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Sheetrock Wall Bracing 1

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XR250

XR250

Structural
Joined
Jan 30, 2013
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Has anyone ever specified sheetrock shearwalls? I'm curious about the connection to the bottom plate.
Around here, 8 ft. walls use 93" studs and three plates for a total of 97 1/2". Assuming they hang the ceiling first, that leaves 97" of wall for 96" of sheetrock - so only 1/2" of lap on the bottom plate. Assuming they locate the screws perfectly, it allows 1/4" of wood and gypsum edge distance for the screw. I noticed on my new house construction that they did not even bother fastening the sheetrock to the bottom plate - likely for this reason. Fortunately, I am not counting on the sheetrock for lateral.
 
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Not advocating for the use of sheetrock for bracing, but is that really the way they install it on walls where you are? That would make the carpenter's job difficult with nailing the baseboards. And why would they bother to lift the sheets an inch, when they can just sit them on the floor? One more thing, don't they tend to install sheets horizontally now, in 12' lengths? Maybe that is regional.
 
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It is permissible by Canadian code to use sheetrock as bracing for shear walls, but there are specific rules for nailing and that would include nailing to the bottom plate. For low rise wood frame structures, it seems reasonable, but it may be prudent to provide plywood or OSB bracing when shear walls are spaced too far apart. Needless to say, some will squawk about that.

BA
 
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hokie66 said:
That would make the carpenter's job difficult with nailing the baseboards.
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Maybe , maybe not, but in my area, one sub does not care about the next sub. They always kick the can down the road.
hokie66 said:
And why would they bother to lift the sheets an inch, when they can just sit them on the floor?
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They have to so it abuts the ceiling board.

hokie66 said:
One more thing, don't they tend to install sheets horizontally now, in 12' lengths
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Yes, but each sheet is 48" wide (or tall depending on how you look at it) so two 48" sheets will give you 96" which leaves 1" at the bottom. No way they are going to use a 54" sheet and cut it down to 49" to remove that space.



 
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I'd rather have the gap at the top. That gets covered by the cornice. Don't you use a cornice? Maybe not, some prefer set corners.

Looked at the procedure used for fixing Gyprock, like your sheetrock. They use offcuts to lift the sheets 10mm off the concrete floor. Still allows for screwing the bottom, and for fixing the baseboards.
 
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XR - sucks for the contractor, but at those walls the construction has to be different. Not easy, and the typical residential inspection schedule rarely picks it up. So it takes some doing if you want to make sure it was done right.
 
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hokie66 said:
I'd rather have the gap at the top. That gets covered by the cornice. Don't you use a cornice? Maybe not, some prefer set corners.
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Most houses around here do not use cornices
phamEng said:
sucks for the contractor, but at those walls the construction has to be different. Not easy, and the typical residential inspection schedule rarely picks it up. So it takes some doing if you want to make sure it was done right.
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Yeahhhh, that's never going to happen [bigsmile]
 
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Good observation XR250. Follow up question... how does this work out any differently for a wood structural panel shear wall? I guess you can just nail to the lower of the 2 top plates? Is that right?
 
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XR - I despise gypsum shear walls. Something about the fact that the condition when they're most needed (a hurricane) is also the most likely time for damage to the roof (particularly single story houses with trees nearby, and to only a slightly lesser extent 2 story houses) which allows water in that can dissolve the shear wall. I realize it's still a little far fetched, but I don't like it. There's also the construction and inspection issues - unless there's a preconstruction meeting with the contractor, the drywall sub, and the city inspector, it's very unlikely that it'll come out okay in the end.

That said, I've worked with one contractor that did it right. They'd been burned on it on a small development, and figured out how to control their subs and work with the inspectors (or hire third parties for the shear walls) to get it done. They're the exception that proves the rule, though.

 
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gte447f said:
Good observation XR250. Follow up question... how does this work out any differently for a wood structural panel shear wall? I guess you can just nail to the lower of the 2 top plates? Is that right?
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That is my experience
 
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phamENG said:
XR - I despise gypsum shear walls.
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Agreed. Ironically, though, the unintentional gypsum shearwalls are likely providing the majority of the lateral resistance for a house. Especially those with that shitty cardboard "ThermoBrace" sheathing.
 
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1) I've been assuming 92.625" for precut studs which gets your over lap to at least 7/8".

2) If one wanted to build these walls special, what would be the best way? One option below that will, of course, still ruffle feathers and raise eyebrows.

c01_capz5x.png
 
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Precut "stud length" studs should be 92.625" once the additional 4.5" of plates are added it equals 97.125". The intent there is you should be using 5/8" ceiling drywall to prevent sagging between joists/trusses, and it should be installed first, leaving 96.5" of wall to cover. Fits an 8 foot sheet almost perfectly and you have at least about an inch of coverage at the bottom.

The trick, is getting them to screw the bottom of the sheets, because in my experience, last screw on the sheet is about 3" off the sheathing on the stud line.
 
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I think pre-cut stud lengths are regionally specific. 93" studs here are a true 93" just like 105" studs are a trus 105" I hear it varies in other locales.


jayrod12 said:
The trick, is getting them to screw the bottom of the sheets, because in my experience, last screw on the sheet is about 3" off the sheathing on the stud line.
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For sure. Although my trim guy was happy about that as it makes it easy for him to find the studs for baseboard since the sheetrocker did not mud the bottom screws.
 
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One one level, I kind of feel as though gypsum shear walls are so sketchy to begin with that maybe it doesn't matter so much if the fasteners don't make it to the plates. That said, I'm also not willing to be the one to go rogue on the usual detailing requirements.
 
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