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RE: 20 year wood study question

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Title: 20 year wood study question

March 15, 2007 

Reply: 20 year study


Thanks Buddy. I am not sure that this is the study I am referring to although it could be based on the PDF file for Chapter 06 of FPL’s document having been updated through 1998 and referencing the IBC. There is no real mention of the discussion related to the samples taken over the 20 year period starting in the very early 70’s and the reductions discussed are not clear as to the reasons based on the reduced availability of quality lumber that I thought was the point of the study and subsequent stress reductions used in the UBC codes.


Can anyone else provide a bit more clarity to confirm if this is a correct memory of the stress changes in the 94 or 97 UBC? I need to reference the document to a friend producing a wood text and I believe this was an important piece of data that needs to be footnoted or referenced.







Dennis S. Wish, PE

California Professional Engineer

Structural Engineering Consultant

C-41250 (Exp. 3/31/07)




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From: AWC Info [mailto:AWCInfo(--nospam--at)]
Sent: Thursday, March 15, 2007 6:16 AM
To: 'seaint(--nospam--at)'
Subject: 20 year wood study question



I think you are referring to the In-grade test program. Here's a link to an FAQ on our website that lists several resources:



John "Buddy" Showalter, P.E.
Director, Technical Media
AF&PA/American Wood Council
1111 19th Street, NW, Suite 800
Washington, DC 20036
P: 202-463-2769
F: 202-463-2791

The American Wood Council (AWC) is the wood products division of the American Forest & Paper Association (AF&PA). AWC develops internationally recognized standards for wood design and construction. Its efforts with building codes and standards, engineering and research, and technology transfer ensure proper application for engineered and traditional wood products.

The guidance provided herein is not a formal interpretation of any AF&PA standard.  Interpretations of AF&PA standards are only available through a formal process outlined in AF&PA's standards development procedures.


From: "Dennis Wish" <dennis.wish(--nospam--at)>
To: <seaint(--nospam--at)>
Subject: 20 year wood study question

March 14, 2007
Re: Trying to find documents about wood stress reduction
I am trying to locate information that is relatated to a 20 year study done on available wood used in construction and which was used in either the 1991 or 1994 UBC to reduce bending and shear values in the code. I know this goes back to the mid to late 90's but I am in need of a summary of the study and can't recall if it was done by the Forest Products Lab, AF&PA or AITC. Those of you in California may recall that the summary indicated that mature Douglas Fir harvested since the study started in the late 60's or early 70's concluded that choice lumber was no longer as plentiful as it had been. The 1994 UBC (if I recall) reduced material stresses or possibly the Modulus of Elasticity for lumber and also introduced more finger-jointed lumber into construction for stud use.

I can't recall where the study originated and would like to find a copy for reference. I remember that we discussed it for a while on the SEAINT List and it may have not have been adopted until the 97 UBC was codified.

If anyone has the document or any information that can lead me to the 20 year study, please let me know by e-mailing me privately or by posting back on this list.