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Jason4z (Jason4z)
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Username: Jason4z

Post Number: 3
Registered: 08-2014
Posted on Sunday, August 03, 2014 - 02:09 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Here is a photo of the slate I have for my roof in Flagstaff. What grade do you think this is?
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John_chan (John_chan)
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Post Number: 150
Registered: 08-2006
Posted on Friday, August 01, 2014 - 07:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

That's true with low grade slate. As John said, use a good Vermont, Canadian or Virginia slate and you won't have that problem. These slates have been used for over a century in climates that are at least as bad as Flagstaff without any problems. The problem is usually with the grade of slate, as well as the installer. Any installer that would put on a low grade slate in that climate does not know anything about slate roofing.
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Old_school (Old_school)
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Post Number: 1076
Registered: 01-2009
Posted on Friday, August 01, 2014 - 05:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I would almost bet that they are using the Brazilian slates down there and they are doing what they do when they bring them up to the Midwest...;They fall apart! If they would use them 70 miles away from Flagstaff where it is just hot, I would bet there would be no problems. tell them to use some Vermont slates or some Buckingham Virginia slates and the problems would disappear...if they install them correctly. Good rock is good rock and the crap is crap and it really doesn't matter where it comes from. A lot that is shipped into the states is real crap though. Hey, it is "cheap"
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Jason4z (Jason4z)
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Posted on Friday, August 01, 2014 - 01:56 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Im building a home in Flagstaff AZ. Everyone in this area tells me the same thing that I will have issues with my slate no matter how perfect the insulation is because Flagstaff gets a 40 degree temperature swing and strong sun. They tell me that the freeze thaw cycle will damage the slate and I will soon have problems and its not the installation that is the problem. They say all slate roofs in Flagstaff have constant problems. I have read the slate roof bible and basically know what to look for but I cant find any info if the slates actually break and crack due to massive freeze thaw cycles. Is there any thing I need to worry about and any truth to what everyone i Flagstaff is telling me?
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Joe (Joe)
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Username: Joe

Post Number: 775
Registered: 07-2006


Posted on Saturday, April 27, 2013 - 08:12 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Why not a slate roof with a soldered copper or double lock standing seam copper snow apron where the ice damming occurs, and extra headlap on the slates above the snow apron?

http://www.slateroofcentral.com/install_snow_aprons.htm

http://www.slateroofcentral.com/videos.html#snow_apron
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Old_school (Old_school)
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Username: Old_school

Post Number: 976
Registered: 01-2009
Posted on Thursday, April 25, 2013 - 07:39 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

No wonder I was confused. That is easy to do to me though. You may incorporate a heavy duty heat cable with an ice fence above the area with the cable snaking through the worst areas to keep the water flowing when it gets too nasty. If you know the problem areas going in, an ice cable that you can turn on and off will help a lot. Is this a year round home, in other words, will it be kept very warm all the winter months, or will the heat be turned way down a lot of the time when no one is there?
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Daves111 (Daves111)
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Posted on Wednesday, April 24, 2013 - 11:45 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Hey Grapier and Old School... Grapier is the owner on the same project and Old School, you did answer me on the Roofers Coffee Shop - Thanks.

Here is the original post - I could use some help here on this -

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 homes 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

I have read some of the discussion here on ice dams and just want to reiterate that the ice dams where we are at are tremendous in scope regardless of cold-roof, insulation, etc. This is due to the very long winter, UV at elevation, the cut up nature of roofs on custom homes which causes many areas to receive lots of sun directly above areas that are shaded for months on end, and many days of freeze/thaw cycle. In short, there will be, at some point in the roofs life, pooled water that freezes/heaves/thaws cyclicly at the transitions and in some of the valley areas. All comments appreciated. In the end - the only real question is - "Is this a good idea for the Northern Rockies or will we be experimenting to some degree?"
Thanks all. (Grapier - I'll swing by your build site next week to discuss in person with Nick. Our other potential concern is weight... Slate + 400" per year + cold roof = ??? on the framing)
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Old_school (Old_school)
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Post Number: 975
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Posted on Wednesday, April 24, 2013 - 09:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Grapier, I think I answered that for you on the coffee shop. Give me a call if you want.
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Grapier (Grapier)
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Posted on Tuesday, April 23, 2013 - 12:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I am building a log cabin in Southwest Montana, roof pitch is 12/12. Can anyone advise me on the feasibility of using slate on this project. We get about 400 inches of snow per year and winters are cold down to -30 intermittently.
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Joe_jenkins (Joe_jenkins)
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Post Number: 44
Registered: 10-2010
Posted on Tuesday, November 01, 2011 - 11:57 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Gravity doesn't shut off during an ice dam situation. The water is still be pulled downhill. The only time headlap doesn't matter is when it's flat, not sloped. That's one reason why slate roofs should be steeper rather than shallower in slope.
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Old_school (Old_school)
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Post Number: 731
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Posted on Thursday, October 27, 2011 - 08:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Precisely,, but that is the same thing as increasing the head lap. No matter how you install the slates or shingles for that matter, if you get a heck of an ice buildup and the water ponds behind it, you will have leaks. The reason you don't normally see that much of it on a slate roof is that they are normally so steep. If you get down to about 6/12 pitch with no provisions for an ice barrier, you will get leaks.
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Lv_pa (Lv_pa)
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Post Number: 34
Registered: 05-2007
Posted on Thursday, October 27, 2011 - 05:19 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I guess the point is that the increased headlap makes it harder for the wind to blow the pooled water up underneath the slates. But I was kind of wondering the same thing myself. Maybe it would also help to use taller slates for the starter course and first few rows.
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Sniffingratty (Sniffingratty)
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Registered: 09-2010
Posted on Thursday, October 27, 2011 - 08:16 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Yes, but in an ice dam situation the water is pooing and not running downhill, so headlap should make no difference, right?
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Joe (Joe)
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Post Number: 649
Registered: 07-2006
Posted on Monday, October 24, 2011 - 11:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

