Question for Slaters out there...

Hello gents, I have a client in Big Sky, MT that is interested in using slate on his new fishing cabin. I have installed and repaired slate in the mid-atlantic region of the US and love the material and style. That said, his property is at approximately 8,500 ft of elevation with roughly 350-400 inches of snowfall per year. Furthermore, the freeze/thaw cycles here are obscene and the roof has several shed dormers and shady pockets that will facilitate the growth of the enormous ice dams that dominate roofs here in Big Sky country throughout the winter months. The structure is well-insulated and has a cold roof, but don't be fooled. We clear snow and ice off of 80+ log mansions every winter here and the cold-roofs and sufficient insulation alone will not prevent severe ice damming in several key areas. We are a quality outfit and the details, flashings and dry-in will be to the nines, but my gut says the slate will have issues where the ice dams will form from expansion and contraction cycles, particularly at the junctions between the 10/12 main roof and the 5/12 shed dormers. Does anyone out there have experience with slate in this severe of an environ? I want to make sure that our clients maintenance costs will remain low enough to warrant utilizing a slate roof system. FTR - We plan on utilizing a radiant roof de-icing system under the 5/12 shed dormers (which will be standing seam) and can bring it up a few feet past the tranny. The radiant, however, will not last nearly as long as the roofing, so eventually this "solution" will have become a short term fix... Your thoughts, please. Best, Dave

We have lots of slate roofs but nothing like the weather you describe in fact we have so little snow snow guards are not regarded as important, we get plenty of rain though :)

My thinking is it doesn't matter how thick the slates are they are never meant to be walked on let alone hammered and chipped to remove ice.

If there is a plywood deck you have the opportunity to apply two lines of protection, my choice (although remember my location) would be to apply a breather membrane on the deck then follow wywoody's specification.

Just make sure you keep the top roof well vented.

wywoody Said: If you have the budget for it, you could go with a batten/counterbatten system. Not only would it give better drainage, it would create another cold roof system between the slate and plywood.

Now that's interesting. I never would expectt o see plywood under slate. It's typically put on wood decks, or wood slats. Any moisture that did make it through would dry up with no damage. Plywood, on the other hand would become a disaster.

Are you over thinking it? We only get 1' to 2' at times and I follow Berger's reccommendations to retain snow on the roof. As a rule, few if any of these houses have any felt, much less I&W shield and I never see leaks from damming. http://www.albertsroofing.com/SnowGuard%20Installation.htm Of course, many are older houses with less insulation and many are draftier too I suppose.

It could also be that holding the snow and ice stationary and preventing areas of buildup may be the cure in itself.

Thanks for the tips old school. If we do go slate, it is going to need to be thicker than standard and of very high quality. I will definitely get in touch with Camara and appreciate the lead. Quality suppliers are so important.

We will definitely have snow guards in place above the problem areas. The issue is more the amount of sun and days near freezing we get... Those holes fill up with solid ice unless mitigated with a heat source. I had always heard snow and ice removal from slate was a no go... Will the thicker tiles take some stomping and banging without too many pieces lost? I am concerned that once I have a bunch of slate hooks in place the problem will start to become exponential due to the unruly ice damming. Thanks again for your input. If you have further thoughts on this please indulge me. I will post this message over ar the other board, as well. Best, Dave