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

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>Lynn said:
>I would be interested in the nature of the failures you observed.  Did 
>the nails pull through the OSB, or did the nails stay in the OSB but pull 
>out of the supporting member?  Or perhaps it pulled out laterally through 
>the edges.  Or perhaps their were other modes of failure.  Any specifics 
>on this would help.
>And did you observe any floor OSB failures?

        Our office uses OSB on almost every project without significant ill
structural effects. At an APA seminar several years ago we were told that
the tables in the UBC apply to plywood AND OSB diaphragms. Its my guess that
the shear values in the tables were actually lowered slightly so that OSB
could comply (any APA eavesdroppers, please correct me if I'm wrong). I know
that DSA/SSS (California State Schools) and OSHPD (Californai State
Hospitals) do NOT allow OSB on full California Building Code compliant
(Title 24) buildings at this time.
        The note we would typically use on our horizontal diaphragms, for
example, would be something like: 1/2" or 15/32" Roof sheathing APA C-D
32/16 with exterior glue fabricated in conformance to ICBO Report No.
NER-108 with 8d nails at 6" o.c. Boundary and Edge Nailing and with 8d at
12" o.c. field nailing - unblocked. The ICBO report referenced covers both
OSB and plywood. DSA/SSS and OSHPD requires plywood compliance to US Product
Standard 1-83 (or something like that). 
        I hope this proves helpful.
                - Terry

P.S. Our office resume is at for
anyone who would like more information.