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OSB & humidity

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There was also an article in Professional Roofing Magazine, April, 2000, 
about the same subject that raised the hackles of APA.  (www.nrca.net)

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Gary wrote:

>>Here's a memo from Prof Wayne Wilcox of UC FPL on a paper by Profs Quinglin 
Wu of LSU, FPL and Otto Suchsland of Mich State in Wood and Fiber Science:

"In a recent study ( W&FS 29(1) : 47-57, 1997) Southern Pine and Aspen OSB 
were subjected to high humidities, at MC's of about 20%, resulting from high 
humidity, not contact with liquid water.  Total thickness swelling was 16 
-22% in SP & 20-26% in Aspen, resulting in losses in bending strength and 
stiffness of about 60-80% .

Since a linear relationship was found between moisture content and strength 
loss, extrapolation reaches 100% strength loss at MC's only slightly above 
the fiber saturation point, reached easily when liquid water is present."

OK.  Check it out.  The grapevine has it that there are class-action lawsuits 
already.  Lawsuits can be fun, depending on your entertainment budget.

Bring back diagonal sheathing.

Gary<<