I myself having been trying to find the same information about lag screws. I
spoke with Phil Line at American Wood Council (AWC) this last week. Most all
the other comments you have received this morning are good information.
Phil did direct me to Appendix I of the NDS for additional info regarding
strengths. The first sentence of paragraph I.4 says "the designer should
contact the manufacturer(s) to determine fastener bending yield strength for
It goes on to explain what the fastener yield bending strength is and how to
determine this since the manufacturer typically does not have the Fsubyb
Fsub yb = Fsuby /2 + Fsubu /2
In the NDS Commentary is goes on to say that the "actual tensile stress in
the lag screw at the root diameter must also be checked when designing lag
screw connections for withdrawal".
I ordered and received a copy of the ASME B18.2.1 - 1996. Attached was an
addenda called ASME B18.2.1a - 1999. It has the dimensions and same note
about material strength.
I am working to find manufacturers of lag screws and strength information
they provide. I will keep you posted.
3448 Newland Court
Lakewood, CO 80227
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