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RE: TJI Micro=Lam and Top Flange Hangers

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We recently ran into some nailing issues with microlam and timberstrand
products.  Our local TJI rep faxed us a table of "Guidelines for the Closest
Allowable Nail Spacing into Trus Joist Macmillan Residential Products"
revision date 1/18/99.  This table has more information than is contained in
Ner-126 and I suggest you get a copy if you regularly design with TJI
products. According to an engineer at TJI the splitting potential (into
glue-line or otherwise) is a function of diameter and penetration, with
penetration generally being the most critical.  The TJI engineer also
indicated that the spacings in NER-126 involve a fair amount of engineering
judgment.

Regarding the Microlam and Top Flange Hangers, the Nail Spacing Guidelines
table infers 10dx1.5" nails can be spaced (using judgement)somewhere between
3"to 4" - which does not appear to agree with the top flange nail placement
of the Simpson ITT hanger. Per Simpson's Composite Products catalog there
are 2 top flange nails on each side of the ITT hanger which means 4 nails
total into the glueline. (These nails appear to be staggered, but is not
clear if they meet the required 1/2" between rows.)Conversly, TJI shows in
their literature a detail of a top flange joist hanger with a Microlam. This
information is in the TJI catalog and also in the fold-out "cut-sheet".
Please refer to TJI detail H1 and the single joist hanger table. The only
requirement is that a minimum 3" MicrolamLVL is to be used.

Thus, it appears from TJI that the connection is acceptable, based on detail
H1.  However, that is not to suggest that there are not problems with the
connection from things like plywood nailing and sole plate nailing!

Respectfully,

Tom VanDorpe
VanDorpe Chou Associates, Inc.
Orange, CA







<<While I know of no specific restriction placed upon top flange hangers ( =
not to say they don't exist ),  microlam does have minimum nail spacings =
into the narrow face of the joist/beam,  Per NER-126 you are limited to =
8" centers for 16d,  4" centers on 10d, and 3" centers on 8d nails.  =
This also makes for problems if the beam has straps to the top for =
collectors and such.=20

Robert Shaffer
Santa Cruz,  CA>>