So, what started out as a 2×4 ends up being 1 ½ inches thick x 3 ½ inches wide, and a 1×6 is actually ¾ inches thick x 5 ½ inches wide. When softwood is cut into lumber, then dried and planed it typically loses ¼ inch from each side. Softwood lumber comes from conifer trees, such as pines, redwood, Douglas-fir, and cypresses. Between kiln drying, which removes the moisture causing shrinking of the wood, and planing the surfaces, the size of a 2×4 ends up smaller than it started out. This led to lumberjacks using planes to smooth out the rough-sawn surfaces of the wood. They wanted wood that was smoother and better looking. In addition to the spike in consumption, consumers began to develop higher standards in the appearance of the wood they were purchasing. The heat used when kiln drying helps keep the wood in a consistent form, limiting warping, and removes any bugs that might still be taking up residence. This led to kiln drying the lumber in order to speed up the drying time. The process of air drying the wood was slow and not overly effective since wood is hygroscopic, meaning that the wood absorbs the moisture from the air around it. Consumers began wanting more wood, more quickly and they wanted it to be “pretty”. Wood that is air dried can still contain up to 20% of its moisture which makes it retain its original, or very close to its original 2×4 inch size, therefore referring to the lumber by its size was easy, direct and for the most part accurate… and a 2×4 was pretty much a 2×4.Īs our country’s population and the need for housing grew, the lumber industry grew as well. These planks were rough-sawn, left in their natural state after being cut into lumber, and set out to air dry. The cants were then cut into straight planks that measured 2”x4”, or 1”x4”, or whatever size was needed. Originally, when trees were cut for lumber, they were cut into cants, A cant is the largest possible chunk you can cut out of a tree. With that said, you’ll see in the article below that the method used to dry wood has the biggest impact on how much wood shrinks from the time it is cut into lumber until you find it in your local lumber store. Ultimately, the reason reason wood varies from the advertised size is due to the shrinking that occurs during the drying process. A 2×4 has been called a “2 by 4” since, well…forever. When referring to soft wood that is milled and used for building, we call it by the nominal measurement and not the actual measurement. I mean if you buy a board that says 2×4, that is what you get, a board that measures 2×4, right? No, that is not right. One would assume that a 2×4 board is just that, 2 inches by 4 inches.
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