Cords and boards: Terms explained
Loggers, foresters, and wood mills use specialized units of measurement to describe wood in both standing trees and cut forest products. Cords, boards, MBF, bolts, and tons are a few of the more common terms. Obtaining market-suitable volumes from tapered, irregular cylinders pose geometrical and processing challenges.
Tree stems come in a variety of shapes, tapers, diameters, lengths, and other size elements. Trees are not uniform in their geometry. Forest management, genetics, soil conditions, and other factors influence the shape of a tree and its trunk. Sometimes it’s important to estimate wood volume of an entire stand of trees. Other times, it’s important to estimate a usable volume within individual standing trees or logs. Many measurements include only the wood in the trunk. Other measurements also include branches, roots, or both.
A logger manufactures “roundwood” volumes from standing trees, and then sells those products to different mills. A healthy market environment allows a logger to sell more of a tree to area mills, such as those that make veneer, lumber, pulp and paper, utility poles, heating products, and others. Having volume measurements are essential to the buying and selling of wood. For some products, weight is used.
The merchantable “bole” (stem, trunk) has been the traditional focus of measurements. Minimum diameters at dbh (diameter at 4.5 feet) are typically five inches. Hardwood (broad-leaf trees) sawtimber trees typically have at least an eleven-inch dbh and a nine-inch top diameter inside-bark (dib). Softwood (conifers) sawtimber trees typically have at least a nine-inch dbh with a dib of seven inches. Building construction has driven these specifications. Other measurements for raw wood exist with increased use of wood for non-solid wood products, such as fuelwood, composites, and chemical extraction.
A cord is a stack of small logs, called “sticks” or pulpwood, that are generally unmarketable for higher value products, although in some regions, sawtimber and veneer logs are also sold in cord units. Dimensions are a 4×4 foot face of eight-foot sticks (actually, 100 inches) with a minimum small-end diameter of 4-5 inches. Of course, a cord contains a lot of air space, variable with the diameters of the sticks. Typically, the solid wood conversion is 79 or 80 cubic feet. Note that a “face cord” is a firewood measure that usually has a 4×8 foot face but the length of cut-and-split wood can be almost anything, but often 16-24 inches. Standard firewood volumes don’t exist, so it’s more of a buyer-beware market.
A cubic foot is the volume equivalent of a block of wood 12x12x12 inches. It does not account for reductions for sawing or other processing, so it’s a measurement of all the wood inside the bark of the merchantable portion of a tree trunk. Cubic foot volume doesn’t typically include branches or roots. The U.S. Forest Service, Forest Inventory & Analysis unit uses cubic feet to help describe American forests. In most other countries, cubic meters are used as a standard measure.
A board foot is the volume equivalent of a block of wood 1x12x12 inches. The estimate of board feet in a tree or log includes reductions for saw kerf (width of a saw cut that becomes sawdust), sweep (curvy logs or trees), and tree taper. So, the volume consumed to produce twelve board feet would not fit into a cubic foot box. Stated another way, a cubic foot has about 9.8 board feet due to sawdust volume from a 1/4-inch kerf. Board foot volumes are usually expressed as “thousand board feet” or “MBF”. Different scales are used to estimate the MBF in logs versus trees. For logs, a scale stick is used on the small end of the log, inside the bark, knowing the log length. For example, a 12-inch dib log, 10-feet long, would contain about 55 board feet of lumber. For whole trees, dbh and the number of eight-foot (or sixteen-foot) logs are used.
There are three major scales, Scribner, International, and Doyle. The most common in the Lake States is the International 1/4-inch rule (1/4-inch kerf). Scribner tends to be more accurate for smaller logs and Doyle more accurate for larger logs.
Sawlogs are larger, higher quality cut products used to produce lumber. Typically, there are three quality grades. Logs of particularly high quality and desired specifications can be sold as veneer logs. Veneer is a thin ply of wood commonly used for panels and furniture exteriors.
Other logs that don’t quite meet mill requirements, are undesirable species, or have some other characteristic are called “bolts”.
Posts, piles, and utility poles are among other specialty products that can sometimes carry high monetary value. In the Lake States, high value red pine is usually used for utility poles.
Length and width of boards are described in feet and inches but the thickness is sometimes described by “quarters”, or quarter-inches. This is largely industry lingo. So, a “five-quarter” board would be five quarter-inches thick or an inch and a quarter. A 2×4 at the lumber yard isn’t the full size due to the value-added processes of planing and drying. The rough-cut board had the full dimensions.
Another peculiar term is a “cant”, which is a squared-off log, ready to be sawn into boards. Railroad ties are cants with specific dimensions and wood specifications.
Weight is sometimes used as a measurement, usually as tons or tonnes. A “ton” is more familiar, at 2000 pounds. A “tonne” (or metric tonne) is 1000 kilograms, or about 1.1 U.S. tons. Biomass is measured in tons or tonnes. Because wood density varies by species, the weights per unit volume will vary. A cord of wood will weigh about 2.3 tons, give or take a few decimal points. A thousand board feet will weigh from 2500 to 5500 pounds, green weight. Lumber or dry weight will be 15 to 50 percent lighter, depending upon the species. Wood pellets and wood chips are generally delivered in “tons”. Pulp mills often buy wood in tons, rather than cords.
It’s been said that the forest industry is so efficient that every part of a tree is used except the shadow. While lumber may be cut from the largest portion of a log, the slabs, bark, and sawdust all have markets, at least in a region with a vibrant forest economy. Pulp mills use only the “clean” wood but the bark is used to help produce the heat and power for the paper-making process.
Research continues to offer new ways to use wood, sometimes to replace non-wood products whose manufacturing consumes far more energy and other resources. Cross-laminated timber can replace steel and concrete in building construction. Car bodies, “plastic” bottles, medical supplies, clothing fibers, vehicle tires, and many other products may be made from trees in the near future through the use of innovative technologies. Wood is the most environmentally-friendly raw material, especially when considering energy and water inputs, as well as atmospheric carbon balances.
As a retired MSU Extension forester, I still enjoy providing educational programming. A collection of these newspaper articles, back to July 1997, can be viewed on the following website: http://miforestpathways.net/ForestInfo/Newspaper/0000-Index.html