Crown on dimension lumber
Crown on dimension lumber
(OP)
I'm trying to find out if the crown of lumber is dependent on its grade. I know that it's not part of the grading rules, but I was wondering if better graded lumber typically has less of a crown simply because of the nature of the grading rules (better lumber = fewer knots, fewer checks, etc.... - does this translate indirectly to less crown?).






RE: Crown on dimension lumber
RE: Crown on dimension lumber
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Crown on dimension lumber
1. National Grading Rules have requirements "warp" that vary with the grade.
2. Allowable warp is based on both the grade and the lumber length.
3. Warp is a measurement of crook, bow, cup and twist.
4. All of this is complicated requirement is spelled out in Section 752 of the National Grading Rules.
Here is a paper on Post-Frame Construction Tolerances that, conveniently, has the important part of Section 752 as Appendix "A".
http://bse
Note: Section 752 applies to dimensional lumber, too. Not just post-frame.
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RE: Crown on dimension lumber
Here is an excerpt showing the shrinkage pattern of the member relative to the position where it was cut from the log. The amount of cupping seen does depend on the species too as seen in the relative differences in the radial and tangential shrinkage values.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask