventilation and air sealing and that roof will perform like a brand new house.

Bud
 
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Old 12-08-19, 10:29 AM
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Yes the attic floor was air sealed prior to the insulation. Honestly the ice dams have been minimized since then. Still Iím paranoid when I see any accumulation of ice at the edges. I think I need better air flow especially at the soffits as there is none right now. Thing is though, when thereís frost Iíd say about 95% of the roof is covered in frost. As such doesnít that mean my roof is cold? My roof is currently snow covered right now but obviously snow is melting. Iím just confused and tired of having to deal with this.
 
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Old 12-08-19, 10:53 AM
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It's the bottom ľ" of snow that melts and runs down to where it is exposed to the cold air. The layer of snow insulated that water and prevents it from freezing. Ice dams have a range of temperature where they form. Too cold and no melt. Too warm and no freeze. In my area it is around 10į to 20į when icicles will form.

You say no airflow at the soffits, can you explain. Is there no soffit vents? There are guidelines for the amount of NFA (net free area) for upper and lower ventilation.

What climate region are you in?

Just want to add one example. If you were to rip everything off of the roof down to the sheathing, install all Ice and water shield, and all new shingles, guess what? Nothing would have changed in terms of forming ice dams. All of that work would have been to keep the snow melt from coming through, but the temperatures that form the ice dams would remain. lets get the ventilation working.

Bud
 
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Old 12-08-19, 12:21 PM
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Do you have roof vents?
Do you have gable vents?
My place was built with just gable vents but the first time I replaced the roof I had roof vents added.
I never had problems but it seemed like a good idea to do it while it was convenient.

Soffit venting should help.
I added vented aluminum soffits when I redid the fascia, again it was a convenient time to do it.
Had a few soffit vents but felt more is better,
If you have plywood soffits and your facia hangs down an inch or more then adding vented soffits is not that difficult.
Just attach a jmold to the underside of the plywood soffit. I would use screws as soffits are usually thin and banging on them is not a good idea.
Then cut lots of holes in the soffit and slide in your aluminum vented soffits.
This may or may not be possible depending on your roof but is just an idea.
 
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Old 12-08-19, 02:02 PM
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I have a ridge vent and gable end vents. Soffits are not open meaning theyíre just plywood. How do I get a pic in here?
 
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Old 12-08-19, 02:27 PM
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Putting pictures in your post.

Not every house is built as modern houses are, so not every house can have the ideal soffit ventilation that is common nowadays.
 
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Old 12-08-19, 05:31 PM
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When I worked for a landscaper/arborist, our winter work would be firewood and snow plowing: we had one customer with a nice old house, slate roof, and ice dam problems.
Our snow clearing kit included a "snow rake" (actually a commercial 3-foot wide push broom and four swimming pool extension poles) AND several bags of the peanut sized water softener pellets. Push/pull the snow off with the broom, but leave a little snow. Then hand toss a few bags of water softener pellets up onto the roof. The ice dam generally broke loose within an hour or so.

Later, we had an office (former 7-11 building) where the front roof segments pitched down to a 12x12 tar roof "porch". Which of course always froze. Best solution I found was a cinderblock, a 5 gallon bucket, and a 40 lbs saltlick-block. Set the concrete block in the corner, flat sides facing up/down. Place 40 lbs salt block on cinder block. Un-clip one handle from the 5 gallon bucket, place bucket OVER salt lick while sliding handle through the center hold of the cinder block. Click the handle back into place. You now have an automatic snow/ice dam salt de-icer. The bucket keeps the salt from washing away. When the snow/ice build up rises to the height of the cinder block, it contacts the salt, forms brine, and dissolves the ice/snow until it drops down below the level of the concrete block.

I've only had an ice dam problem once or twice in our old farmhouse, Halloween blizzard a few years ago. I found it was easiest to just open the door to the attic, let the hot air rise up to the attic. After about 90 minutes, the ice /snowpack slid off and that took care of it.
 

Last edited by Hal_S; 12-08-19 at 06:14 PM.
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Old 12-08-19, 08:40 PM
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How does snow get under the upside down bucket in order to build up (eight inches) to the level of the salt lick block sitting atop the concrete cinder block?
 
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Old 12-09-19, 06:34 AM
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How does snow get under the upside down bucket in order to build up (eight inches) to the level of the salt lick block sitting atop the concrete cinder block?
Good question, actually, that's part of the elegance of the solution.
It's really more about ice/water than snow.

SNOW doesn't rise to the level of the salt; snow simply slides down through the holes of the concrete block, meltwater goes through it, or around it.

But, if there is a buildup of ice and water, those DO get under the bucket and up to the salt block.
 
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Last edited by Hal_S; 12-09-19 at 07:36 AM.
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