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Re: WOOD: Visually Graded Lumber - "Ripp

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Chuck,

I'll have to check out the grading rules tomorrow, but IIRC, knot size is 
limited by grade and then adjusted whether the knot is in the middle of the 
wide face, in the edges of the wide face, or near the ends of the member.  A 
No. 2 grade is permitted to have larger and/or loose knots than a No. 1 
grade, which is less restrictive than a Select Structural.

There are some very little things that would cause lumber to be up- or 
downgraded, e.g., if wane is ripped off a No. 2 grade, the result could end 
up No. 1 or Sel.Struct.

What I haven't seen yet is the grading rule for that special grade called, 
No. 1 and Btr, that is used by the plated truss industry.

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

Chuck Utzman wrote:

. > IIRC allowable knot size is also related to the board size.  Dennis has 
. > previously suggested that simply designing one grade higher makes 
. > ripping acceptable, but I don't think that's correct (unless your 
. > specifying clear lumber).
. > Comments?
. > C. Utzman, P.E.

. > Roger Turk wrote:

>Bill,

>Basically, if you rip a piece lengthwise, you are repositioning the knots 
>with respect to the edges on the piece.  Knots which may have been center 
>knots could now be edge or spike knots; loose knots permitted in the center 
>could now be prohibited loose knots at the edges.  ASTM D245 describes where 
>in the piece knot provisions change.

>PS20-2002(? My copy of PS20 is in the office and I'm not) basically says very

>little about detailed grading of lumber, but specifies the agencies 
>responsible for writing the grading rules for various species.  For example, 
>WCLIB writes the grading rules only for Douglas Fir (Coast Region), WWPA 
>writes grading rules for other western species, SPIB writes the grading rules

>for Southern Pine, etc.

>I doubt if AWS has anything to do with it (AWC maybe, but not AWS <G>).

>HTH

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

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