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RE: Built-up 2x Wood Framing

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||-----Original Message-----
||From: Michael Bryson [mailto:bryson(--nospam--at)civil.ubc.ca]
||Sent: Thursday, September 21, 2000 9:26 AM
||To: seaint(--nospam--at)seaint.org
||Subject: Built-up 2x Wood Framing
||
||
||
||Sorry in advance if this is a stupid question, but whenever
||the code calls
||up 3x wood framing as a minimum (e.g. ledger diaphragm anchorage to
||masonry wall), can 2-2x be substituted?

No. At least, not as far as I know. I believe the requirement for 3x framing
is to provide adequate edge distance for higher loaded elements. (2)-2xs
would not achieve this.

|| Besides better strength and
||stiffness,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I don't agree with this statement. Regardless, I wouldn't use (2)-2x's in
any situation as a ledger for anchorage to a masonry wall (<-my own opinion,
not a code interpretation). Besides, if you have any significant vertical
load, the bolt "Q" values (sorry for using the antequated terminology, but
my keyboard doesn't have the "subscript perpendicular" key yet) have
demanded 4x ledgers in most of the masonry buildings I have designed.

The 3x's are coming into play at the wall ties (perpendicular to the wall)
and this is a GOOD IDEA! Many, many masonry walls have pulled away from wood
diaphragms during earthquakes. Also, make sure you develop the load well
into the diaphragm with straps and blocking across framing members if
necessary. The sub diaphragm design is extremely critical in the performance
of anchoring the masonry wall to the roof diaphragm. Of course, with the new
seismic coefficients, this can be a real PITA.

|| I think this would be cheaper too.

So, THAT'S why the contractors are calling me bitching about the 3x's. I had
NO idea :o).

Welcome to the 1997 UBC, Michael.

Regards,

Bill Allen, S.E. (CA #2607)
ALLEN DESIGNS
Consulting Structural Engineers
Laguna Niguel, CA
http://www.AllenDesigns.com
V (949) 365-5696
F (949) 249-2297


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