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Shrllc (Shrllc)
Intermediate Member
Username: Shrllc

Post Number: 37
Registered: 12-2008
Posted on Tuesday, January 20, 2009 - 04:34 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Simmilar old school, but different.
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Old_school (Old_school)
Member
Username: Old_school

Post Number: 23
Registered: 01-2009
Posted on Wednesday, January 14, 2009 - 10:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Isn't that what I said?
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Shrllc (Shrllc)
Intermediate Member
Username: Shrllc

Post Number: 32
Registered: 12-2008
Posted on Wednesday, January 14, 2009 - 04:44 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I would suggest ripping the shingles as well as the sheathing, plywood has no place under a slate roof. (OR) You could leave the plywood and strap the entire roof with 1 inch hardwood, rough sawn, hang your slate from that which would eliminate the intrusion of nails into the interior of the structure. I have resurrected several barns over the years, does your client intend on heating/cooling the space?
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John R. Crookston
New member
Username: Old_school

Post Number: 5
Registered: 01-2009
Posted on Monday, January 05, 2009 - 05:41 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

I believe that is going to weigh about 1,000# per square installed. One question I have relates to the air space. Is the barn being used for a home; and is it insulated? Normally there is no need for an air space if the whole inside of the structure is open. It "vents" itself whenever the wind blows through it. If it is a finished building and there is a finished cathedral ceiling inside, the air space makes sense. It is called a "cold Roof", and they work very well. You have to use a ridgevent and a soffit vent to make the system work however.

If you are concerned about the plywood surface, you could very well just install a layer of 1" lumber over top of the plywood and then install the slates over that. It would weigh more (the weight of the lumber) but you would then be nailing the slate over dimensional lumber instead of the plywood. Once the decking is on, just make sure and install the slates per the "bible" and I am sure you will be happy with the results.

If you are going to use the "cold roof", you are going to have to install a ridge vent too. One with external baffles works best, as it draws the air out of the space between the rafters (assuming there is an intake at the bottom). You could install a ridge vent and then cover it with a copper ridge roll if you liked. It would be functional, and the total thickness would be about the same as a saddle ridge made of slate. Make a small mock up and see what you think.
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Eric Braymer
Advanced Member
Username: Braymer

Post Number: 48
Registered: 09-2008
Posted on Monday, January 05, 2009 - 12:51 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

John, people here recommend real 1 inch wood decking rather that plywood because of the proven longevity of real wood.
On 100 year + roofs such as slate, you would not want a sheathing of thin veneer glued together as a nailing surface. Moisture and other factors can warp and separate this flimsy material, the slate Roof Bible and other Sources here explain this more thoroughly. If you want to minimize maintenance for as long as possible and (not to mention being more traditionally/ historically accurate), use rough sawn local 1 inch boards for a deck. The nails will stay put longer and if there is any moisture or extreme heat/dryness, real wood will noty separate and warp as quickly. As a good test, throw a piece of plywood in your back yard next to a piece of real wood on the wet ground in the sun, leave it there for a couple of months and see which one looks better.
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John Rich
New member
Username: Dave_wieboldt_architect

Post Number: 2
Registered: 01-2009
Posted on Monday, January 05, 2009 - 11:38 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Also we plan to use Vermont Royal Purple
Slate size: 20" x 10" 1/4" to 3/8" standard smooth
Weight: 8#'s per sq. ft.
Nails: 1-3/4"
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John Rich
New member
Username: Dave_wieboldt_architect

Post Number: 1
Registered: 01-2009
Posted on Monday, January 05, 2009 - 11:26 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Moderator/Admin Only) Ban Poster IP (Moderator/Admin only)

Hi,

I have a client who is interested in putting slate roofing on his barn which was built in 1717 (Goshen NY) The structure is made out of white oak and has asphalt shingles on there now. The structure seems to be in pretty good shape. I am designing the load of the new slate to be 8 # per sq foot. The purpose of the slate shingles is to minimize maintenance. I would like to ask a few questions and maybe you can help me out.

1. Air Space
There is existing plywood sheathing on top of the existing rafters, followed by spacers, then more plywood sheathing, then felt paper, and finally the asphalt shingles. My question is should I call to remove everything except for the existing sheathing on the existing rafters and install new plywood sheathing, then #30 felt paper, and then the slate? OR should I leave the first layer of sheathing and the SPACERS hence leaving an AIRSPACE? What is your recommendation?
2. Plywood
In your specifications you say “NO PLYWOOD ROOF DECKING WILL BE USED” why is that?

This is an historic building. So the idea is to not have the roofing nails come thru to the interior of the barn. So that’s what we are trying to accomplish with either having the airspace or the 2 layers of plywood (1) sheet existing and (1) sheet new.

If you can help me out I would appreciate it

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