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Slate Roof Central Message Board » Ice and Water Membrane, Plywood, and other Controversies » Ice Dams, slate roof, and parapets in Chinook Country? « Previous Next »

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Anonymous
Posted on Saturday, December 24, 2005 - 03:24 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I'm a novice looking at building a house, with SIPS roof R40, ICF walls, want slate on top, but have castle-like parapets at base of entire roof perimeter, slopes 7/12 and steeper. Potential for snow drifts/ice dams at base of roof at parapets. Weather in Chinook country is cold two weeks, then Chinook comes in and snow melts, but potential for increasing ice in evenings. Good luck my finding a slater in these parts.

I understand increase overlap of slates in lower areas, ensure Rosin over any perimeter Ice/Watershield, extend metal flashing (i.e. copper)higher up under roof edge along perimeter(this metal should be over the Rosin, with the Rosin on top of the Ice/Watershied?), consider heat tape. Is it better to use 1/2" slate at lowermost part of roof (to reduce crmbling of the slate due to repetitive freeze-thaw cycles)
Any other recommendations to maintain longevity of the slate and to reduce impact of piling up snow and ice?
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Anonymous
Posted on Saturday, December 24, 2005 - 04:02 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

The parapets are boxed, from 9" to 33" in height leading up from the top of roof. I've heard Tri-Flex 30 would be a useful product over any Ice/Watershield instead of Rosin, or on top of it?
Should I be putting a more solid wood base on top of the OBS SIPS?
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admin
Posted on Saturday, December 24, 2005 - 10:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Everything seems wrong about this picture. Why are you putting so much emphasis on underlayment? It sounds like you're expecting the roof to leak and somehow think the underlayment is going to stop the water from coming in. It won't. The only way to do it right is to make sure the design will work and the metal and slate work is done correctly.

Half inch slates don't matter. Standard thickness will do.

The rosin paper is to allow the metal to expand and contract (i.e. move) after it's installed.

The underlayment is to keep the water out of the building until the finished roof is installed. After that, it's the slates and flashings that keep the water out, not the underlayment.

A dam at the bottom of the roof does not sound like a good idea. Parapets are usually limited to the gable ends.

Furthermore, an OSB deck is probably the lowest quality, shortest lived decking you can install.

Joe Jenkins

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