Before you line up at the cash register in a building-materials store, you might want to ask yourself: Is that 8-foot, 2×4 board you’re about to buy actually 8 feet long and really 1.5 inches thick by 3.5 inches wide?*
State and local inspectors are responsible for ensuring compliance, but they have no agreed-upon set of testing procedures for softwood lumber, such as pine. It’s not as easy as it might seem. For example, moisture content can make a large difference in a board’s dimensions, as can density, species, and even grain orientation. In the absence of specified guidelines, it’s hard to evaluate errors or compare findings, and impossible to cite a recognized measurement standard when, for example, someone lodges a complaint about incorrectly sized lumber.
That’s why the National Institute of Standards and Technology’s Office of Weights and Measures, in cooperation with the industry-based American Lumber Standards Committee and CDFA’s Division of Measurement Standards, has developed a detailed set of proposed softwood testing procedures for submission to the National Conference on Weights and Measures, which sets the consensus standards for all states to use.
The current version gives specific practical specifications for nearly all aspects of softwood inspection, including the kinds of calipers (for thickness and width) and steel tape (for length), the minimum quality and method of deployment for wood moisture meters, dimensional correction factors for moisture content (e.g., 1% shrinkage for each 4% change in moisture content) in different species, and many other factors.
For lumber inspectors, that ought to nail it down.
**Reference: Making Sure that Lumber Measures Up
Note – Establishing standards and verifying the dimensions of lumber is one of the many ways the Department of Food and Agriculture’s Division of Measurement Standards protects consumers and competing retailers who operate on very tight profit margins.
The Division works closely with county sealers of weights and measures who, under the supervision and direction of the Secretary of Food and Agriculture, carry out the vast majority of weights and measures enforcement activities at the local level.