My work for the last few months has involved close daily encounters with standardized stud lumber. The logic of these standards -- width, depth, and length -- seems baffling on its face. A 2 x 4 is actually 1-1/2" x 3-1/2". It gets even more curious as these lumber standards interface with a whole universe of other measures -- sheet goods, nail lengths, insulation batting widths, and non-structural accessories.
Now, 2 by 4 has become a colloquialism, slipping into common speech as a stand-in for wood, regardless of size or shape.
Europeans arriving in America faced a forest of epic proportions. It had been managed with fire and agriculture by Native Americans, but it had never been logged with steels tools and draft animals. An abundance of timber informed the the building choices of early settlers, who were coming from a lumber-scarce continent that had largely been logged over by the 1600s. The first buildings erected by settlers -- in Jamestown and New England -- replicated building methods from the Old Country. Timber frames, made of braced posts and beams, were mortised and tenoned together. The notching, pegging, and extreme weight of the members made slowed construction and required skilled labor.
Maya Lin, 2 x 4 Landscape.
Colonists from Northern Europe introduced the log cabin as early as the mid-1600s. This method was quicker than post-and-beam, requiring less dressing of the raw logs. It was, however, more timber-intensive, requiring a lot of labor in harvesting and drying trees. Though log cabins are lodged in the popular imagination, they were generally considered a rude form of dwelling, and were replaced with brick, stone, or timber frame once a family had time and money to spare. Timber-framing remained in use for barns for centuries, as it allowed for large interior clear spans.
In the early 1800s (ca.1810), nail production was mechanized for the first time. Thesecut nails were sliced off the end of a rectangular iron bar, then hammered to a taper. In the 1890s, wire machines were able to extrude and slice the round nails we find ubiquitous today. This innovation greatly increased the speed of production, and allowed the nails to be made of harder steel instead of soft wrought iron.
Up until the Civil War, lumber was a locally-produced commodity. Forests were everywhere, and timber was heavy and difficult to ship. There were no national standards as to sizes, and pieces were milled-to-order for builders. In the postbellum era, railroads drove down shipping costs, eastern forests were logged out, and steam-powered sawmills began to turn lumber production into a massive industrial process.
A related development, balloon framing, was developed in Chicago in the 1830s. Continuous studs, roughly 2" x 4" inches, ran 16' from the foundation sill to the eaves. Erected much as a post-and-beam house would be, the studs were put up individually instead of pre-nailed into a wall assembly and tilted up. Diagonal boards, or girts, braced the corners. Suddenly, houses could be put up frighteningly fast -- a few fellas with hammers and handsaws could get a building framed out in a week.
Balloon framing, via Michael J. O'Brien.
Balloon framing fell out of favor in the early 1900s, when platform framing was developed. This system allowed for much shorter (and more economically/fiscally efficient) studs. It also made a progressive series of flat platforms, allowing for a level surface on which to build the next level of the building. Diagonal boards covered the studs, creating a diaphragm wall system, where rigid sheathing serves as lateral shear bracing. Stud spacing began to be standardized at 16" O.C. for load-bearing 2 x 4 walls.
There is not a clear reason why this number became the standard; some say it was the length of a hammer handle, others a forearm. I think it has to do with strength of materials, as trial-and-error developed the strongest system. After World War II, plank sheathing was replaced with plywood, as wartime production of plywood aircraft and PT boats was turned to peacetime purposes. The dominant sheet size was 48" x 96", which tiles neatly onto either 12", 16", or 24" joist and stud spacing.
Platform framing, also by Mr. O'Brien.
So, this is all a roundabout way of explaining the 2 x 4. A uniquely American way of building, based on available materials, speed, efficiency, and low skill, grew up on the back of the continent's vast forests. Dozens of lumber standards were developed in the 20th century, beginning in the early twenties. The main concerns for the industry seemed to be reducing shipping costs and opening regional markets to national competition. Again, some of the origins of 2 x 4, as a name, are lost to history, but it generally refers to the green size of the blanks before kiln drying and surfacing. Boards lose about a 1/4" all around due to shrinkage while drying, and another 1/4" for surfacing. Bigger boards lose more moisture and require more surfacing the flatten them out, so a 2 x 12, for instance, is actually 1-1/2" x 11-1/4". They are then graded, in descending order: Premium/Select, #1, #2, Stud, Economy, Utility. Grades are based on straightness, knottiness, and the presence of other defects that might degrade structural integrity. The finished stick is marked with a stamp detailing grade, species, moisture content, and mill of origin.
Back when I lived in Alabama, attending the Rural Studio, I went on a field trip to a lumber mill. Turns out, surprisingly enough, that Alabama is the largest timber-producing state outside of Alaska, which explains the predominance of southern yellow pine in stud stock across the country. The whole production was fascinating. First, logs were de-barked, then sliced into blanks by a huge bandsaw that used 3-D scanning to divine the most efficient way to render the round cross-section into rectangular pieces. These blanks were then further sorted, surfaced, and dried. The heat for the kilns was generated by burning sawdust. Nothing was wasted.
I use stud lumber in a lot of my furniture projects, not for its beauty, necessarily, but because it is cheap, readily available, and in standard sizes. Every house in America may be different, but it's built from the same kit of parts, snatched off the shelf and nailed up. I like the idea of my furniture built from the same bones as my apartment, the invisible brought out of the walls and into the living room.