NELMA Grading Rules Interpretation --- Help Needed

[mattgancz]

I am in need of assistance in interpreting the NELMA Grading Rules for Northeastern Lumber.  I have spans and grades that I have determined using the American Wood Council Span Calculator.  Now that I am sawing said pieces, I need some help.

NELMA makes their gradebook available on the internet, specifically I looking at section 5: NATIONAL GRADING RULES, FRAMING & DECKING.

When I look at say Subsection 12.2 for No.1 joists, there is a bracket on the chart that says, "One hole or equivalent smaller holes per 3 lin. ft."  Does the length stated there also apply to the knot size at the edge and the centerline?  

The lengths are what is throwing me off; it doesn't seem to be explicitly stated.  What is allowed per length?  Section 13: INTERPRETATIONS OF THE NATIONAL GRADING RULE FOR DIMENSION LUMBER, offers some insight, but, again, at what lengths for which grade?

[Don P]

With knots I was taught 6" was enough separation but let's think about it. The failure around knots is not the knot, it is a slope of grain problem. Is the combination far enough apart that you have at least 2/3 of the grain staying within the stick for the required slope of grain length, then it is a #2. I just turned that on its head to think about it the other way, how much continuous fiber do we need to maintain a grade. 

The rules make it sound like you are looking at the surfaces. You are actually visualizing through the stick looking for good fiber and either how much is lost or how much is left.

Another way of looking at it would be to have defects spaced at least the member depth apart to be considered individual vs combined.

[mattgancz]

That's a great way to think about it, Don, thank you.  Six-inches is way closer than I would have anticipated.  Can you offer any references for grading other than the NELMA manual?  I am sawing joists, and for most I can use good sense, but there is a section that I want to be sure that I am meeting grade.  

[Don P]

This is a good related blog from SPIB (Southern Pine Inspection Bureau)
Total Measurement: Understanding Knots in Dimension Lumber | SPIB Blog | Southern Pine Inspection Bureau

NLGA manual links here;
Publications for Download – National Lumber Grades Authority (NLGA)

PLIB;
Standard No. 17 Grading Rules for West Coast Lumber | Pacific Lumber Inspection Bureau (plib.org)

WCLB;
Standard No. 17 Grading Rules for West Coast Lumber | Pacific Lumber Inspection Bureau (plib.org)
Those are probably identical, these guys seem to be in hot water more than anyone.

There are 7 rules writing agencies under ALSC (American Lumber Standards Committee), those were probably the most relevant. You can get a list of all agencies at ALSC's site. I trained at Timber Products Inspections, the largest agency but not a rules writing agency. There are probably some more publications there.