Net measure vs. gross measure
by Keith D. Atherholt
Kiln dried hardwood lumber is sold by the board foot, and the method used to tally the board footage can make a significant difference in the true cost. Hardwood lumber can be measured two ways: "net" measure, or "gross" measure.
NET measure means that the lumber has been tallied, or counted, after it has completed the drying process.
GROSS, or green, measure means that the lumber has been tallied before it went to the kiln, or while it was still considered "green".
It's no secret that wood shrinks as it dries, and most kilns will produce lumber with a moisture content in the 6% - 8% range. This kiln drying process causes these hardwood boards to shrink between 5% to 9% along the tangential plane (generally the width of the board), with 7% being accepted as the industry standard.
In order to accurately compare price quotes, you must know which method of measure is being used.
Consider scenario #1: A salesperson quotes you a NET measure price of $1800 per thousand board feet ($1800/m), and you order a thousand board feet (bd/ft). Your bill for the lumber should be $1800, and the quantity delivered should measure 1000 bd/ft.
Now consider scenario #2: A salesperson quotes you a GROSS measure price of $1800 per thousand board feet ($1800/m), with a shrinkage factor of 7%. You order a thousand board feet (bd/ft). If your bill lists quantity at 1000 bd/ft and the cost is $1800, then the quantity delivered should measure 930 bd/ft (1000 bd/ft minus the shrinkage factor of 7%). If the quantity delivered measures 1000 bd/ft, then the bill should be $1935.48 (the $1800/m price is adjusted to compensate for the shrinkage factor).
So how does a woodworker compare gross measure quotes to net measure quotes? The simplest way is to have all suppliers use net measure for pricing. This eliminates the need to adjust for shrinkage factors. If this isn't possible, you'll need to convert the gross measure price to a net measure price.
Many buyers make this conversion by adding the shrinkage factor to the green measure price. Increasing the green measure price by the shrinkage factor will get you close to a comparative cost, but will not give you the true comparative cost. For example: You've just been quoted a price of $1800 per thousand board feet ($1800/m), with a shrinkage factor of 7%. Adding 7% to $1800 results in a revised cost of $1926/m.
To obtain the true comparative cost, you must divide the quoted gross measure price by the inverse of the shrinkage factor. Using the figures from the example above, divide $1800 by .93 (the inverse of the 7% shrinkage factor). The result is $1935.48/m.
After you have converted and compared the pricing, and placed your order, be sure to measure and verify the quantity when the lumber is delivered. That is the final step to insure you received what you expected, shrinkage or no shrinkage.
Keith D. Atherholt is President of Lewis Lumber Products