Do Ice damns always mean damage?

[Worksmart]

Stanley - I would say no from personal experience. My Cape Cod roof is a steep 8 or 10 on 12 pitch. I got some nasty dams shortly after I moved in in '97. Never got any interior damage, luckily. I am now a raking fanatic too. Chuck

[RobS]

Our roof is quite steep at 14:12. I was surprised to see the ice dam but again, I'm not too worried about it. For there to be damage melt water will have to travel up under the shingles. That's where the steep pitch should really help.

Most places the snow isn't even staying on our roof. This particular spot is where two roofs intersect forming a valley. It's collected more snow there than anywhere else [img]/forums/images/icons/smile.gif[/img]

[Boondox]

A neighbor got great results by sealing his attic with those foil-covered foam sheets from one end to the other, and using spray foam in the corners to seal the house heat out. His attic is much colder now. Sounds a bit like what you were describing.

Pete

[beenthere]

If I understand you right this sounds like your neighbor put a vapor barrier (foil-covered foam sheets) on the cold side of the attic insulation. This will make for some very wet, and ineffective insulation under the foam sheets if that is the case.

Maybe I missed the true picture.

There is also a product that you put on the roof like tar paper. I can't remember the exact name of it. But if you put this on you never have to worry about ice damming and the resultant water down the walls.

We had this problem at my office building. Had to tear up the shingles 4 foot up all the way around and put that material down. Since then we have never had a problem.

[hazmat]

The weatherman says 40 deg & raining on sat. I'll Probably know then if we've got any damage.

[Stoneheartfarm]

Rob,

Yes, sunlight and general weather can do it too. If it warms above freezing during the day and then drops to below freezing at night, you stand the chance of starting an ice dam, no matter how well ventilated or insulated you are.

There are basically 2 cures that I have seen for this situation. One, Cowboydoc has already mentioned, and this is to use an ice and water dam type product. The other is to use 2-3 feet of sheet aluminum between the bottom shingle and the end of the eave.

When I roofed the cabin. I ran with the sheet aluminum 3' wide. On the house, we went to ice and water dam laid under conventional shingles. Neither has leaked. The house has very little heat leakage and so we haven't had much real ice. The cabin on the other hand had a lot of it. (Both heat leakage and ice). The only problem with the aluminum is that ice dams will tend to come off in a solid lump, and can destroy (or kill) anything they hit. (mini icebergs). This is also why I have been cautious of metal roofs on buildings, although no one I've talked to has had any problems.

Steve

[Argee]

Ice dams are usually caused by inadequate insulation where the eave wall meets the rafter or truss. There is too little room there to stack enough insulation over the plates of the wall. Or (As Steve pointed out) there is so much insulation crammed in to that little space that it blocks the air flow from the eave vents. A roof has to breathe, if it doesn't you also stand the chance of your sheathing rotting out. The heat from the house escapes at that point warms the underside of the sheathing and melts the snow on the roof above. When the temperature dips at night it freezes. Over many days and nights of this action it creates a dam thus allowing water to back up under the shingles. Sometimes, due to the poor design of the roof or trusses it is unavoidable. In those cases I would install ice and water shield up the entire roof. If I were building a new house I would install trusses with energy heels to allow for additional insulation. I have energy heels on my trusses which allowed me to install over a foot of insulation directly over the wall plate. The snow that goes on the roof at the first snowfall of winter is still there in the spring without forming any ice. I also installed ice and water shield over the entire roof for peace of mind.

[Worksmart]

Cowboydoc - "Ice and water shield" is the common name used in my parts.

Standard practice is 3' along lower edge of roof. When I had my house re-roofed 2 years ago, my roofer has now gone to 6' wide coverage of ice and water shield.

Chuck

[Argee]

<font color="blue"> Standard practice is 3' along lower edge of roof. </font color>

Actually common practice and code for that matter is 3' from where the eave wall meets the roof. Dependent upon your overhang that could be 3' to 6'.