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Re: [SEAOC] Re: Substitution of OSB for plywood sheathing

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David-
We have in our office NER-108, which was sponsored by the APA, which 
covers "Structural-Use Panels".  There are 3 types of Structural-Use 
Panels covered in this report, "APA rated Sturd-I-Floor", "APA rated 
sheathing", and "APA rated siding".  Our discussion has been about "APA 
rated sheathing".  
NER-108 specifically describes what qualifies as "APA rated sheathing".  
One of the descriptions is "oriented strandboard manufactured according 
to ANSI A 208.1."
One of several other products that falls under the catagory of "APA rated 
sheathing" is wood veneer (plywood).  This "APA rated sheathing" section 
also applies to "flakeboard", "waferboard", and "particleboard".
Accoridng to this standard, ANY APA sturctural 1 rated sheathing has the 
same structural peformance, not only for shear walls and horizontal 
diaphragms, but also for dead and live load capacities.
Any of these products can be specified as having exposure 1, exposure 2, 
or exterior exposure bonding resin.  
So theoretically, we all should be specifying for sheathing is:

15/32" exposure 1 (or exterior if you want) APA structural 1 rated 
sheathing manufactured in accordance with ANSI A 208.1.  (normally 
referred to as 1/2" plywood).

The contractor could supply any wood structural panel, including 15/32" 
plywood or 15/32" OSB, and it should not make a difference, you are 
SUPPOSED to get the same performance.
What I am looking for is real world practical experience from engineers 
who could help in evaluating if these product really do act the same.  I 
suspect that the OSB that came apart during the hurricanes was probably 
made with exposure 2 bonding resin.  If exterior exposure bonding resin 
had been used, this problem may not have occured.  But this is just a 
guess on my part at this point.
I guess the bottom line is that even though the NER says that any product 
with the APA rated sheathing stamp on it should provide the same 
structural performance, I am a little skeptical.  I am looking for some 
input from others who might have experience that suggests the NER report 
may be not be correct.
Thanks.

Lynn

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