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RE: Doug. Fir Lumber Grades

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Larry,
 
For a panelized roof system the owners and contractors probably did not use "No.1 and Better" grade of purlins and subpurlins. You may need to get up on a lift and find a few grade stamps to confirm the contractor used what was shown on the plans. Another way to confirm (E) lumber grading is to compare the actual size and position of knots to the WWPA or WCLIB lumber grading rules, but that requires a bit more skill and research.
 
Gerard has made a good point. You won't be able to make the (E) 1970's joists or purlins calc out for new loads using today's allowable stress values. You'll have to reinforce them or replace them for new loads. Check the beams and girders too. You may find elevated stress levels. Good luck.
 
Dave Gaines, P.E.
(626) 410-3631 cell
(626) 794-4117 home
(626) 584-4960 office direct line

gainesengr(--nospam--at)earthlink.net

From: Larry Hauer [mailto:lhauer(--nospam--at)live.com]
Sent: Friday, September 26, 2008 6:57 AM
To: Struct. Eng. Assoc.
Subject: Doug. Fir Lumber Grades

I am checking an existing "panelized" roof system, (cira 1970's), for the addition of equipment and screening on the roof. Ever since, I believe, the '94 UBC there have been stress values for doug. fir 2x and 4x for "No. 1" and "No. 1 and Better", and I have never understood when it is appropriate to use the "No. 1 and Better" values. Can anyone shed some light on this?
 
Thanks in advance,
 
Larry Hauer, S.E.


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