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Slate Roof Central Message Board » Ice and Water Membrane, Plywood, and other Controversies » "Premium" underlayment a likely cause of deterioration. « Previous Next »

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John_chan (John_chan)
Member
Username: John_chan

Post Number: 21
Registered: 08-2006
Posted on Thursday, April 16, 2009 - 11:56 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

From what I understand, there were 3 distinctly different areas in the Peach Bottom Slate region: Cardiff, Whiteford, and Delta. The quality of slate differed quite a bit between the 3 areas. Some peach bottom appears to be very similar in characteristics to Buckingham. There's another peach bottom area slate that turns slightly greenish, and a third one that turns slightly greenish and flakes.
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Kwhord (Kwhord)
Senior Member
Username: Kwhord

Post Number: 206
Registered: 10-2006
Posted on Wednesday, April 15, 2009 - 07:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

These are definitely soft all the way through on the top. Also, I've found a lot of slates with cracks that appear to be "rusted" on the inside. I'm guessing this is just natural imperfections and the roofers who laid the slate didn't cull them before they installed them.

The slates are very good on the exposed areas. If you break off the soft top, they ring true just like any other peach I've ever encountered.
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Joe (Joe)
Senior Member
Username: Joe

Post Number: 393
Registered: 07-2006
Posted on Wednesday, April 15, 2009 - 06:13 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Interesting. However, like all quarry areas, the slate quality varied from pit to pit. I have seen some Peach Bottom slates similar to what you describe - flaking, mostly on the back. When you scrape the flaking stuff off, though, it's still hard underneath. Could be just the quarry source that determined the quality of the stone.
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Kwhord (Kwhord)
Senior Member
Username: Kwhord

Post Number: 205
Registered: 10-2006
Posted on Wednesday, April 15, 2009 - 07:26 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I'm currently working on a slate roof that was installed in the 20's on a "modern" house. They were experimenting with a lot of new construction techniques. For instance the walls are veneer brick instead of a 2 wythe. On the roof they installed 12x24 peach bottom roof. The roof is a 5/12 pitch with 3 inch headlap. Before they slated the roof they installed what appears to be asphalt roll roofing. In addition to this, there are no vents in the soffit to move air through the attic.

The slates are in bad shape. Most of the exposed faces are still sound and very hard, but the tops and especially the backs are soft and chalky, and behave more like a black penn slate than a peach. We have cannibalized one whole side of a hip roof in the rear of the house to use for visible repairs in the front. Of the 2 squares we removed about half of the slates had to be tossed when culling them. The problem is always the top or the underside of the slate.

I know these slates shouldn't be deteriorating this fast. I've worked on much much older peach bottom roofs that are in better shape. They had a standard felt underlayment that deteriorated quickly allowing the roof to "breathe".

What do others think about the underlayment as a cause of deterioration?

I'm going to bring a sample of these slates to Frankfort for people to inspect, I'd like to know what others think about this.

Thanks.

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