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RE: WOOD - Engineered Lumber vs. Sawn Lumber

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On Wednesday, September 10, 1997 6:54 AM, Bill Allen, S.E. 
[SMTP:BAllenSE(--nospam--at)] wrote:
| Is there a special designation for the PSLs with camber? The
| last time I
| tried to specify this, the contractor told me that cambering
| was not
| possible.
| I believe one should be careful about specifying a camber=1.5
| *DL
| deflection. While this is appropriate (and required by Code)
| for roof
| members, it will leave a crown (theoretically equal to 0.5 * 
| deflection)
| on floor members.
| Regards,
| Bill Allen

Bill, the residential contractors are not aware of this, unless 
they do commercial projects. In fact, the same contractor that I 
had trouble with was the general for the project that I used a 
cambered Parallam. The yard told him that it was not available 
either until they checked with TJM.
You must specify a Commercial grade Parallam. Your TJM 
representative or a call to TJM 800-628-3997 will verify this. I 
was told that there is not special designation other than to 
specify commercial grade beam. They also recommended that the 
roof camber for the manufactured beam be specified as 1.5DL as 
is specified in conventional lumber.
I agree somewhat with your concerns for floor camber, but do not 
sufficient background to confirm. Camber in wood is intended to 
flatten out over the life of the member based upon an LDF of 
1.0.  Generally this relates to a ten year load duration cycle 
for a camber to work it's way flat.