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Re: Anchorage of flexible diaphragms

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This requirement comes from the possibility of the wood splitting due to the combination of the diaphragm nailing from above (especially at a plywood joint) and the nailing or bolting of the wall anchorage connector.  A 2x4 sub purlin in a panelized roof wouldn't have much wood left after all of that nailing and bolting. I am guessing that your roof is not that large...I haven't seen many of those twisted steel straps used lately (especially in the City of Los Angeles).  You mignt want to see if your truss manufacturer has some pre approved anchorages for their products.

Howard Silverman 
Covert Operations, Inc.
Anchors, Adhesives, and Injection Systems

Hello all,

Quick question regarding UBC Section 1633.2.8.1.  Item 5 requires that
wood elements of the wall anchorage system shall have a minimum actual
net thickness of 2 1/2".  If I have a condition where a wood plate is
installed atop a masonry wall and trusses sit atop that plate, does the
2 1/2" requirement apply to both the plate and the wood trusses (typical
pre-fab trusses are only 1 1/2" thick)?  What about a condition where
wood trusses might be supported by a ledger (directly bolted to the face
of the wall) and steel twist-straps are placed along the side of the
truss top chord back into the wall?

This has probably been asked before, so I'll probably check the archives
as well.

Dave K. Adams, S.E.
Lane Engineers, Inc.
979 N. Blackstone St.
Tulare, CA 93274
PH:  (559) 688-5263
FAX: (559) 688-8893
E-mail:  davea(--nospam--at)

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