[Amazing Masonry Techniques of Omi]

When strolling around the Sakamoto area of Hieizan in Shiga Prefecture, old stone walls can be seen everywhere. The characteristic of stonewalls in this area is that they are piled up with stones of different shapes and sizes. I wondered, as a layman, if they would collapse, but in fact, this masonry technique is a crystallization of wisdom, boasting a strength superior to concrete blocks, and is resistant to earthquakes and has excellent drainage.

A group of masons called “Ano-shu” has been active in this neighborhood for a long time. Although the detailed history of the Ano-shu is not known, it is said that they were originally a group of people from overseas with expertise and skills. It is known that the masonry techniques used in the Ano-shu mounds have characteristics similar to those used by the Ano-shu in later periods.

Ano-shu is a master of Nozura-zumi, a style of piling in which quarried natural stones are combined without processing. Anotazurazumi is called “Ano-shu zumi” in particular. However, there are no fixed rules for this method of piling. It is said that craftsmen listen to the stones and pile the stones in the right place. There are no written records of the construction method, and everything has been passed down orally for hundreds of years. This is not because it is a secret, but rather because it is necessary to stack the stones while taking into consideration various factors such as the stone face, the grain of the stone (the direction in which the stone tends to break), the height of the stone, the weathering of the stone, and so on. It can only be learned through experience, and it cannot be taught in written form. It is a technique similar to Zen training, in that the stones will eventually tell you where they should be placed if you continue to work with them for a long time.

The greatness of Ano-shu zumi became widely known during the Warring States period (1467-1568). Nobunaga was so impressed that he asked Ano-shu to build the stone walls of Azuchi Castle, and many famous feudal lords called on Ano-shu to build their castles. Many of the stonewalls of castles that remain as “famous castles,” such as Takeda Castle in Hyogo Prefecture, were built by them.

Thus, Ano-shu zumi has historically been known for its robustness, but how does it fare by today's standards? Recently, in order to measure its strength, an experiment was conducted in which Ano-shu zumi and concrete block retaining walls were placed side by side and as much as 250 tons (the equivalent of one jumbo jet) of heavy pressure was applied to each. The concrete block wall could not withstand the pressure of 200 tons and cracked, while the Ano-shu zumi wall continued to support the weight until the end, even though it was partially displaced by up to 13 centimeters. In a subsequent experiment conducted by Kyoto University, it was also proven to withstand shaking on the same scale as the Great Hanshin-Awaji Earthquake. Although at first glance the Ano-shu zumi looks disjointed, the secret of its flexibility and strength lies in the fact that the stones are placed where they should be and that they are not fixed in a uniform manner.

From the Edo period to the present day, the demand for castle construction disappeared, and the Ano-shu also gradually changed their livelihood. Today, Awata Construction in Sakamoto is the only company that has inherited the techniques of the Ano-shu. Awata Construction not only plays an active role in restoring temples, shrines, and castles throughout Japan, but also actively holds workshops and other events to pass on its techniques and train younger workers. The company is also expanding its activities overseas, such as piling stones for the exterior of the Dallas Rolex Tower (Texas), a Rolex customer center designed by Kengo Kuma.

Unfortunately, despite such strength and durability, current Japanese law does not allow the use of this technique for new construction above a certain size. It has long been pointed out that the use of concrete to harden mountain surfaces and rivers cuts off the circulation of water in the soil and destroys ecosystems, and one can only dream of a time when techniques more in line with nature, such as Ano-shu zumi, would be more commonly adopted.

Sakamoto has a quiet and beautiful townscape with signs of the old days. It is surprisingly close to our Sanjo showroom, less than an hour by train. We hope you will take the time to visit. We also recommend the handmade soba noodles at the long-established soba noodle shop “Honke Tsurukisoba.”

Sanjo Showroom
https://www.shokunin.com/en/showroom/sanjo.html
Honke Tsurukisoba
https://www.tsurukisoba.com/

References
https://www.anoushu.com/technique
https://www.kensetsunews.com/web-kan/693661