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Japanese Conventional Wood Construction Methods in the Modern Era
A consideration of major texts

By Kentaro Kobayashi

The codification of the “Japanese Conventional Wood Construction” methodology

The phrase “conventional structural methods” has been broadly understood to mean residences constructed largely from wood. Japanese construction dictionaries define “conventional construction methods” as, “construction methods continued in generally the same manner as in the past.” However, since traditional construction methods depend on traditional manufacturing systems, differentiation between “traditional” and “conventional” becomes necessary.

That is, the definition of what is “conventional” must include relatively new techniques that have come into common use. However, the formal codification of “conventional Japanese construction” was adopted during the postwar reconstruction period (1950), when the entire system for construction financing and regulation (the Government Housing Loan Corporation and the Building Standards Act) was being restructured. At that time, “conventional Japanese construction” was broadly defined as, “construction methods which are not modern”, or even more harshly, “construction methods which are not appropriate for the housing of the future.”

“Modern construction methods” were generally defined as panel construction, whereby a light framework is constructed with mechanical connections, and various kinds of infill panels are attached to it. This method now accounts for the overwhelming majority of Japanese residential construction. Unfortunately, many of the building parts were fabricated of petrochemical materials or other substances which are now known to be hazardous to human health, as well as of poor durability. To compensate for these problems, efforts have been made to improve the safety and durability of the infill panels themselves. One approach to solving these issues has been to return to the construction of dwellings using only natural materials. However, “all-natural” construction methods require a much higher level of technical mastery, in large part because natural, organic materials are not standardizable. Because of the contempt in which these non-standardized methods were held during the post-war years, much technical knowledge for Japanese indigenous wood structural methods was lost.

We here encounter the theme: “technical continuity”.

In general, architecture and construction texts tend to separate construction materials and methods into easily definable categories, such as, pre- and post-WWII, Meiji-era, or Edo-period. It is true that technology has changed (progressed) according to the demands of the current era. However, the progress of technology should always occur based on continuity with previous technology, just as technical skills are not the closed province of individual craftsmen. For example, the traditional craft of carpentry has been demonstrably improved by research and engineering in wood construction technology, but its base is still evident. Thus, strict categorization of any given technique is not always easy or possible.

When considering this “technical continuity”, the emergence of new technologies must be dealt with. In this context, “Conventional Japanese Construction” was exposed to a massive influx of new technology as the country was opened in the Meiji Period. Here, we consider the formation process of the “conventional Japanese wooden structural methodology” after the Meiji Revolution, and more specifically its development since the end of WWII.

Changes in Technical Construction Manuals
Changes in “conventional methods of structure” from the period of the Meiji Reforms until the beginning of WWII

In 1887, the Meiji government passed a law requiring all printed materials to be submitted to the government for approval before publication. This is a convenient basis for research, since the National Diet Library has continuously maintained this source material since that time.

A technical document entitled, “Conventional Construction Methods”(※1) became the basis for the technical training of construction professionals, and various revisions were published until the beginning of WWII. The text was a major reform over the apprenticeship method of construction education which was the normal practice through the end of the Edo period. In keeping with other Meiji-era reforms, it promoted the abolition of the “learn-by-doing” method of passing on knowledge, replacing it with the ideas of “education” and “study”. That is, the text was an attempt to disseminate wood building techniques in written form.

From left: “Conventional Wood Construction” (“Futsū Mokkō-jutsu”; Dai Nihon Tosho, 1899), “Structural Improvements for Japanese Homes” (“Kairyō Nihon Kaoku Kōzō”; Dai Nihon Kōgyō Gakkai, 1919), “Structure in Western Architecture” (“Seiyō Kenchiku Kōzō”; Chūō Kōgaku-kai, 1930)
From left: “Conventional Wood Construction” (“Futsū Mokkō-jutsu”; Dai Nihon Tosho, 1899), “Structural Improvements for Japanese Homes” (“Kairyō Nihon Kaoku Kōzō”; Dai Nihon Kōgyō Gakkai, 1919), “Structure in Western Architecture” (“Seiyō Kenchiku Kōzō”; Chūō Kōgaku-kai, 1930).

