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Re: double sided shear walls

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Thanks Roger.

In a message dated 6/2/99 9:05:57 PM Pacific Daylight Time, 
73527.1356(--nospam--at)compuserve.com writes:

<< 
 
 Dennis,
 
 Southern Pine grading rules state that Kiln Dry is 15 percent moisture.
 
 WWPA grading rules (1991) states that "Moisture is removed from lumber 
either 
 by air drying or by use of special drying kilns."  [Section 4.00, WWPA 
 Grading Rules]  I think that this is the only place in the rules that "kiln" 
 is mentioned --- it certainly isn't in the glossary.
 
 Section 4.10 states, "... Except as otherwise provided, any lumber surfaced 
 at a moisture content of 15% or less *MAY* be stamped 'MC 15'." [Emphasis 
 added.]
 
 Supplement No. 3 to the WWPA grading rules gives the following definition: 
 
 "Kiln-Dried (KD) lumber is lumber that has been seasoned in a chamber to a 
 predetermined moisture content by applying heat."
 
 It doesn't say what that "predetermined" moisture content should be.  By the 
 definition, it could be 25 percent, if the lumber originally had 27 percent 
 moisture.
 
 PS20-94 has the same definition for "Kiln-dried" lumber that WWPA has.
 
 So, the only assurance that we have that lumber had been surfaced at less 
 than 19 percent moisture would be if it had an "MC 15" stamp on it or was 
 graded as kiln dried Southern Pine under the SPIB grading rules.  But even 
 then, the moisture content of the lumber may change as WWPA permits:
 
 "Restrictions on moisture content shall apply at time of shipping as well as 
 at time of surfacing, except that when lumber is shipped in open 
conveyances, 
 unprotected from the weather during transit, the seller is relieved of the 
 moisture restriction if the buyer is notified and consents to the method of 
 shipment."
 
 Since lumber degrades (and becomes less valuable) as it dries, you can bet 
 that most lumber is going to be graded at the moisture content it has at the 
 time that it is surfaced.
 
 I have seen lumber in covered storage in lumber yards here in Tucson that 
 literally had moisture running out of it.
 
 In addition, 5% of a shipment (1 of every 20 pieces) may actually be below 
 the grade stamped on it.
 
 These are also part of the reasons that I am opposed to LRFD for wood 
 construction.
 
 Hope this helps.
 
 A. Roger Turk, P.E.(Structural)
 Tucson, Arizona >>