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Re: WOOD - Engineered Lumber vs. Sawn Lumber

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The only question I have about engineered wood products (laminated veneer
lumber, parallel strand lumber, etc.) is whether it performs well (1)
over a long period of time, and (2) in adverse moisture conditions.

In today's wood framing marketplace, manufactured lumber is extremely
commonplace, and I don't think the questions is should we use it, because
that question is answered by market forces.  The products are used in
thousands and thousands of tract homes being built today.  Perhaps the
question we can help answer is "How can we improve the product."

After specifying manufactured lumber beams and joists for numerous tract
home projects in Souther California for large tract home builders, and
seeing the material on site, I feel comfortable that the material
performs well.  The shear strength is incomparable and can be especially
useful in header situations where a deeper member does not fit.

Mixing manufactured lumber with Solid Sawn Lumber:  typically, I have
found that floor systems with manufactured joists should have
manufactured flush beams, but to save money, drop beams may be sawn
lumber.  The decision, I believe is purely one of geometry and economics.
 For flush beams, equivalent depths are preferred for ease of detailing
and installation.  For drop beams, especially short spans, sawn lumber is
much more economical.

BTW - Be careful when specifying TJI floor joists.  Starting in November,
they will be changing their material content and the Moduli (plural of
Modulus?) of Elasticity on all (most?) of their products will be
different (less stiff in most cases, as I recall).  ICBO and other
evaluation reports are not available yet on the revised product lines. 
The old TJI Pro series has been eliminated and the new category of joists
is called "Pro series", under which there will be 150, 250, 350, etc.



Sharad T. Patel, P.E.