• Kumiki (Joinery)
Why Kumiki (Joinery) attracts a lot of people? Let’s deep dive into the world of Kumiki

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Hello! I am Hide, the chief craft man of the wood-workshop at Hidakuma / FabCafe Hida.
A 30-second walk away from the FabCafe Hida, there is a museum of kumiki (interlocking wooden building blocks), one of few in the world.
The “Hida Artisan Culture Center” is an institution that was built about 28 years ago to preserve the history, technology and wisdom of Hida artisans.

The center also has a corner where you can try your hand at putting together kumiki and houndstooth pattern puzzles.

Displayed in the center are examples of “kumiki” that are used in traditional wooden houses, old carpenter’s tools, and the like, and their number is said to be unrivalled in Japan.
Now I will introduce you to some of the unique kumiki displayed in the “Hida Artisan Culture Center.”

What is Kumiki?

These days, attention has focused from all over the world on kumiki that are used in traditional Japanese houses.
Kumiki is a wooden building technology where grooved wood pieces are joined together to form sturdy three-dimensional objects, and making it possible to produce longer pieces. Its history goes back as far as the Heian Period.
In Hida region, dwellings and temples were built using kumiki from ancient times, and the technology was handed down from father to son and developed to such an extent that a carpenters’ quarter came into being. In the process, intricate and abstruse kumiki were produced in great numbers as patterns and demonstrations of artisans’ expertise and wisdom.

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Five reasons why Kumiki attract people 

Houses are built by combining wooden joints, without using ironware like nails and bolts, Why is it that attention has now focused on such a cumbersome (?) technique? There are these excellent reasons listed below.

1. Exceptional strength can be achieved

In the process of connecting squared timber pieces together, it is required as a matter of course that the junctions be strong. The strength achieved by making different squared timber pieces as if one dissipates vibrations and shocks, and is designed to remain high. Nowadays, it is usual to use the so-called “conventional method of construction,” which uses ironware like screws and bolts. However, there is a risk that, because of corrosion and wood aging, the ironware will become loose and the strength will deteriorate.

Internal structure of the Hida Takumi Culture Center. This facility does not use any hardware, and buildings are made up of only group trees.

2. Extending wood material is enabled

The length of timber is limited. However, by using joints it is possible to make a 1-meter piece as long as 3 meters. It is possible to make timber pieces of any length while imparting them strength.

This is a picture of part of a piece of furniture made of short squared timber pieces, 30 mm x 30 mm x 1,0 m (1.2 inches x 1.2 inches x 3.28 feet), joined together by seat-peg joints to be 4 m (13.12 feet) long.

3. Can be renewable and recycled by removing a rotten part

All materials decay with time. However, it is possible to remove a decayed part, make a kumiki, and substitute the new part. This is also a reason that wooden structures are some of the longest-lasting ones in the world.

The FabCafe Hida built over 100 years ago, was in a state where the columns had rotted so much that the structure could not stand erect. Then, only the rotten parts were removed and replaced with peg-anchored mortised rabbeted oblique scarf joints.

The contrast of the old and the new part is accomplished extremely beautifully.

4. Can be recycled and reconstructed (through the process of dismantle, move and rebuild)

“Relocation and reconstruction,” where a house is dismantled and built again in another place, has been done from time immemorial. At present, too, the number of people is also growing who settle in old Japanese-style houses that have been relocated after becoming vacant. This is also possible only because they are built without using nails.

The scene of dismantling an old Japanese-style house built 150 years ago.

A popular folk craft shop in Hida has been born again as “Yawaiya” and lived in by generation after generation.

5. The technique that only artisans knowledgeable of wood can attain

Wood is a living thing. Therefore, it should be used in such a way as to stay strong as long as possible and preserve its beauty after the artisan examines its grain direction and natural wear and tear. This kumiki technique is exactly a technique that highly skilled artisans have developed while making good use of the properties of wood.

A carpenter carefully marks a piece of timber after examining the shape and grain of the wood.

A selection of nine types of unique kumiki that are preserved in the “Hida Artisan Culture Center”

At the “Hida Artisan Culture Center,” you can thoroughly enjoy Hida artisanship, from quite imaginative kumiki from a structural point of view, to unique kumiki overflowing with the playfulness of the artisan, to abstruse kumiki that pose a challenge to modern artisans. Now I will introduce you to some of them!

