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Standards for calculating rough sawn lumber footage?

Started by Dave Shepard, December 07, 2014, 08:48:01 PM

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Dave Shepard

For the most part, I sell 1" or 1 1/4" pine boards, or timber framing timbers. I simply do the old LxWxD/12 routine to come up with the board footage as the wood is used in it's rough form. I want to start sawing and drying some hardwoods, as well as some pine for other woodworking uses, and I'm running into the quarter system, and I have a few questions about how to calculate the board footage of different products.

I sort of understand the quarter system as far as the thickness goes. A 1 1/8" thick board would be considered four quarters, or essentially 1" thick for measuring purposes, correct? That part seems straightforward for hardwoods, but in pine I'm not so sure how to approach it. If I sell the 1" or 1 1/4" boards for use as siding or roof decking, and the board will be used rough and full volume, then I don't have a problem using the full volume when calculating the board footage. Now, if the pine board is going to be dried and planed, then the buyer wants to buy a heavier 1" board, something like 1 1/8". That presents an issue, as now I have a 1" board that is calculated as 1" thick, and an 1 1/8" board being calculated as 1" thick. :D

How are widths dealt with when calculating volume? In the past I have always cut my pine boards in 2" increments, such as 8",10",12", etc. When sawing timbers, or if I was to grade saw hardwood logs, I would get whatever width the can would yield. In order to save time while I'm cutting timbers, I stopped edging the boards down to the even 2" widths, and just edge them to clean up. Do I measure the width as sawn, and calculate each board that way, or is there an averaging system? I hate to rip everything down to set widths, especially in better hardwoods.

I'm sure I'll have more questions as I get a better understanding of commonly used systems. I want to have a system that is commonly accepted, and easily understood.
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beenthere

There is a hardwood lumber scale stick for measuring boards. And it accounts for measuring random width boards.
They are what the NHLA lumber graders use when tallying and grading hardwood lumber.

south central Wisconsin
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Jim_Rogers

Sawing pine is one thing, sawing hardwood is another.

You'll need to understand the different ways that it is measured.

As mentioned there is a hardwood measuring stick. And you would use it to measure your lumber. Then there is the rounding up or round down method. You'll need to learn that. That way you'll be figuring by the industry standard.

I'm sure others will post the correct methods used.

Good luck with this side of saw milling.

Jim Rogers
Whatever you do, have fun doing it!
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drobertson

I believe the lumber sticks measure the surface measure for the given thickness.  the only one I have is the 4/4 stick.  The way I was instructed was to use the give and take method.  This just has to be done in a consistent manner using a tally sheet with hash marks for the given surface measure for each board.
only have a few chain saws I'm not suppose to use, but will at times, one dog Dolly, pretty good dog, just not sure what for yet,  working on getting the gardening back in order, and kinda thinking on maybe a small bbq bizz,  thinking about it,

GeneWengert-WoodDoc

Softwood lumber at the sawmill and also after planing is based on the NOMINAL size.  So, a 2x4 uses the 2" and 4" thickness and width, even though the actual size is smaller.  In fact, after planing, the size is 1.5" x 3.5".  This was decided over 50 years ago.  The footage for an individual piece is given to two decimal places.  (Example:  a 2x4x8' is 2x4x8/12 = 5.33 BF.)  Oftentimes, 2x4s, etc. are sold by the piece count and not the footage.

For hardwoods, decided over 100 years ago, the thickness is in quarter inches and the width is the actual width and the length is the last full foot.  However, for an individual piece, multiply width  in inches and fractions times length, in feet but not fractions, and divided by 12 and then round to the closest whole number.  (If the answer is right on the dividing line, like 3-1/2, the first time round up and then the next time round down.)  If you use the lumber stick mentioned, the answer of this multiplication, division and rounding is automatically given by a number on the stick...this makes life so easy.  The answer is called the surface measure, SM.  It is essential to know the SM when grading.  Finally SM is multiplied by thickness in quarter inches (under 1.00" is 4/4, as well as pieces up to 1.24", with special considerations for measurements after kiln drying to account for shrinking in thickness a little bit) to get the BF.  The hardwood rule is that the footage is to the closest whole foot.  If selling several pieces of the same thickness, add all the SM first and then multiply by the thickness.  Note that the SM is measured independently of thickness, so there is only one stick for any and all thicknesses.  (Example:  a piece 6-3/16" x 1.27" in thickness and 8'10" is 6.1875 x 8 / 12 = 4.1875 = 4 foot SM.  As the thickness is 5/4, then 4 x 5/4 is 5 BF.) (Example: a 5/4 hardwood piece that is 5.26" wide x 8' 10 is also the same 5 BF, as is a piece 6.74" wide x 8'10.  Obviously, with the wider piece, you are giving extra wood away and with the narrow piece, you are not giving as much, but the idea is that it will average out over many pieces, plus it is a lot easier to to calculate without decimals.)

The individual SM values can be recorded in a tally book with hash marks or tics using special forms when there is a lot of lumber.  Often there will be one page for each grade as well.

Certainly some folks might use fractional BF of a hardwood piece to figure the footage and cost of that piece, but it is not common practice.

Here is a picture of a stick.  If this piece of lumber was 12' long (use the 12 foot length column to the far left where you see the number 12 at the top), this would measure just under 8 feet SM, so it would be rounded to 8 SM.  For other lengths, 10' is 7 SM, 14' is 9 SM and 16' is 11 SM.



 
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

GeneWengert-WoodDoc

If using this lumber stick makes sense, three more items:

First, the reverse side has numbers for odd length lumber.

Second, the 12' column is actually a regular ruler as well.

Third, what if the lumber shown was actually 8'2".  Can you get the answer from this stick?  The answer is "Yes."  And so the next question is "What is the SM for 8' or 7' or 6' or 5' lumber in the picture?" If you know how to do this, get the answers now before reading further.

The procedure is to divide all the numbers on the 16' , 14', 12' and 10' scale in half (mentally).  The key is that with all the divided numbers that end in 1/2 (like half of nine is 4-1/2), the narrower side of the "nine" box on the stick would round down to 8 and the side closest to 10 would round up to 5.  The dividing point is the two short lines on each side of the number.  So, for the piece shown, I think that the correct answers are 5, 5, 4, and 3 for 8', 7', 6', and 5' long lumber.

But, did you know that you can purchase sticks that are marked for short lumber and so you do not need to divide in half?
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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