The ice builds up at the eaves because the ice and snow melts on the roof surface and runs down the roof, freezing again at the unheated eaves. The ice builds up at the eaves and causes a dam that can cause the ice to extend up the roof several feet, especially in low-slope situations. Increasing the headlap makes it harder for water to get through the shingles. As long as there is slope, the water will be trying to run downhill, hence the value of headlap. If the roof is flat, increased headlap won't make any difference, nor will any headlap.
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Old_school (Old_school)
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Post Number: 730
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Posted on Saturday, October 22, 2011 - 07:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Slate works just fine with the ice buildup; exactly like shingles but it will obviously last longer. You are not going to have ice all the way up the roof, only where the heat stops and the overhang starts. If you have a long overhang, the ice will start where it meets the house. A double layered felt with plastic roofing cement between the layers will work, as will a layer of Ice and Water Shield as long as you put some felt or one of the synthetics over it to keep it separate from the slates. It makes it a lot easier to fix if they break. Joe pointed out the "hazards" of the I & W, but myself personally I don't consider it any worse than getting tar all over ones self. That is my opinion though. The steeper the pitch, the less likely you are to have leakage from the buildup. that is the big advantage of increasing the headlap as it give the water that much farther to travel before it can go over the top of the slate and get into the system.

Understand though, if you get enough water standing on the roof, eventually it is going to find it's way into the building. Heck, swimming pools leak sometimes and they are designed to hold water.
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Sniffingratty (Sniffingratty)
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Posted on Saturday, October 22, 2011 - 01:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I was thinking to do 5" headlap, but then I couldn't figure out how that would help, as I described in my first post. Old school agreed with me, but you disagree?

The other thing that I'm wondering is: if the ice damming is from weather conditions couldn't it occur anywhere on the roof, like you said you had it 6' up on the roof. So wouldn't I need the felt and cement layer over the whole roo
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Joe (Joe)
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Post Number: 648
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Posted on Saturday, October 22, 2011 - 12:23 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Here's a link to a lot of our slate roofing video clips: http://jenkinsslate.com/messages/messages/5528/5528.html?1318801217
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Joe (Joe)
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Post Number: 647
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Posted on Saturday, October 22, 2011 - 12:22 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Did you watch our video on how to install ice-dam resistant slate roofs? http://www.slateroofcentral.com/videos.html#eaves.

Also, I wrote an article about IWS in a recent Traditional Roofing pointing out the carcinogenic content: http://www.traditionalroofing.com/TR8_cancer.html
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Sniffingratty (Sniffingratty)
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Posted on Friday, October 21, 2011 - 08:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I am in Syracuse NY, sounds like slate is not the right material for this climate :(

I could put ice and water shield all the way up the roof and it would be good for 25-30 years, but then what, take the slate off and re-do it?

So if I understand yall correctly the only way to go in this climate is with a very steep pitch, or metal?
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Old_school (Old_school)
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Posted on Friday, October 21, 2011 - 07:39 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

In Western Michigan we get the lake effect snow bands going and they don't quit. Quite a bit like Buffalo New York at the end of lake Erie. The snow tends to be light and fluffy and it can get 6 to 12 inches a day for days on end. That is the perfect environment for the ice buildup as it compacts and turns to ice in a hurry. a lot of people try and shovel off the roofs and some are killed every year from falls or falling ice.

