Yamamoto Lock Machine (formerly Yamamoto Iron Works) First

Yamamoto Rock Machine (Former Yamamoto Ironworks) Factory No. 1

Seventy-eight meters of timber, under one continuous roof. That is the working shop floor of Factory No. 1, built in 1934 in the small mountain town of Tojo, in the northeastern corner of Hiroshima Prefecture. It was never converted into a museum. Machines are still assembled beneath its wooden trusses, and the rock drills that leave the building are shipped to tunnel headings and quarries far beyond Japan.

The company that owns it, Yamamoto Rock Machine Co., Ltd., began in February 1915 as a one-man foundry run by Yamamoto Shuichi. Its first products were cast ironware for households. From there the shop moved into repairing and building stationary engines and sawmill machinery, the kind of work a country town needed.

What changed its direction was water. In the late Taisho and early Showa years, dam and power station construction on the Taishakugawa and Nariwagawa rivers brought crews and imported rock drills into these mountains. The Tojo workshop took on the repairs and the spare parts, and out of that came a decision to build the drills itself rather than import them. Company records note that a German engineer was invited to teach heat treatment, the process that governs how long a drill steel survives against rock. The business was incorporated as Yamamoto Ironworks Co., Ltd. in February 1939, and adopted its present name in 1996.

Factory No. 1 belongs to the moment just before incorporation, when the drills had found their market and the sheds behind the old town street were no longer big enough.

Why It Was Registered

The building carries the status of Registered Tangible Cultural Property (Toroku Yukei Bunkazai), entered in the national register on 25 February 2016 as No. 34-0156, in the 83rd round of registrations. Seven other buildings on and around the company's land were registered on the same day.

This is a different instrument from designation as an Important Cultural Property or National Treasure, and the difference matters here. Registration was introduced by the 1996 revision of the Law for the Protection of Cultural Properties to cover the enormous stock of modern buildings that fall outside the older designation system: factories, schools, bridges, shops, houses from the Meiji period onward. Owners notify the government before making significant alterations rather than seeking permission, and they keep using the building. For a plant that has to accommodate new machinery, that flexibility is the reason the shop is still a shop.

The registration criterion applied was that the building contributes to the historic landscape of the country. The Agency for Cultural Affairs record describes Factory No. 1 as the central timber structure of the complex and credits it with a functional beauty arising from the efficient working space it achieves. That phrasing is worth taking seriously: nothing about the building is decorative. Its proportions come from the twin problems of moving heavy work along a long floor and getting daylight into the middle of it.

What to Look For

The section is the thing to understand first. Rather than spanning the full width in one go, the builders divided the cross section into three bays and raised the central one above its neighbors. The step in the roofline created by that lift is filled with glazing, so light falls into the middle of the floor from above instead of dying halfway in from the side walls.

On top of the raised center sits a monitor roof, called koshi-yane in Japanese: a low, narrow structure running along the ridge with openings in its sides. It vents the heat and fumes that a forge and a machine shop generate, and it adds one more band of daylight. Look along the ridge from the street and the long shadow line of the monitor is the first thing that reads.

The recorded structure is single story, timber framed, with an iron sheet roof and a building area of 1,421 square meters. Visitors admitted on the occasional open days have reported that the framing, trusses included, is entirely wood, with chestnut used for the posts. The 1938 alteration recorded alongside the 1934 completion date accounts for part of the present length.

Standing outside on the street, the building reads as a long low bar of dark wall and pale roof, unremarkable until you register how far it runs. Inside, on the rare days when the doors are open to visitors, the effect reverses. The trusses repeat down the length of the shop and the raised center pulls the eye toward the far wall, and the geometry that looked plain from the road turns out to be the whole argument of the building.

The plant is private property and a functioning workplace. There are no regular opening hours, no ticket office, and no walk-in access. Preservation volunteers working with the company have held occasional open days, in some years timed to the town's Otoori festival in early November, when the factory interiors and the former company dormitories have been shown to visitors for a small fee. These have not been annual fixtures, so anyone hoping to get inside should contact the Shobara tourist association or the company in advance rather than turning up. From the public road the exteriors of the factory group can be seen without entering the site.