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Re: Double Layer Plywood Shear Wall

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Charles O. Laines, S.E.
In a message dated 7/6/2009 3:44:42 P.M. Pacific Daylight Time, RLHess(--nospam--at) writes:
The SEA of Southern California Code Committee has examined the use of staples in plywood shear walls and concluded that they are not satisfactory under reversing dynamic loading because of the generally non ductile mode of failure and questionable quality control and durability as compared to nailing.
I agree with those who would not recommend the "fix" by doubling the plywood.
Richard Hess, S.E.
-----Original Message-----
From: Tom Skaggs [mailto:tom.skaggs(--nospam--at)]
Sent: Monday, July 06, 2009 3:19 PM
To: seaint(--nospam--at)
Subject: RE: Double Layer Plywood Shear Wall

We did testing on double layered singled sided diaphragms.  Concept was retrofit of existing roof with an overlay of panels.  Attachment on top layer was with 14 gage staples, obviously to avoid splitting.  Results were favorable.  “Research Report 138” is available at our website, under the publications area.  Note that the edges of the top layer were intentionally staggered off the studs to prevent edge nailing into the framing.  So the 14 gage staples were shot through the ½” “under” panel.


My take is that, in theory it could work, but splitting of the framing with large nails seems like a very high likelihood.  I generally agree with the other folks who are not real crazy about this “fix”.






Thomas D. Skaggs, Ph.D., P.E.

Manager, Product Evaluation


7011 S. 19th Street

Tacoma, WA 98466

253-620-7479 (office)

253-620-7235 (fax)





From: Drew Morris [mailto:dmorris(--nospam--at)]
Sent: Monday, July 06, 2009 14:58
To: seaint(--nospam--at)
Subject: Re: Double Layer Plywood Shear Wall


I'm not sure this would work.  You could put the inner layer on with 8d nails and the outer layer with 10d nails staggered to miss the nails for the inner layer.  I don't this has ever been a tested assembly, so I am not sure you can go this way.  You might want to contact APA.  The other option is to put the sheathing on the inside over the gypsum wall board with 10d nails.  This is allowed under the 2006 IBC, not sure about the CBC.

ENGRLAINES(--nospam--at) wrote:

Contractor "forgot" the interior layer of plywood in a shear wall spec'd for sheathing on both sides. Wants to put double layer on the outside since the interior has been finished. I cannot find any restrictions in the Codes,  so I assume this can be done assuming the same requirements for sheathing on two-sides and no reduction in strength. Anything special to watch out for?



Charles O. Laines, S.E.



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