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Old 12-31-2012, 05:55 PM   #1
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Ice dam roof leaks


I live in Wisconsin and we received around 16 inches of snow a couple weeks ago, and it hasn't been above freezing since. Our house is 1.5 stories, and the finished attic is poorly insulated. To try to prevent ice dams, I raked the bottom 3-4ft of most of the roof, and as much as I could (all but the top 3ft) of a known problem area.

This didn't work. All it did was move the ice dams up higher, and on the north side of the house, the 3-4ft I cleared turned into an inch thick layer of ice, with a dam several inches thick at the top of it. Over the last week, we've been having several spot leaks that thankfully I've been able to get to, but I wanted to finally put an end to it and paid someone to steam all the ice and snow off our roof.

During that process, I noticed a few spots of water on the floorboards in the unfinished parts of the attic (inside the kneewalls) while they were steaming/spraying the roof.

Could this be indicative of a leaky roof, or perhaps it's just ice that was already under the shingles finally being melted, and had to happen sometime? The asphalt roof is ~5 years old, and the shingles look in good condition. I have not noticed water in the attic in previous rain storms/etc., but I do not check every time it rains.

I will be attempting to airseal and reinsulate the attic as best I can soon, and don't want all my work to get soaked and ripped apart in the future.

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Old 12-31-2012, 06:08 PM   #2
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Ice dam roof leaks


It sounds like you know how to correct the problem which is good. The ice may have already been pushed up the shingles and now melted.

Increase your insulation and make sure to have the proper ventilation.

You could always try to install some gutter cables to help keep that area melted.

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Old 12-31-2012, 06:27 PM   #3
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Ice dam roof leaks


Quote:
Originally Posted by ParagonEx View Post
It sounds like you know how to correct the problem which is good. The ice may have already been pushed up the shingles and now melted.

Increase your insulation and make sure to have the proper ventilation.

You could always try to install some gutter cables to help keep that area melted.
+1

Be sure to air seal as well as you noted. Additional insulation is part of the equation a leaky envelope will still melt that snow.

Ventilation will help remove the radiant and air loss heat.

Best bet is the combination of all of the above mentioned (air seal, insulation, and ventilation).
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Old 12-31-2012, 07:06 PM   #4
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Ice dam roof leaks


The melt water is going under the ice layer and backing up under the shingles. The only way you can be positive this doesn't happen again is to run a heat trace cable from the roof ridge down to the gutter and continue the full length of the nearest down spout down to mother earth. Any ice that forms there can be safely dealt with. Why does that work? A dam with a hole in it won't hold water.
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Old 12-31-2012, 07:16 PM   #5
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Ice dam roof leaks


In your zone there should have been Storm and Ice shield installed under the shingles at least at least 4' up from the bottom edge of the roof so this did not happen.
Even in VA it's code. I'm sure in your are it's even more so.
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Old 12-31-2012, 07:20 PM   #6
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Originally Posted by joecaption
In your zone there should have been Storm and Ice shield installed under the shingles at least at least 4' up from the bottom edge of the roof so this did not happen.
Even in VA it's code. I'm sure in your are it's even more so.
Actually IW isnt code here yet in WI unless its under a 4 pitch. Then it's only two feet inside the warm wall so either one or two courses.
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Old 12-31-2012, 07:33 PM   #7
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Ice dam roof leaks


If that's true (and I have no doubt it is) then someone skiped that part or there's poor insulation and or venting.
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Old 12-31-2012, 07:58 PM   #8
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Yeah I think it's pretty crazy too.
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Old 12-31-2012, 10:05 PM   #9
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Ice dam roof leaks


There is not very much insulation (loose fill fiberglass in various states barely half-way up the 2x6 joists of the unfinished part, with R-11 fiberglass batts in the knee walls and presumably the finished ceiling), and ventilation isn't great either. I wouldn't be surprised if IW was skipped when it was last roofed.

