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Date: | Sat, 14 Mar 1998 19:51:09 +0000 |
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Arcobaleno wrote:
> I'm doing a small house rennovation and addition - Can anyone give me either
> general or specific advice about using shakes or slate roofing - The project
> is in upstate new york and the new construction area is very small - approx
> 500 SF; the roof has a high pitch but it's not regular and pitches in several
> directions (don't ask). There is to be a small skylight/roof window. The
> construction is to be wood frame. The new addition butts up against an
> existing heavy timber frame house with a low pitch BUR. If anyone could
> recommend a manufacturer or good source of tech support, I would appreciate
> it. When I need Plastic Slate - I know where to go....
>
> Thanks a lot.
I don't get to play with shakes often, but slate, yes. First, you need to
accomodate the weight of the stone in the structural framing. There are various
methods of traditional slate installation. My preference, if it were my house,
would be to install 3/4" PT ply with a bituthene membrane, then install the slate,
making sure to use copper nails. This is not traditional. The bituthene produces a
1st barrier waterproof system. When you nail through the bituthene it seals around
the nails. You may also consider using a rosin paper slip sheet between the
bituthene & slate. There may be a need to accomodate thermal movement in the
slate. Only problem is that bituthene is slippery to work on, therefore you have
to consider logistics. Though this is the way I would tend to go, there are
problems to consider. A traditional means of slating is using horizontal perlins
which allow the stone to breath on either side... and related to vapor and
condensation on the interior. I have a French book for slaters that illustrates
this method in great detail. An American method is to use 30lb tar paper... which
allows a certain amount of vapor transmission -- and is not slippery to walk on.
If you go with a membrane beneath the slate you should consider if there is any
effect on durability. Slate roofs, if you use a good slate and good metal
flashings (well detailed) will last 100 yrs. It is difficult to say if using an
impermiable membrane will significantly effect the lifespan of the stone. What I
do find is that often the slate is in serviceable condition but that there is
water penetration into the structure, causing structural damage, which leads to
slate damage. I hope that a membrane would waylay the water penetration longer.
Stay away from Chinese slates. I have used Spanish slates... they are usually so
thin that they break to easily when installed. I understand that Pennsylvannia
slate is good... but I have also heard stories of it not being durable in
Northeast climates. My preference is NY/Vermont slate. Black slate is common. Red
slate is the most expensive. You can also have the slate cut... corners trimmed,
for interesting design effects and patterns. If you need more info I suggest you
come over to the shop and I'll show you what we have in the file. There is a
fairly detailed book that most of teh Northeast slaters will send to you for free.
I also prefer using lead coated copper flashings.
][<en Follett
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