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Differences in Lumber Grades

Differences in Lumber Grades

Differences in Lumber Grades

I have been finding it difficult to locate a good explanation of the differences (both aesthetic and structural) between Structural Select, #1 and #2 lumber grades (especially for DFL).  Does anyone have any advice?

RE: Differences in Lumber Grades

Structural, refer to AF&PA (American Forest and Paper Association), National Design Specification for Wood Construction, where allowable stresses are given.  Each species and each grade has its own allowable value

RE: Differences in Lumber Grades

I haven't built in  lumber for many years, but just a comment.  If you have a situation where stresses dictate the use of something beter than #2KD you had better check on availability first. Grades like DSS or SS are only available in some sizes, if at all.

As for the asthetics, in the specs there are comments about edge condition and knot allowances.

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RE: Differences in Lumber Grades

Visually grading wood sometimes seems wierd....
It doesn't seem to match the stamp grade (?)

For instance, just recently looking at SPF 2x6's, I found some really attractive ones (straight grain, few knots, appearing 'strong') that were STUD grade STAMPED...
In contrast the STAMPED #2's appeared to have MORE defects?

In another example, I LOVE those hem-fir stud 2x4's; they're so many that are always so straight, have less knots, appear and 'act' stronger than the -- supposedly superior -- SPF counterparts...
Somehow, I almost feel there is something wrong...

Could it be, that, among the stacks of 'studs', lies many that actually might be equivalent to higher grades?
(i.e., that the 'average' of them are 'studs', but that there are some that are much better quality)?
If so, is it because that they are difficult (or it's not cost effective enough) to separate them?

RE: Differences in Lumber Grades

Material that is stamp stud grade is required to meet or exceed the grade restrictions for stud grade.  As you indicated cost effectiveness is a major reason the mills don't pull out the higher grades.  

In general a mill will have orders for a large volume of stud grade 2x4's.  In a case like that they may schedule time for stud grade 2x4 production.  So during that time they cut 2x4's to fill out their orders.  As that material goes down the line the grader looks it over and gives it a grade mark for stud grade or a mark indicating it will not meet stud grade.  The mill is trying to fill their stud grade orders so they aren't checking the material to see if it will make a higher grade such as #2 or select structural.

Practice varies from mill to mill so at another mill they may be running 2x4 production and at the same time checking for higher grades that can be pulled out and sold for a higher price.  

Also remeber that structural lumber is graded for strength not apperance so pretty lumber may have lower strength then lumber with larger knots.

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