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RE: Wood Grading Stamp

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I'm not an expert of lumber grading, but I briefly scanned Western
Lumber Grading Rules 2005 by Western Wood Products Association.  For
Structural Light Framing (2" to 4" thick, 2" to 4" wide) and Structural
Joists and Planks (2" to 4" thick, 5" and wider), the National Grading
Rules specify that lumber is graded FULL LENGTH.  I'm not familiar with
Timber grading, which very well may be a function of length of piece.

For lumber as listed above, cutting for length does not void trademark.
For a longer piece cut into two, one could assume that the two pieces
have a minimum grade as the original.  It is also possible for the
"better piece" could be regraded to a higher grade to improve recovery.

HTH,
Tom
-----------------------------------------------------------------------
Thomas D. Skaggs, Ph.D., P.E.
Senior Engineer
APA - The Engineered Wood Association
7011 S. 19th Street
Tacoma, WA 98466
ph: 253/565-6600
fx: 253/620-7235
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-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: Thursday, September 08, 2005 10:26
To: seaint(--nospam--at)seaint.org
Subject: RE: Wood Grading Stamp

David,

First of all, to some degree, once you started cutting that "ton of wood
for a backyard project", the grading stamp on you lumber (as opposed to
timber) becomes worthless.  Grading of wood is a function of dimensions
of the member in question (i.e. span and cross-section dimensions if I
recall correctly...been a while since I read a grading book and the
memory is not what it was).  An example is that one difference between
grades like No2 and Select Struct is the number and size of "permitted"
knots in the middle 1/3 of the span (i.e. where the bending stresses
would be greatest for flexural members).  Thus, if you bought a 20 ft
2x6 with a stamp for stay Select Struct and then cut it into 2 10ft
beams, then the grade stamp that you have is potentially no longer valid
(it might still be valid if the size and number of knots along the whole
length meet the requirements for the middle 1/3 of the span for Select
Struct).

<snip>

HTH,

Scott
Adrian, MI

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