Isuka-Tsugi (crossbill joint)

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This is said to be a construction term that refers to a state resembling the widely open bill of a crossbill, a bird species. As can be seen, the diagonally cut joint actually resembles the bill.
This joint is said to be used in connecting thin squared timber pieces like ceiling poles over long distances, and to be capable of withstanding the load from the part above. It is said that the cleanly cut diagonally connected pieces, because they are beautiful to look at as well, are also used as “decorative joints” often employed in patterns in parts that are visible.


Isuzaka Shachi (Crossbill + Shachi)

 "image2 "Shachi is a thin dowel inserted into both mortise and tenon. This is a joint with an increased strength thanks to the dowel additionally inserted into the crossbill joint. (It is said that essential shachi parts have gone out of stock …)

Koshikake-Ari-Tsugi (half-lap, dovetailed joint)

 "image20 "Koshikake is the convexo-concave part at the bottom of the picture, and the ari is a joint shaped like a trapezoid. This half-lap, dovetailed joint is the combination of these two. It is a joint principally used as a horizontal coupling in buildings, capable of withstanding the load and tensile stress from the part above.


Dokko-Gumi assembly

 "image10 "This is a coupling that reproduces the joints used in the Otemon at the Osaka Castle. It is said that, at the time, the inner structure was not clear from the joined state, and it was investigated using X-ray analysis. It is an extremely abstruse kumiki that does not move either horizontally or vertically.


Shiho-Kanawa (all-direction iron ring)

 "image 11 "This is the mortised rabbeted oblique scarf joint most often seen on television, and is known as the strongest joint capable of withstanding loads from all directions. However, this all-direction iron ring is extremely peculiar, with all four sides forming an iron ring and, if looked at in a joined state, it is quite impossible to understand which direction it has been inserted from. This configuration should be possible by inserting it diagonally, and it can already be perfectly called an instance of the carpenter’s playful mood.



 "image6 "This is a joint used in connecting a vertical axis and a horizontal axis. It is a tricky structure that is immobilized by sliding the ogi, or the tenoned section (the male part. The female part is called megi). It is easily dismantled by sliding in the opposite direction.



 "image7 "This is a joint with the tenoned section partially removed, into which the other part is further secured with a dovetail joint. The dovetail joint has the property of withstanding tensile stress, but is not capable of withstanding other loads, so it seems it is often reinforced by being combined with other joints.


Shiho-Henkei (omnidirectionally transformed joint)

 "image1 "The all-direction transformed joint is a joint that uses a different joint on each side; in a connected state it is impossible to understand how it has been connected. It is said that such a tricky joint was more often used for decorative rather than structural purposes and, in particular, was used in special places such as temples and castles. Its marvelous appearance, impossible at first sight, is thought to have been used as a charm against evil.


Extra item: Testing carpentry skills

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This is said to have been used in skills tests for young carpenters. It is said that among them there was a skills test for olden-time carpenters which condensed their know how of basic joints and connections to see whether they could produce them correctly in as short an amount of time as possible.

How was it? The kumiki, inherited from the ancient times, have something new to show and teach whenever you look at them, and afford an insight into the techniques, ingenuity and mind of ancient carpenters. These are by no means a legacy of the past, but have ample room to be updated and adapted to the modern life. Nowadays, the potential of such kumiki has been attracting much attention.

Hida's Kumiki crosses the ocean to Milan Salone 2018!

Replica of the Kumiki from the Hida Artisan Culture Center will be displayed at Milan Salone, held in April, 2018.
The exhibition called “U-JOINTS” will take place in Spazio Maiocchi, a new space in the heart of Milan.

U-JOINTS is the exhibition where 30 international contemporary designers exhibit their prototypes and conceptual pieces. It shows how designers appropriate standard connectors, assemble and personalize them to create unique objects and sheds light on designers who invent new joinery from scratch.

Date: April 17 to April 22, 2018
Venue: “Spazio Maiocchi,” Milan, Italy


Deep dive into the world of Kumiki while staying at the FabCafe?

At FabCafe Hida, we provide the learning experience and environment of the Kumiki from program curation, coordination and execution. You can not only see the variety of Kumiki at the Takumi museum, but also actually learn the practical skill of making joinery by the craft men and also prototype at the FabCafe Hida where you can access to the tools, wood working and Fab machines and knowledgable artisans. 

For details, click here .