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RE: existing wood floor joist bending stress

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Buddy Showalter is also on Light-framing Listservice from There are a number on Structuralist lists due to my involvement with WTCA and TPI. This is not to say that he or another from AWC or AF&PA do not participate in Seaint.Org, but that their time is limited and they tend to get inundated with list mail and find they can not reply as desired.

You might try reaching Buddy with your e-mail directly through AWC at Buddy_Showalter(--nospam--at) I am sure that those involved in this thread will respond faster in this manner.

If you are interested in participating in the light_framing(--nospam--at) list, please e-mail me for the link to the list subscription page. At the time being, I am involved in numerous family emergencies that are preventing my participation and while between calls to hospitals and families, I am indulging myself to a little R&R by reading list mail to get through the nights.

Please bear with those involved in AWC, AF&PA, WTCA, TPI, and other groups as they currently have their plate full and are not intentionally ignoring questions on the list – it’s simply a matter of priority and available timing.


Best Regards,



From: Joseph R. Grill [mailto:jrgrill(--nospam--at)]
Sent: Wednesday, September 06, 2006 6:03 PM
To: seaint(--nospam--at)
Subject: Re: existing wood floor joist bending stress


It would be nice if AWC would reply to the list or if Joseph will let us know what he might find out.  What I "think" I remember from a seminar is that the wood hasn't changed it is the way it is tested and that the new values should be used no matter the time frame.  So, I would be very interested in some explanation, again, from somebody in authority.

Joseph Grill

----- Original Message -----

From: Roger Davis

Sent: Wednesday, September 06, 2006 3:09 PM

Subject: Re: existing wood floor joist bending stress


Grading standards changed with publication of 1991 NDS. Wood graded by the pre-1991 standard has to be designed by the NDS rules in effect at that time. Wood graded by the post 1991 standard has to be designed by the post 1991 rules. You can confirm that with AWC Help Desk.


Roger Davis


SDS Architects, Inc.

Joseph Eribarne <jeribarne(--nospam--at)> wrote:

I am involved with a structure that was constructed in 1988. 2x12 floor
joists were designed for a tile flooring weighing 30psf. The allowable
bending stress for a repetitive Doulas Fir Larch joist was 1450 psi in the
1988 UBC. A flooring weighing 3 psf was applied (to save money).

The client would now like to apply a flooring weighing 10 psf, substantially
less that the original design. However, the present day code indicactes
that the allowable bending stress for this wood is now 1006 psi. The design
bending stress in the joist with the 10psf flooring is 1200 psi. What is
the allowable bending stress for the joist in the existing structure? Is it
the origial 1450 psi, resulting in a design stress of 83% of capcity or is
it 1006 psi, resulting in a 19% overstress, or is it something else?

Thank you for your attention.

Joseph Eribarne

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