 Who wrote, or could write these texts? The authors were master carpenters and master builders who were practicing “ordinary structural methods”.(※2) In the preface of the first of these texts, the authors write, “This is a hereditary trade known as “Kiku” (Right Angle, or Carpenter’s Square).” What is “kiku”? At the time of first publication, a common description of traditional wood building methods was “Kiku-jyutsu” or the “Art of the Right Angle”. The Dictionary of Construction defines the Art of the Right Angle as, “Graphic methods of producing images of structure, joints, roof forms, and fittings for wooden buildings.”

A book, “The Art of the Right Angle” was published during the Edo period as an aid to apprentices, and was also revised and published until the 1920s (Taisho period). At that time, the publisher (Suhara-ya Shoten) had close ties to the Edo Shogunate, but this publishing house survived through the Meiji and Taisho periods, printing various books about construction technology. These texts provide a level of continuity in construction documentation.

Illustrations and cover photo from “Kaoku kenchiku tsubo-kyoku sokusei zukai” (“Measurement in Quick Residential Architecture Illustration”, Tanaka Sō Sakae-dō 1914).
Illustrations and cover photo from “Kaoku kenchiku tsubo-kyoku sokusei zukai” (“Measurement in Quick Residential Architecture Illustration”, Tanaka Sō Sakae-dō 1914).

In contrast to the technical construction training documents written in the Meiji and Taisho periods, pre-WWII texts were written by mid-level government bureaucrats and engineers, the texts tended to be dominated by “new” technology—technology imported from the west. Being engineers rather than researchers, their focus was on novelty and practicality. The language they used reinforced this bias, labeling wooden technology as 「和」(wa: Japanese), and imported construction technology as 「洋」, (yo: foreign (western)), in the same way as clothing and food was categorized as “Japanese” or “foreign” (wa-shoku, wa-fuku; yo-shoku, yo-fuku). In these texts, imported Western technology is given precedence, while indigenous Japanese building techniques are generally treated separately. This pattern in texts continued through to the 1940s, treating “Japanese” and “Western” technology as mutually exclusive.

In the following illustration, the Japanese-style construction is demonstrated in a “sashigamoi (three-way) joint between beam (hari), cross-beam (nuki), and column (hashira) of a storage building. Western-style construction is demonstrated with a corner “truss” (triangle bracing of the corner) in a stud wall with mechanical connections. As is seen in this example, the authors present technical challenges and practical interpretations for the most common construction forms.

Left: Illustration from Hiyojiro Saito’s “Nihon kaoku kōzō” (“Japanese House Structure”, Nobutomo-dō, 1904).Right: Illustration from Michimatsu Kitaatae and Masae Kase’s “Wayō mokuzō kaoku kōzō zukai” (“Japanese Wooden House Structure, Illustrated”, Suhara-ya shoten 1918)
Left: Illustration from Hiyojiro Saito’s “Nihon kaoku kōzō” (“Japanese House Structure”, Nobutomo-dō, 1904). Right: Illustration from Michimatsu Kitaatae and Masae Kase’s “Wayō mokuzō kaoku kōzō zukai” (“Japanese Wooden House Structure, Illustrated”, Suhara-ya shoten 1918).

The illustration on the left details a wooden, three-directional joint (sashigamoi). This joint is used to typify “Japanese Style” construction methods, and is given as an example of its structural deficits, as the joint is described as significantly weakening the column while at the same time concentrating force there. This argument was the basis for the academic preference for the use of “foreign” construction technology, which can be seen in most construction texts and technical documents published before WWII. However, it is not clear from current research that this form is in fact weaker than a similar form made with mechanical fasteners.

