Lumber grading - the very basics GUESS THE GRADE

[jeff...]

Hardwood Lumber Grading - the very basics

1) Calculate Board Feet (BF). Measure lumber width, thickness and length. One BF is a piece of lumber that is 1” thick 12” wide and 1 foot long or its equivalent. The formula to figure board feet is as follows:

Thickness * Width * Length
---------------------------- = BF
12
It’s best to round your measurements for simplicity sake. For example you find a piece of Oak lumber that measures 2 1/8” thick, 7 3/4“ wide and 8’ 3” long. Round down the thickness to the nearest 1/4”, width to nearest whole inch and length to the nearest whole foot. In our example we’ll make this piece of oak lumber a thickness of 2 inches, a width of 7 inches and a length of 8 foot, by rounding all three measurements down as specified above.

Thickness (2) * Width (7) * Length (8 )
--------------------------------------- = 9.3 BF
12

2) Calculate Surface Measure (SM). SM is nothing more than the surface measurement of one of the two faces of a piece of lumber. It’s calculated by measuring the width and length of the lumber and dividing the resultant by 12. If the SM calculated winds up to be a fraction, round the fraction to the nearest whole number, (.5 and above up, .49 and below down). Take note that thickness is not taken into account when determining SM.

Width * Length
--------------- = SM (rounded)
12

Again it’s best to round down width to nearest whole inch and length to the nearest whole foot. For our example piece of oak lumber, it measures an actual of 7 3/4” wide and 8’ 3” long. Again for calculation simplicity, we’ll round the width down to 7” and length to 8’

Width (7) * Length (8 )
----------------------- = 4.67 SM (round up) = 5 SM
12

3) Calculate Cutting Units (CU). A Cutting Unit is one inch by one foot or its equivalent. Again note, lumber thickness does not play a role in calculating CU. The formula for CU is merely the multiplication of the width and the length of a piece of lumber. The result is the number of cutting units contained within that piece of lumber. As we’ll see later SM and CU are vital in determining the grade of the piece of lumber.

Width * Length = CU

Similar to SM and for simplicity sake, it’s best to round down the lumber width to it’s nearest whole inch and it’s length to the nearest whole foot. So we’ll multiply 7 x 8 and arrive at 56 cutting units.

Width (7) * Length (8 ) = 56 CU

First a word about defect, for the purpose of my understanding the very basics of hardwood lumber grading, we’ll consider any knot, check, split, dote, hole, wane, worm holes, etc… a defect. What we are after is clear cuttings out of a piece of lumber. The grade rules cover defect and what’s allowed and what’s not per grade and species. Remember when reading this, that it’s my intent to cover grading rules details. Details regarding hardwood grading rules can be found in the latest release of the National Hardwood Lumber Association Hardwood Grade Book. http://www.natlhardwood.org/pdf/2007_Rules.pdf

4) Understand the basics of FAS grade requirements.

* FAS minimum board size is 6” wide by 8’ long. Any board irregardless of how clear it’s faces may be can not meet a FAS grade unless it meets or exceeds the minimum board size.
* A FAS clear cutting can be no smaller than 4 inches wide by 5 foot long or 3” wide and 7’ long. A cutting can be larger, but must be at least be these sizes.
* FAS number of allowable cuts is SM divided by four with a maximum of 4 cuts. The result is rounded down to the nearest whole number (drop any fractions)

SM
---- = FAS allowable cuts (Max 4)
4
* FAS CU Yield is SM times ten. This is the minimum allowable clear wood form the piece of lumber. For a board to make FAS ten twelve’s of it’s wood must be clear and be contained within the minimum FAS Clear cutting size and be cut in the FAS number of allowable cuts


5) example. The example below represents a piece of lumber that is 1 1/8” thick at it’s thinnest section. The black areas represent it’s poorest defective face and the dashed line is where the board would be cut to yield it’s greatest number of clear cutting units. Does it qualify for a FAS grade?

5-1) flip board to it’s poorest side, All hardwood is graded according to it’s most defect ridden face. Except for F1F and Select grades which I'll cover later, if I don't fall asleep first.

