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Discussion Starter · #1 ·
I'm an old house gal, and know precious little about 1980s/90s construction. I'm helping a friend with a problem she's having at her 30-year-old house in California.

They've found excessive wood rot due to moisture, and she's telling me that her house has sheetrock used as an exterior sheathing (in place of plywood/osb) on her California tract house.

Has anyone heard of this before?

And any ideas when this practice was in vogue?

It's on a not-so-nice two-story tract house in a San Francisco suburb.

Thanks for any insight.
 

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Super Moderator
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Rose, I haven't heard of this practice anywhere around here. But I've been humbled here many times before with geographic differences.

Is she sure it's actually drywall used as exterior sheathing?

Our California guys will surely be here on this thread to advise.
 

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Always Learning
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Was the sheet rock paper black? I have seen it. Very limited in my area (Ohio), but I think the black paper was a very early moisture coating.
 

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Nouveau Eccentric
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My house has it, late 50's. SE Pa.
Water restant, fire retardant gypsum board, that is.

Still used today, although not so much around these parts anymore.
The trend now is more toward insulation board.

D.
 

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Quite possibly part of a fire rated assembly.

Especially in SF.

Bob, weigh in here.......it is after all your backyard:thumbsup:
 

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Goin' Down in Flames....
Highwayman
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Quite possibly part of a fire rated assembly.

Especially in SF.

Bob, weigh in here.......it is after all your backyard:thumbsup:
I've seen it more in commercial. It's to limit fire spread. I redid the siding on a 4-story commercial building in oldtown, and we installed exterior-rated type-x under the siding.

I live in the boonies, though, so I could certainly see it being used for the same thing in denser, urban areas.





Delta
 

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Butcher of wood and metal
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Have resided a couple of houses with it on here. Real pain to deal with when it is rotten. Stuff I have seen was only 2'X8' sheets, wrapped with a black paper. Normally have cut the bad stuff out and replaced with 1/2 osb.

Although I have not run into it yet have even hear of the stuff being used on roofs. guys would step though it when reroofing.
 

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The Dude
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How does that work? Wouldn't think it'd give any support to keep the wall from going out of square - diagonal support, isn't that one of the jobs of wall sheathing? Even blackboard is structural if you nail it enough.
 

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How does that work? Wouldn't think it'd give any support to keep the wall from going out of square - diagonal support, isn't that one of the jobs of wall sheathing? Even blackboard is structural if you nail it enough.
Lots of time the cornors had ply on them to keep things square.
 

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Highwayman
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How does that work? Wouldn't think it'd give any support to keep the wall from going out of square - diagonal support, isn't that one of the jobs of wall sheathing? Even blackboard is structural if you nail it enough.
Missed that in the original post.

The one's I've worked on had sheetrock over plywood.
 

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Discussion Starter · #14 · (Edited)
Lots of time the cornors had ply on them to keep things square.
Here are some photos.

This house was allegedly built in the early 1990s, and repair estimates have soared into the tens of thousands.

And yes, this was used in place of plywood - even at the corners. Strikes me as bizarre, but then again, this *is* Californie... ;)

Does anyone know what this product was called? And was it in use for very long?













 

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Nouveau Eccentric
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Lots of time the cornors had ply on them to keep things square.
Or individual 2x4's cut on the angle and placed between the studs as a racking brace.
Or, as I mentioned earlier, with the advent of the insulation board, a metal T strap fitted into a saw kerf cut on the 45* and nailed to the studs.

D.
 

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Gypsum sheathing is very unfortunate when you are not expecting it.
I found that on a 70's apartment complex I did a Siding/window replacement for. Same white paper as in your pictures. I have seen the black also..and black that began white...

DensGlass gypsum sheathing by GP is the norm on new commercial around here.
 

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The Dude
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Or individual 2x4's cut on the angle and placed between the studs as a racking brace.
Or, as I mentioned earlier, with the advent of the insulation board, a metal T strap fitted into a saw kerf cut on the 45* and nailed to the studs.

D.
The other guy mentioned plywood corners. Durrr!!! I've seen that done before with blackboard between without being nailed off to where it's structural. I've seen racking braces, but usually 1x and in old houses - inset into the studs.

What I HAVEN'T seen is these t straps fitted in to a saw kerf nailed to studs. What's that look like and how does it work?
 
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