Joints of Wood

Illustrations by Sirichai

Sometime after 10,000 B.C., early man got sick of living in caves and started building “houses” out of wood. This raised the problem of how to connect different pieces of wood, since trees do not, on their own, grow into the shape of split-level ranches.

So the ex-cavemen lashed sticks together with vine. The resultant structures were great, as long as you didn’t brush up against them. Around 3,000 B.C., man again tried to improve the situation by engineering the first proper wood joint.

The earliest known wood joint was a crude mortise-and-tenon, a roughly carved shaft fitting into a hole. (The exact inspiration for this joint was never documented, but it’s a safe bet the inventor wasn’t a virgin.) For millennia our toolboxes were filled with rocks, and this was the best we could do.

New tools improved our problem-solving capabilities. Around 2,100 B.C. the first bronze tools started cropping up in present-day Thailand, and by 1,800 B.C. the Indian subcontinent started cranking out iron tools. By 700 B.C. the Chinese and Koreans had them. Sometime around 476 B.C. a Chinese inventor named Gongsu Ban developed a woodcutting saw. Chinese carpenters could now cut wood with something like precision, which changed everything.

The traditional Asian wood saw, unlike its gun-handled Western variant, resembles a long, flat spatula. It is a precision tool that cuts on the pull, not the push, so it affords less power than a Western saw, but greater accuracy. Using this tool, Chinese carpenters devised an intricate system of cutting connecting elements into the wood itself. Since nails didn’t exist, these carpenters had to carve different pieces of wood to not only fit together, but to lock together, support weight without breaking and stay that way throughout the centuries.

A series of splices and dovetails was developed, some for connecting disparate structural elements (fastening crossbeams to vertical posts, for instance) and others for lengthening (combining two beams end-to-end into one long beam, without sacrificing strength). As the techniques spread throughout China, Korea and later Japan, carpenters along the way slowly improved them, resulting in fiendishly complicated splices, of an estimated several hundred types, that continue to amaze even present-day engineers.

Even more impressively, all of these joints had to be carved to fit together precisely while still compensating for the natural “give” of wood. One technique was to dry freshly-cut lumber in a kiln, sucking the natural moisture out of it. The wood was then cut and joined. The wood would subsequently reabsorb moisture from the air, causing it to expand and tightening the joint into a more or less permanent fit.

Carpenters trained in this type of joinery were, centuries before the birth of perhaps the world’s most famous carpenter, cranking out consistent and precision manufactured parts that predated the Industrial Revolution by nearly two millennia. The tolerances required to produce a precise fit that could safely bear loads for hundreds of years were down to the millimeter, in an era before millimeters were demarcated. And because the techniques were largely applied to the construction of royal buildings and temples, the joints couldn’t be merely functional; they had to be beautiful or, like the best technology, invisible. The profession of temple-building carpenter was a true combination of artist, artisan and engineer, something akin to today’s industrial designer, in the purest Raymond Loewy sense of the term.

Mankind evolves largely by using self-created tools to alter things from crude to refined. This quality can be seen to have reached something close to perfection in Asian wood joinery. But today, in Asia as elsewhere, wood is no longer the building material of choice, and a CNC milling machine can tirelessly accomplish in seconds what it used to take someone 15 to 30 years to master. Mass-produced metal fasteners and wood glue have nearly eliminated traditional wood joinery. Carpenters skilled in the techniques mentioned here have dwindled to a handful, largely employed for the restoration of ancient temples.

The Yakushiji Temple in Nara, Japan is currently undergoing a long-term restoration, providing some of Japan’s fifty remaining master temple carpenters with a project they can sink their sawteeth into. Also located in Nara is the the Horyuji Temple, which contains a set of the oldest surviving wooden structures in the world. The four buildings, including a five-story pagoda, have stood for some 14 centuries. Not bad for a building with no nails.