There is a lot to be said for constructing the roof so that it won't support the ice buildup through proper ventilation, and also through an ice barrier beneath the roofing that will stop the penetration of water into the envelope of the building. You have to know what you are doing though.
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Joe (Joe)
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Posted on Friday, October 21, 2011 - 02:47 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

We had ice damming 6 feet up the roof last winter. It is a 4:12 slope. Lower slopes have bigger ice damming issues, especially if there are other roofs draining on to them. In NW PA we have had three bad ice dam years in a row. The 30 years prior it has not been a problem.
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Sniffingratty (Sniffingratty)
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Posted on Thursday, October 20, 2011 - 07:08 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

So you think I will be ok without a snow guard as long as I ventilate and insulate properly?
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Old_school (Old_school)
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Posted on Thursday, October 20, 2011 - 06:17 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

If it is warm enough to melt the snow and ice on the roof OUTSIDE of the attic, the problem will disappear quickly and on it's own. With the ventilation and insulation, you want to make sure that the insulation doesn't block off the ventilation at the eave, and also that the insulation does not touch the bottom of the roof deck.
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Sniffingratty (Sniffingratty)
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Posted on Thursday, October 20, 2011 - 10:01 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I am going to ventilate the roof along with insulation, which should take care of melting from heat from the house. but I'm still worried about melting and re-freezing from weather conditions, or do you not think that will be a problem?
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Old_school (Old_school)
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Post Number: 725
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Posted on Tuesday, October 18, 2011 - 08:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

One thing at a time. On a building with heat, normally the attic temperature is going to be above freezing. If you insulate and there is not enough air flow or worse yet no air flow, it is going to exacerbate the problem. The ice forms at the bottom of the roof where the heat stops and the overhang starts. If you have a 6' overhang, it will start at the 6' line. The heat inside the attic melts the snow on the roof and it turns to water, running down the roof til it hits the cold over hang. It will freeze every time. It continues to build up as the water continues to run down, and eventually it will make a dam that will cause the water to back up behind it. I have been n roofs where I stepped into 12" of water behind the ice dam. No shingle or slate roof is designed to stop standing water, and they will leak. Some type of water barrier beneath the shingles or slates will help to stop the leakage, but it will not stop the buildup. Ventilation is the key, because if you can keep the attic cold, the snow will not melt and snow is easier to deal with than ice. Multiple ice guards or an ice and snow fence on the bottom of the roof will keep the snow on the roof until it is warm enough so that it all melts at the same time. Side walks beneath the overhang are a bad idea. Consider moving the traffic pattern.
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Sniffingratty (Sniffingratty)
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Posted on Tuesday, October 18, 2011 - 07:35 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I am talking about a slate roof. So you are saying that I will not have to worry about ice damming because when it warms up and starts to melt (and pool) it will slide off? However I will have to worry about falling ice chunks.

If I understand you correctly then it seems that I should go with copper snow belt with snow guards on the section that is above the sidewalk, and sections that I don't have to worry about falling ice hitting people I can just go with slate?

Last year I had plastic on the roof and the snow slid onto the sidewalk making giant impassable mounds.

One other thing that I don't fully understand is why ice damming only occurs on the bottom 3ft. of the roof. I understand that that is usually where the heat from the house is released, but I thought that ice damming could also occur from rapid heating and cooling like we have sometimes in the winter. I am going to insulate like crazy and ventilate the roof deck, so I am more worried about ice damming from weather conditions. Why would it only occur on the bottom 3ft of the roof, or am I mistaken about that?
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Old_school (Old_school)
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Post Number: 724
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Posted on Monday, October 17, 2011 - 07:21 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Shingle roofs have a rough surface with plenty of area for the ice to bite into, plus they will stay wet and the ice will form on them. Slate will do that too, to a lesser extent and metal to an even lesser extent. The question of snow sliding off then depends on the surface you are talking about.

6/12 is not steep for slate, and I am sure that some of the snow will become ice at the bottom and stay there until it get warm enough for it to go all at once. I don't think that some snow sliding down will harm much, but it becomes ice, look out. What happened last year?
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Sniffingratty (Sniffingratty)
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Post Number: 12
Registered: 09-2010
Posted on Monday, October 17, 2011 - 05:26 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

One more thought: is it true that if the pitch is steep enough then the snow will fall off of the roof before it has time to ice dam? My pitch is 6:12, would that be enough to shed the snow and not require a snow belt?

If so, then I would just put the snow guards above the 3ft danger zone and it would be ok? One part of the roof does have a sidewalk under it tho, so that may pose a problem.
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Old_school (Old_school)
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Post Number: 723
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Posted on Thursday, October 13, 2011 - 07:37 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

You've got it exactly. You may just want to put down a couple of layers of roofing felt with some plastic roofing cement spread between them or perhaps a layer of ice and water shield and then a layer of felt or some of the synthetic underlayment over it and then slate away. the increased headlap will shed the water better, but ponding water will eventually find its way through. DON'T caulk between the joints.
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Sniffingratty (Sniffingratty)
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Post Number: 11
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Posted on Thursday, October 13, 2011 - 06:01 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I was going to install a snow apron to prevent the ice damming, but it is going to be too expensive so I guess I am going to go with 5" overlap. I just have one question:
How is it that water will not trickle through the slates even with the overlap. I understand that if the water is running off of the roof there is no problem because the slate underneath the crack sheds it. But if the water is trapped in a pool on the roof what is to keep it from flowing sideways to the crack inbetween the slates below it, and then sideways again to the crack inbetween the slates below that one? It seems that even with 5" headlap the water will zigzag through. Is there something that I am missing? Should I caulk in between that slates?

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