Why Japanese Joinery is Designed to be Disassembled

by Karl Bareis (adapted from The Wooden Post, vol 12, September 2018).

The following article is inspired by the Wooden Post’s ongoing series, exploring the resilience of traditional Japanese structures. The question of what techniques were employed early-on to allow the evolution and systematic improvements to the joinery which eventually would resist jolts and winds, for tens of centuries. 

A Brief Historical Overview

The history of joinery in Japan has several converging roots. Ancient Jomon architecture has its roots in cultures from Yunnan China dating back 17,000 years. They used stone tools and built partially underground, burying the posts up to two meters in the soil. The most ancient Shinto style, used at Ise Jingu, also utilizes many of the same buried-post techniques. Elements of the Jomon prehistoric storehouse architecture still survive in the methods of modern carpenters currently used in rebuilding sacred Shinto shrines.

Recycling Materials A Key to the Past

The oldest surviving wooden building in the world is situated in a dry sandy courtyard, surrounded by other ancient buildings but none within 200 years as old as the pagoda. These ancient buildings at Horyuji also had another carpentry tradition unique to Japan which had survived centuries with little change. What better way to keep your builders well-trained than to force them to rebuild the capital at each change of the Throne. Other factors including physical pollution and overcrowding reinforced the need to move to open ground and map out another Capital — one that reflected the ever-changing rotation of power within the ruling class. The princely families jockeyed for position opposite the palace grounds, so mansions were carefully dismantled in the doomed capital and moved to the new estate, which was determined based on hierarchy within the court.

Table from: A historic account of Toshio-dai-ji buddha hall, in Nara
(from local temple documents translated in 1998. Spelled “Toshodai-ji” in this article.)

Table - Why Japanese Joinery is Designed to be DisassembledDuring the seventh century no less than five capitals are described in the Nihongi Chronicles. In 2005 during periodic repairs of Toshodai-ji Temple in Nara, archaeologists confirmed that parts of the current Buddha Hall (see image and chart next page) had once been the main Honden ceremonial hall of the Imperial court. The structure showed wear in areas that revealed that indeed even before the temple structure was erected in 747 AD, it had been likely used in yet a different building in the Naniwa capital near present day Osaka. Many standing buildings from the early Nara Period actually contain individual beams from yet earlier structures, deconstructed in a defunct capital many miles away and floated in rivers or carried overland to be recycled into “modern” buildings which reflected slight changes to roof lines and esthetics, as well as observations of structural weaknesses observed during the careful deconstruction process.

Why Japanese Joinery is Designed to be Disassembled

Note: Every repair required that the roof frame be stripped off and exposed to make repairs. Of the seven listed repairs only three were earthquake related.
Earthquake repairs were rapid assessment and repairs as needed, major rebuilding as in 1323, were major deconstruction events including replacement and redesign and retrofitting new roof lines to match the evolution of temple structural design especially related to roof overhangs and cantilevered bracket systems.

Standing at Horyuji Temple, miles from the eventual “new” capital in Nara, it’s easy to see stylistically how much the architecture had changed from 607 AD. In just under 150 years, the buildings’ architectural and structural systems had evolved massively. By the time of the Nara Capital, carpenters had evolved a system of joinery that allowed for regional workshops to make up modular brackets, based on a commonly accepted measuring tool. The Imperial tax collectors had instituted barter taxation based on cubic volumes of wood products as early as the sixth century, so when Nara temple carpenters decided on a single official shaku measurement, (roughly one foot), the government placed the Ivory shaku measuring tool in its official Shoso-in repository, and thereby instituted universal measurement accuracy so critical to the government that measurements and proportions were legislated into law. During this same 150 years there were two magnitude 8+ seismic events centered on the capitals. Evidence points to fires following the earthquakes, and marked differences in “before and after” architecture. Buildings that burned were quickly replaced, but those that were severely damaged in the earthquakes were never rebuilt. However, evidence from the Toshodai-ji research suggests that surviving beams were salvaged and joinery was revised. Modern engineers test systems to failure, in order to revise their calculations and improve the overall strength of systems. This process is too expensive to be used with entire structures. It’s reasonable to think of carpenters in the seventh century being keenly interested in what could possibly have shaken their post and beam structures to the point of failure. Several modern structural evaluations have shown that the evolution of architecture in Japan has been driven by the natural test-to-failure mode of the earthquake-prone country.

The drive to create durable “monumental” architecture that could be disassembled and rebuilt was the largest factor in creating uniformity of building practices during the ancient era. At first, because a very large proportion of Japan’s islands are covered with coniferous forests, she was able to continue felling ancient forests and using construction projects to further stimulate the economy. Even so the massive rebuilding of cities coupled with recurring natural disasters meant that the materials had to be transported further and further as time went by. One of the dendrological surveys of Nara temples shows that by the midseventh century large posts and beams were coming from more than one month’s journey to the east. This expensive process of moving timbers from steep mountains helped to stimulate the next great innovation in monument building. Areas with deep forest canyons had local woodsmen and carpenters, and soon they were being asked to fabricate parts rather than raw logs. In this early period Buddhist teachers wanted to create several temples in far-flung provinces. The temples were all designed by Nara miya-daiku temple builders, with thousands of individual brackets carved to fit the new shaku-based templates. This allowed a relatively small cadre of skilled carpenters to erect the monumental Kokubunji temples, from Kokura in the far southwest to Kanto plains in the east. Our exploration of the importance of understanding Japanese architecture can be best understood by looking both at the rapid expansion of techniques and the willingness of carpenters to monitor the results of their work over time. Deconstruction of monumental architecture undoubtedly had a profound influence on techniques, as well as organization, logistics and uniformity of final product. We see by the rapid expansion of the Buddhist culture that it played a key role in developing skilled craftsmanship throughout Japan.

Why Japanese Joinery is Designed to be DisassembledMany other factors also drove the evolution of architecture. The abundance of timbers created a sustainable atmosphere for regional trading hubs to source materials for large-scale undertakings. Taxation and government policy also were extremely important factors in building heights, esthetic design, and access to materials. Many crafts and skills within Japanese woodworking community developed because of the interlinked economy; skills could be traded. These skills were used as barter by regional warlords for more than one thousand years after the Nara period.

This article is meant to emphasize the importance of monumental architecture in developing the ancient technologies which we now think of as both engineering and architecture together. In the modern world we’ve come to consider engineering requirements as the only scientific method to build. Japan’s adherence to making each structural element out of the most durable wood results in the knowledge of each generation accumulated to create better systems. Flexible architecture which can move freely and survive disasters is the outcome of their efforts. Perhaps Kezurou-kai, with our focus on the tools and shavings, could also explore the roots of the durability of the structures to help us become part of a more sustainable future. Most of us will not build monumental architecture, but we can understand that the same criteria in the joinery found in the ancient temples is part of the tradition that we are trying to preserve.