Koyanagi Sake Brewery Koji Room

A koji room with one brick face

Koyanagi Sake Brewery Koji Room (小柳酒造麹室, Koyanagi Shuzō Kōjishitsu) is a single-storey timber building of 1928 at 903-1 Ogicho, Ogi City, Saga Prefecture, listed as a Registered Tangible Cultural Property on 14 February 2002.

It stands in the north-west corner of the site. The building runs 11 metres along the ridge and 6.5 metres across, with a footprint of 67 square metres. The roof is Sangawara-buki pantile on an east-west ridge in Kirizuma-zukuri gabled form. The walls are boarded vertically, except that the entrance gable is built up in English bond English bond brick as far as the beam.

A koji room is where steamed rice is inoculated with koji mould. Temperature and humidity have to be held nearly constant, which makes it the most tightly controlled space in the whole brewing process.

One masonry wall set into a timber box

What catches the eye on Koyanagi Sake Brewery Koji Room is the division of materials. Three walls are vertical timber boarding; only the gable with the door in it is brick, and brick all the way up to the beam. The Agency for Cultural Affairs calls the construction distinctive.

The reason lies in what the room does. A koji room is kept hot and damp, so it needs a layer between itself and the outside air. Packing a timber wall with earth or rice husk is the usual answer, but the gable where people come and go loses heat every time the door opens and takes the most wear. Building that one wall as solid masonry buys both thermal mass and durability. The bond is the same English bond used for the chimney on this site, which tells us that bricklayers were on the job during the 1928 works.

The ridge runs east to west. The principal buildings of the production yard all run north to south, and Koyanagi Sake Brewery Koji Room is the exception, turned to suit its position in the north-west corner. The Muromae next to it follows the same east-west line.

At 11 by 6.5 metres and 67 square metres the room is small for a workshop, but koji is needed only in small quantity relative to the mash, so this is sufficient.

A facility a brewery cannot do without

The listing criterion is contribution to the historic landscape of the nation, and the registration number is 41-0037. The Agency for Cultural Affairs describes Koyanagi Sake Brewery Koji Room as a facility that a sake brewery cannot do without.

Much of the quality of sake is decided by the koji. Mould grown on steamed rice produces enzymes that convert the starch of the grain into sugar, and without that step the yeast has nothing to ferment. That is why the koji room is the most carefully tended space in any brewery, and why so many breweries gave it a building of its own.

It was built in 1928, within the improvement works begun in 1926, in the same year as the Showa West and East Storehouses, the kettle room, the bottling house, the Muromae and the pump house. In the order of the process the koji room receives rice steamed in the kettle room, and from here the work moves on to the yeast starter and the main mash.

In the north-west corner the koji room and the Muromae to its east form a single grouping. The Muromae is roofed from the east gable of the koji room across to the west wall of the Showa West Storehouse, making a working space in front of the room, and the two were plainly planned as one operation.

The thing to look at is the brick gable at the entrance. Masonry rises to the underside of the beam and timber takes over above it. Following the joints, where stretchers and headers change places course by course, shows the rule the bricklayer was working to.

Visiting

The interior of Koyanagi Sake Brewery Koji Room is closed. A room in which mould is cultivated is subject to hygiene control and is not a space built for visitors.

The face worth seeing is the entrance gable. The line where brick gives way to timber runs level at the height of the beam, and fixing your eye there makes the change legible. Because the building sits in the north-west corner, you need to work round to the west side of the Showa West Storehouse.

The yard can be entered during the hours of the Ogi Distillery in the converted part of the West Storehouse, 11:00 a.m. to 5:00 p.m. with irregular closing days. Whether you can walk as far as the north-west corner depends on the day, so ask at reception. No photography policy has been published. Directions and parking are set out on the Koyanagi Sake Brewery page. Details here were checked on 14 September 2026.