I'm considering taking out the old loose-fill since it's nasty, possibly the batts as well since they're not in great shape. Then I might put cotton (e.g. UltraTouch) batts in the knee walls and blow in cellulose above the finished ceiling and in the unfinished floor. I'll also be putting in ventilation channels at the soffits and between the kneewalls and finished ceiling. Above the finished ceiling might be difficult, since it's inaccessible other than through the rafter bays if we don't cut into the finished ceiling, which I don't want to do, but might have to. There's also a shed dormer with a low-slope rubber roof that I don't know how to rectify relatively non-destructively.

Sigh. Not a fan of homeownership so far.

Thanks for the tips so far.
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Old 01-01-2013, 06:25 PM   #10
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Ice dam roof leaks


Truth is, if your home is suseptible to ice damming, any amount if insulation or IW won't help. ALL homes lose theire heat. It's the first rule of thermal conductivity. If you use more insulation, it will only slow the heat progression down, you can't stop it. If the design of your home allows for ice daming, you'll need to keep the melting snow from the escaping heat flowing to the ground.

The ice dams are formed under the snow where it has a nice cold place to freeze up after running down the roof to where it's cold. You can use a Self Regulating cable in serpentine runs up and down the roof (and in any gutters/leaders) but even they can bridge over in the weather you received.

The best choice is Zmesh under the shingles in the effected area. It will prevent any snow or ice from building at all. You can search for the name on the net as I'm not a proponant of selling on forums. Granted, you won't be able to do anything until spring so keep the rake out and look into the Zmesh system.
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Old 01-01-2013, 10:07 PM   #11
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Ice dam roof leaks


The following is a previous reply I made some time ago. You have to understand ice damming it to beat it. The term "Air Seal" is thrown around here a lot, and I think they mean well, but read this, it should help:

The key to avoiding ice damming is to keep heat from within the structure from escaping and melting the snow by warming the underside of the roof deck up from the eaves. Ice damming is much more prevalent in truss construction where a severe pinch condition exists at the eaves due to using 2x4 dimensional lumber. It is also exacerbated by minimal slope like 4/12 due to poor chimney effect.

Trusses made of 2 x4's restrict airflow through the soffit and up to the ridge. You want to maintain the temperature on the underside of your roof deck as close as possible to the exterior temperature. This prevents premature melt water from running down to the eaves which are usually colder due to their being extended out past the exterior wall. (Bridge Freezes before roadway?)

Back when everything was stick framed, Ice damming was usually not an issue, because we used at least 2 x 6 framing lumber for rafters, and cut a small bird mouth at the top plates. There was plenty of air flow under the deck.

If you use trusses at 4/12 you had better be installing SBS peel and stick Ice dams material at the eaves, to at least 2 feet inside the interior wall line. I spec 3 feet.

By the way, the purpose of melt wires is to melt a tunnel through the snow and ice for melt water to flow off the roof, not to actually melt the snow. That is why they run up and down in a zig zag, not parallel with the eaves.


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Old 01-01-2013, 10:12 PM   #12
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Ice dam roof leaks


It's 1953 construction and the rafters are 2x6s, so still not a lot of room, but better than 2x4s. The tricky part, I think, will be getting enough insulation/air-sealing in the peak of the roof, above the finished ceiling. I'm worried that we won't and then snow will still melt up there but then freeze above the unfinished portions.

For ventilation, there are two of those mushroom style vents on the south side of the roof (no ridge vent).
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Old 01-02-2013, 10:27 AM   #13
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Ice dam roof leaks


Can you please tell us exactly how your attic was finished? Is this a Cape Cod wherein they installed kneewalls about a third way up the rafters, and collar beams near the ridge? Do you have insulation stuffed right up against the back of the roof deck between the knee wall and the collar beams?

It would really be nice if you explained your situation better, or sent in some pictures of you upstairs so we could help you better.

It sounds like whoever designed your finished upper room did not understand what they were doing?

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Last edited by jagans; 01-02-2013 at 10:39 AM.
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