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On the Rain in Spokane thread, DJ in WA gave me some useful info about ice dams.
They have certainly overwhelmed my little cabin this year!
My cabin is an ancient mobile home, under a face lift of real, cabin style, metal roof, and T1-11 walls on exterior. Looking into the attic, between the cabin metal roof, and the top of the old mobile home, there's no insulation, save what may be under the metal of the old mobile home.
DJ in WA's premis is the need for insulation, and ventilation, between the old mobile and the cabin style metal roof. Good idea!
Now, the giant ice shelfs of ice dams seem to be causeing the melting ice water to run down the walls, both outside and inside of the house.

I'd sure appreciate all suggestions on how you folks have coped with similiar messes yourselves. SIL tried hammering to break up the ice burgs to get them up. With daylight, our assault on the ice dams will renew.

Come summer, do we need to remove the metal, and reinstall it with some sealant, or goo to prevent water from running under the metal?
Will deep insulation and improved ventelation prevent the ice dams from forming next winter?
All ideas appreciated.
 

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Ice dam forms when part of your roof gets warm - snow melts, runs down the roof, and hits a part of your roof that is _not_ warm. Refreezing. This happens over several days, and the ice builds up kinda deep. And solid.

Then when new water comes running down, it backs up behind the seams of the roof material - shingles, metal seam, etc. And runs down inside the building somewhere.

It is typically caused by poor insulation on the top of your house with heat leaking up through your roof.

When this extra heat melts the snow & it runs down, it hits the overhang part of your roof, where there is no warm house below it. This part of the roof is not heated of course, and where the ice builds up.

It can also be caused a bit by certain sun angles/ shadows.

The fix is to insulate the top of your building. Sounds like you have a real nice attic area to do that easily! Will save you a lot of heating costs, and get rid of the ice dam issues. You want the ceiling of your building to be well insulated; and you want the same cold air above & below the actual roof material - so yes ventilating that roof area will help too, but be sure to insulate to save heat inside your house.

Also, very important to use a vapor barrior on the proper (warm) side of any insulation. Or you end up with a real mess!

I don't know what your house has in the old roof, but if nothing, I'd lay down a vapor barrior, as much insulation as I could, and then open up some vents in the peak of the new roof to let cold air curculate above the new insulation, & cool down the underside of your roof to the same temp as the outside is.

Ice dam would be totally gone.

In many areas it is code to have to put down a real sticky tar paper type material along the edge of the house to cover that unheated overhange & a bit of the heated part - so if an ice dam does form, the water will back up through the shingle seams & still be sealed up ther on the roof because of this special sticky sealed barrior.

I'm not sure it would pay to redo your roof now with this - spend the money on the insulation if it is as easy to do as the picture of your situation is in my head.


--->Paul
 

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Until you are able to add the insultation and ventilation to the roof, you can remove the snow from the roof. No snow = no ice dams.

Get a roof rake or one of those Avalanche style roof rakes to remove the snow while standing on the ground. This should help out until the spring.
 

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Apparently part of this thread was lost due to reverting to a back up copy, so I will repost my earlier contribution in case you didn't see it.

I agree that ventilation in the "attic" is the key issue.

I am just completing renovations to a mobile with an "aftermarket" roof added on. Here are some additional things to check for:

1. Was your plumbing vent stack extended beyond the new roofline, or is it venting into the attic?

2. If you have a bathroom fan, is it vented into the attic?

3. Where is your clothes dryer vented?

Venting any of these into the attic would make your situation much worse. In the reno I am just finishing, the prior owner had extended the plumbing stack okay but vented the bathroom fan into the attic and the clothes dryer into the crawl space underneath.
 
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