5-2) First calculate Board Foot (BF)

Thickness 1 * Width 10 * Length 8
---------------------------------- = 6.67 BF
12

5-3) Calculate the surface measure (SM)

Width 10 * Length 8
--------------------- = 6.67 SM (7 rounded)
12

5-4) Calculate the number of cutting units contained in the example

Width 10 * Length 8 = 80 CU


5-5) Calculate number of allowable FAS cutting to make grade

SM (7)
----- = 1.75 FAS allowable cuts (1 fraction dropped)
4

5-6) Calculate FAS CU Yield required

SM (7) * 10 = 70 FAS cutting units required


5-7) calculate CU of clear cutting, Width 9 * Length 8 = 72 Clear Cutting units

In this example with one allowable cut the board has made the FAS Grade – this is assuming both sides of the board are clear and contained in the clear cutting units made by the single allowable cut. Also note if both edges were clear and there was defect within one foot of the end of the example board, it would also make FAS grade with a width of 10 and a length of 7 resulting in 70 clear cutting units and matching the minimum FAS CU required.

[DaveO]

Thanks Jeff, that is excellent infomation to know, and you explained it well.
Dave

[Bas]

Jeff, thanks for the info. Really helpful having this all together in one place. Readable post too! I usually I get lost right after the author states "we'll keep it simple"

[jeff...]

You guys ever read the rule book - it makes my head spin... And I'm used to reading some pretty technical garb. What I'm trying to do is pull out the very basics and cobble it together in some readable format that I can understand.
It's by no means meant to cover the grade rules in detail, it's more how I understand the basics after reading the rule book. So anyone please feel free to correct me if I'm wrong, I could be way off base...

[sapwood]

Nice Jeff!
How about submitting that as a PDF file for the Download Library?
'Cause I'll probably forget it by this evening

Thanks,
Roger

[FredP]

Originally Posted by sapwood

Nice Jeff!
How about submitting that as a PDF file for the Download Library?
'Cause I'll probably forget it by this evening

Thanks,
Roger

forget what?????????????? oh yeh! I forgot... must reread so i can forget again! thanks for the reminder to forgeter jeff. good info buddy!

[McRabbet]

Originally Posted by sapwood

Nice Jeff!
How about submitting that as a PDF file for the Download Library?
'Cause I'll probably forget it by this evening

Thanks,
Roger

I completely agree with you Roger! Or, perhaps it should be extracted from here and added as a new entry in the FAQ Forum.

[Ray Martin]

Originally Posted by sapwood

Nice Jeff!
How about submitting that as a PDF file for the Download Library?
'Cause I'll probably forget it by this evening

Thanks,
Roger

Jeff,

This is a terrific reference. I agree with Roger. This should be in the library. Thanks for posting this.

Ray

[Kyle]

Jeff,

Under #1.. Hardwood grading rounds up as well for width the thought process being that some will be over and some will be under average over volume is the median. I have found that commercial product purchased for resell is pretty spot on and uses this methodology.

EX. 7.75 is greater than 7.5 and rounds up to 8" . 7.4 would round down to 7"

another way to do it with a calculator is by inches..
2" x 8" x 8' or

2" x 8" x 96" = 1536 inches then divide by 144 = 10.67 bf

The wholesalers and high volume guys measure this way. We small sawmill guys are generous.

Under #3

A board that say is 12" wide and 1' thick and 9 feet long may have a defect (knot or hole) on an edge and still be considered FAS due to the cutting units.

I always advertise as SELECT due to the stringent FAS criteria.

Also Walnut and cherry sap are NOT considered defects.

Determination of Grade is not easy and the graders go to school for certification for the short course or whole enchilada.

A new grade that seem to be arising more often is FAS 1F (1 clear face)

[bonewood]

Answer my PMs on that other site

[Grgramps]

Jeff, I think we all benefit by understanding how board feet are calculated. (It's not like buying 5 lbs of potatoes.)

Is there a difference when calculating board feet of green wood and wood that has been dried? The reason for asking is because when I bought from Gennetts in Asheville they made the calculation to account for the shrinkage of the kiln dried lumber.

I haven't experienced this elsewhere so I wonder if this is just their policy? It has probably been a couple of years since buying from them after finding other lumber sellers did not follow that method. I can't say how they presently calculate.

Roy

[jeff...]

Originally Posted by Kyle

Jeff,

Under #1.. Hardwood grading rounds up as well for width the thought process being that some will be over and some will be under average over volume is the median. I have found that commercial product purchased for resell is pretty spot on and uses this methodology.

EX. 7.75 is greater than 7.5 and rounds up to 8" . 7.4 would round down to 7"

another way to do it with a calculator is by inches..
2" x 8" x 8' or

2" x 8" x 96" = 1536 inches then divide by 144 = 10.67 bf

The wholesalers and high volume guys measure this way. We small sawmill guys are generous.

