Securing wall sheathing
I have two questions about securing plywood wall sheathing:
1) Many local contractors are now using staples to secure sheathing instead of nails. I never heard of that. I realize that it can meet local code, if properly installed, but will it do an adequate job of earthquake resistance in seismic zone C? (moderate risk) We also occasionally get high winds or tornadoes.
2) The house walls are wood studs above floor joists, with raised heel roof trusses above the studs. I thought that it would be best to use the plywood sheathing to help tie together the studs to the sill plate and studs to the trusses.
But the contractor I’m interested in using was planning to sheath the studs before raising the wall, and then add a narrow strip of sheathing separately to the band joist below (and the raised heel above). That wouldn’t help tie the studs to the anchored sill plate below. Is this acceptable practice?
I forgot to ask him if he plans to use staples for the roof sheathing, too.
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Replies
Debra,
The International Residential Code provides a fastener schedule for wall sheathing when staples are used (see Table R602.3, reproduced below).
When it comes to specific requirements for seismic areas and high-wind areas, it's best to consult an engineer.
I was taught that it's best if horizontal sheathing joints are planned so that sheathing can tie the rim joist to a wall, and so that sheathing can tie a second floor to either the rim joist or the first floor framing. I'm not sure whether that is simply best practice, or a code requirement.
Habitat for Humanity recommends the approach I was taught in its guide, "Building, Standing, and Bracing Exterior Walls."
In a Weyerhauser guide titled "Floor, Roof and Wall Panel Installation," I see no specific advice on the issue.
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Debra,
There are two issues when sheathing at the rim-joist. One is, as you mention, continuity to tie the structure together, the other is dealing with potential shrinkage of the underlying wood framing behind relative to the un-moving sheathing.
To me the best compromise is to run the plywood 1 1/2" higher than the top plate when sheathing the wall on the subfloor, and doing the same at the bottom of the second floor sheathing above. This leaves a narrower strip at the rim joist.
Martin, thanks for the link to the Habitat Framing Guidelines. Great pictures and it covers pretty much everything. If you have any others similar to it for other construction aspects, they're greatly appreciated. Cheers.
Make sure you follow the footnotes in the table & know if the design was based on the panel joint having blocking. A unblocked shear wall deflects 2.5 times of a blocked shear wall. Deflection = damage in earthquakes or wind loading