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.

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.

The thicker ones will certainly take more punishment. I guess my question is about the ice buildup. Do the unheated structures also get ice buildup? If they don't and the "cold" roofs do, there is something missing. I guess most sheds that are not heated would not have the many traps for the snow etc. Ideally if the structure is strong enough and the thing is not leaking, it is best to leave the roof along and let it melt when it gets warm.

As to fixing broken slates, normally with the thicker ones I will use a copper nail and a bib flashing in the joint to waterproof it as opposed to a slate hook. Those are a bit stronger. You can always take apart an area if it gets bad and re-nail them and then just put the hooks at the high points. Make sure and carry the I & W up the walls on the dormers to above the level that nay water would back up.

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

Dave, First off, what kind of slate are you thinking of using, and what size? When you dry it in, if you are using an ice and water shield, make sure and install a layer of felt or one of the synthetic underlayments over the top of it so that it does't stick to the backs of the slates. You can fix the broken ones that way. Secondly, at the transitions, shorten the exposure down a bit so that you have 4 inches of headlap for the first few rows. Ice guards above those "trap areas, or perhaps an ice fence to hold the snow on the roof instead of crowding at the choke points. That will give you something to stand on if you have to go on the roof too. Lastly, IF you are thinking you are going to be shoveling it off, I would consider a bit thicker slate to stand up a bit more. I like to use Camara slate. Shawn Camara will watch the quality closely, and that is important! If you get imported slates, there is no telling what you will get. Kind of a crap shoot.

Visit Slate Roof Central if you want to talk to just slaters. Everyone is welcome there, but slate is the thing. JMHO