Under #3

A board that say is 12" wide and 1' thick and 9 feet long may have a defect (knot or hole) on an edge and still be considered FAS due to the cutting units.

I always advertise as SELECT due to the stringent FAS criteria.

Also Walnut and cherry sap are NOT considered defects.

Determination of Grade is not easy and the graders go to school for certification for the short course or whole enchilada.

A new grade that seem to be arising more often is FAS 1F (1 clear face)

Kyle I hoped you and some of the sawyers would chime in here... You make some good points... although I'm not quite done with this yet still need to do 1F1, Select, #1 and #2 grade basics. I'm trying my best to stay away from species specific grading only because the NHLA are very clear about species allowances and defect.

I inquired NHLA about certification - believe it or not they told me their is no "certification" for hardwood grading but there is for softwood. Because of structural safety concerns.

Your right on target when you say "The wholesalers and high volume guys measure this way. We small sawmill guys are generous." Us small guys need to keep things simple cause we do most everything ourself.

I'm not an "official" grader, grading was always kind of a mystery to me. Now that I have figured out the basics. It's no longer a mystery - actually it's very definable and mathematical driven. There's really no smoke or mirrors only some simple to understand math formulas.

I ordered a grade stick to grade dry lumber, I'm going to figure out how to use it.

Thanks

[jeff...]

Originally Posted by Grgramps

Jeff, I think we all benefit by understanding how board feet are calculated. (It's not like buying 5 lbs of potatoes.)

Is there a difference when calculating board feet of green wood and wood that has been dried? The reason for asking is because when I bought from Gennetts in Asheville they made the calculation to account for the shrinkage of the kiln dried lumber.

I haven't experienced this elsewhere so I wonder if this is just their policy? It has probably been a couple of years since buying from them after finding other lumber sellers did not follow that method. I can't say how they presently calculate.

Roy

Roy - NHLA Rule #4 states:

"4. Lumber shall be inspected and measured as the inspector finds it,
of full length, width and thickness. No allowance shall be made
for the purpose of raising the grade, except that in rough stock,
wane, and other defects which can be removed by surfacing to
standard rough thickness shall not be considered. Nothing herein
shall be construed as prohibiting the shipper from improving the
grade or appearance of the lumber at time of or prior to shipment.
The surface grade as determined by the cutting yield shall first be
established by the inspector, after which the thickness shall be
determined. Thickness does not determine grade.
After grade and thickness have been determined, special features,
such as the amount of forty-five degree radial grain for
classification as quarter sawn lumber and the amount of figure as
specified for figured woods and some quartered woods, shall be
considered.

see (page 7 rule 5). ---> http://www.natlhardwood.org/pdf/2007_Rules.pdf

Also see page 7 Rule 8
8. Lumber should be properlymanufactured of good, averagewidth
and lengths. It should be edged and trimmed carefully to produce
the best possible appearancewhile conserving the usable product
of the log. Shipments of rough lumberwill admit 25%of surfaced
lumber when it is of the specified rough thickness. Contracts for
green lumber should specify dimensions required to provide for
shrinkage in drying.

Also see Standard Kiln Dried Rule and Kiln Drying of Hardwood Lumber page 59

Thanks

[Turtlewood]

So is it fair to say that the prices Wall Lumber and The Hardwood Store list on the webpage without grading are "select" as well and not FAS?

I always kinda wondered about that, as they don't say on the pricing page.

-Kevin

[Kyle]

"I inquired NHLA about certification - believe it or not they told me their is no "certification" for hardwood grading but there is for softwood. Because of structural safety concerns."

http://www.natlhardwood.org/school.asp?userid=
http://www.natlhardwood.org/school-tuition.asp?userid=
thats the 14 week course in memphis..

there is also a short course..(3-4 days) depending upon where its taught..lost in VA.
http://www.natlhardwood.org/events.asp

There is a short course being taught in Raleigh in May
Event Details : 3-Day Lumber Grading Short Course

Event Date: May 13, 2008 to May 15, 2008
Time: 8:00 a.m.
Place: Raleigh, NC

This course is designed for anyone wanting to become familiar with NHLA Lumber Grading Rules. It provides yardmen, sawyers, edgermen, sales and office staff with management personnel with an introduction to lumber inspection. Students should bring a notebook and grading stick if they have one.

Registration fees:

Location:

North Carolina State University
Raleigh, NC

Contact: Patti Woodbury

Phone: 919-515-5637
Fax: 919-515-8739

Click here to download printable registration form

Instructors: Joe Denig/Mark Horne

» Contact patti_woodbury@ncsu.edu