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More Plywood Diaphragm ?'s

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In Table 2306.3.1 of the 2007 CBC (I would assume this also appears in the 2006 IBC), plywood diaphragms with nail spacing at less the 3” o.c. require 3x framing at all panel edges per note “c” and “d”.  In light of this, why are there shear values for both 2x and 3x framing members at panel edges and boundaries for nail spacings of 2.5” o.c. and 2” o.c.?  Is it because you could still have 2x framing at field nailing?  I’m thinking not because note “g” states that “The minimum nominal width of framing members not located at boundaries or adjoining panel edges shall be 2 inches.”  This leads me to believe that the intermediate framing member, as long as it is a 2x, does not play a role in the capacities of the diaphragm.


By the way, where is note “d” in the table?  I can’t seem to find it.  Anyway, what am I missing here?  I’m surprised I haven’t noticed this apparent contradiction until now.  Thanks for any help….


Doug Mayer, SE