The right-hand illustration details an angled joint into a foundation. (Hiuchi: a horizontal angle approached by a diagonal member.)

This can not be considered a 100% “foreign style” joint, but it shows both ends fixed using hardware connecters. Moreover, in evaluating this “western” joint, this technical article describes the rigidity of the resulting joint to be equivalent to the traditional wooden “kusabi” joint. This article can be viewed as an advocate for the compatibility of wood members with hardware joints (technical continuity).

Zenzou Yoshida, “Structural Improvements for Japanese Homes” (“Kairyō Nihon Kaoku Kōzō”; Dai Nihon Kōgyō Gakkai, 1919).
Zenzou Yoshida, “Structural Improvements for Japanese Homes” (“Kairyō Nihon Kaoku Kōzō”; Dai Nihon Kōgyō Gakkai, 1919).

 This diagram shows a “foreign style” roof truss. However, as is clear from the diagram, the eaves are deep, and the roof slopes up at the corners in the Japanese style, for which the Japanese traditional “hanegi” method of construction is used. In addition, the construction of gable (kiridzuma) and hip (yosemune) roofs are described. This procedure is technically difficult and complicated because the slanted shape is gathering the forces in a 5-way joint. The book describes and details and names various new complex column forms, such as the “pestle” column, the “turnip” column, the “pumpkin” column, etc.

Texts published in the period between the end of the Meiji era and WWII can be divided into ideologically conflicting “conventional technology” and “new technology” categories, however, they are very valuable when considering current (21st century) methods of wooden construction.

Development of “conventional construction methods” in the future

As we have seen, the history of Japanese wooden construction technology from the 1870s to the 1940s (Meiji to Showa periods) was heavily influenced by imported European and American “new technology”. Things that were considered useful were imported wholesale, while things not considered useful were rejected.

This influence was greatly strengthened by laws and regulations promoting standardization, enacted after the end of the war. Even before the enactment of the “Building Standards Act” (1950), the 1919 “Urban Construction Act” was intended to improve fire and earthquake safety in urban areas. However, as its name indicated, the 1919 law was restricted to urban areas, while the 1950 Building Standards Act covered all buildings, including zoning regulations. These regulations, written by technical bureaucrats, attempted to standardize wood construction technology in order to improve productivity, promoting the creation of large homebuilding companies. Regarding standardization, we can say that they were largely successful.

Since the moniker “Japanese conventional construction” has come to mean, “construction methods of the past”, it seems reasonable to use a different term when describing wood construction based on Japanese traditional methods, such as “native Japanese construction methods”. In addition, laws requiring standardization have recently been relaxed. Building long-lasting homes using this “native Japanese construction” technology means connecting with the benefits of traditional wood construction in a way that maintains a technological continuity while avoiding a stagnant repetition of old methods. It is essential that we do this, to maintain Japanese traditions in a living way.

Notes:
(※1).The primary documents mentioned in this paper were selected from the 88 manuscripts of the “Construction Techniques Manuscripts Published Between 1890-1945” collection in the National Diet Library of Japan. From the original 88, 20 manuscripts were selected as particularly representative of construction technique of the time. This collection in the National Diet Library is the most complete of its kind, since publishers at the time were required to provide copies of such reports to the Department of the Interior. Research concerning “Kiku-jutsu” (the Art of the Square) was greatly aided by the bibliographic research of Mr. Norihito Nakatani.
(※2).The majority of the manuscripts examined here were written by faculty of educational institutions. Technical education at the time assumed that instruction would be based on the physical construction of a real house, so teachers were selected who had both practical work experience and a progressive view of technology. This paper is primarily concerned with an examination of construction texts. For more information on architectural education at the time, the reader is referred to previous studies by Mr. Keiichi Shimizu.

This paper was originally published under the title, “Technical books relating to the emergence of modern Japanese wooden architecture; A bibliographic study,” Proceedings of the Architectural Institute of Japan (Vol. 588, pp 181-186; February 2005).

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