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Re: WOOD - Engineered Lumber vs. Sawn Lumber

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Dennis S. Wish PE wrote:

> While we are on the subject - Why is it that Trus Joist (or Lousiana Pacific
> or the other manufactered wood products companies) do not provide
> manufactured beams in conventional depths to sawn lumber. Why not produce a
> 5 1/2" x 11 1/2" member rather than an 11 7/8" beam. I have had to juggle
> details in order to fit a manufactured beam into locations where I could use
> a sawn lumber.
> Why, too, are Glu-Lam beams not made in conventional widths - ie, 3.5, 5.5.
> It would be a lot easier to get a beam in a wall that was 5 1/2" rather than
> 5.125?
> It would be understandable if the posts and studs supported these widths or
> depths, but I think it makes detailing more difficult.
>
> Here we go again?
> Dennis Wish PE

The way I understand it, 3-1/8" and 5-1/8" glu lams start out as 2 x 4 and 2 x 6
material prior to being finish planed.  The finishing process gets rid of all
the "uglies" on the side surfaces, including glue bumps at the laminations.  I
have seen 3-1/2" and 5-1/2" wide glu lams that were not "architectural grade"
used in place of 3-1/8" and 5-1/8" glu lams.  Check with your local glu lam
supplier and manufacturer.

Willamette Industries (Albany, OR)  has a line of I-joist compatible (IJC) glu
lams that work with the more proprietary I-joist  framing system at  3-1/2" and
5-1/2" wide net.  These work great when you need to "heavily" top nail (anther
weakness of the LVL and PSL) at straps, drag lines and the like.  The depths all
work with with TJIs.

As for the  non-conventional depths of I-joists:  it's my guess that the
manufacturers did this intentionally to keep it proprietary and encourage the
designer to use the full product line without easy substitution.  But that's
only a guess.  Maybe one of the manufacturers reps would like to comment?

Mark Codispoti