Dichen Ding is an Architectural Designer in New York City. She was born in China, received her Master of Architecture from Columbia University and is currently working for TEN Arqitectos.
It’s said Japan is a country “where wood has a soul,” so it’s no surprise that Japan also enjoys the most advanced wood construction techniques in the world. Their designs can range from elegantly simple to devilishly complex. These joints aren’t just beautiful decorative features but functional and vital structural elements. Moreover, they’re hardly relics of the past: they still inspire contemporary architects. This essay will explore some of the earliest and most exquisite examples of wood joinery then highlight their influence on recent architectural projects by world-famous architects.
Top Image: Yusuhara Wooden Museum Bridge by Kengo Kuma & Associates. Image courtesy of Kengo Kuma & Associates.
How did Japan’s highly developed joinery techniques come about? First and foremost, Japan historically enjoyed abundant timber reserves and almost exclusively concentrated on wood construction. Additionally, the country’s regular typhoons and earthquakes made wood the preferable choice: its smaller mass is more capable of withstanding earthquakes as compared to stone or brick construction. When an earthquake hits, the wooden joints function as a kind of shock absorber, thus affording the building a certain amount of flexibility. Moreover, the fact that Japan’s native timber has a natural resistance to attack by bacteria, fungi, and insects – Japan’s native termites are harmless too – makes wood an even better option as building material.
Early iconic examples of Japanese joinery can be seen in the seventh and eighth-century structures at the Nara temples Horyu-ji (Figure 1), Toshidai-ji and Shin Yakushi-ji. These reflect the Japanese adaptation of architectural forms introduced from China at that time. Even in these early structures we can see evidence of advanced wood construction techniques. These ancient buildings are living examples of the amazing woodworking techniques in Japan at that time. Although there are many kinds of joints used in the construction process of these temples, the most widely used joints are the mortise and tenon joint.
The mortise and tenon joint is a very simple form used by woodworkers worldwide. The basic design has two parts: the mortise hole and the tenon tongue, as Figure 2 indicates. A protruding tenon, cut at the end of one piece, fits into a corresponding recess, called a mortise, in the other. This joint is a staple in the construction of furniture, interior elements (e.g. frames and windows), and structural members such as beams and roof frames. The mortise piece and tenon piece are made to interlock with perfect fit, without using fasteners or glues, enabling the wood to expand and contract when humidity.
Another commonly used joint is called the Dovetail. This joint is very popular for its resilience against being pulled apart: finger-like joints (called pins and tails, the latter of which resembles the dove’s tails) interlock to enable a tight, strong and long lasting fit. These also require zero mechanical fasteners, making them more attractive to the traditionalists who are trying to achieve a pristine look. People often use dovetail joints to build drawers and corners of furniture or to further strengthen a rigid framework.
In Japan, however, these basic joints evolved to be used in a building’s core structure. These joints (e.g. sleepers, joists, and posts) can be quite complicated, particularly when two, three, or even four members intricately join in a single post. One example is a kind of joint called sampo-zashi, which is a three-member joint (Figure 6). Normally, a key or wedge is used to lock these joints firmly together, and since they can be exceptionally complex, sometimes false or inserted tenons are used instead of the genuine tenons illustrated. This kind of joins is rather weak and must be reinforced with metal.
There are thousands of various kinds of joints that are used in Japanese architecture, above are just some very basic examples of them. But this evolution continues today as architects are still developing new and innovative designs for joints that add structural strength and aesthetic value.
Kengo Kuma is one contemporary architect who has incorporated new wooden joinery techniques in his projects. Kuma is famous for pursuing and experimenting on new materials during his design process. He revisits traditional architectural ideas and explores how to integrate them into modern life. For example, his Visitor Center in Tokyo looks like a series of traditional Japanese houses stacked together. The project integrates the pitched roof element that’s commonly seen in old Japanese houses and uses it to define and provide significant features to the modern program and space in a very intriguing way.
The Opposite House Hotel he designed in Village, Beijing also has amazing interior designs. The atrium in the middle of the lobby brings light all the way into the space. When you travel up in the elevator, the veil-like fabric hanging in the atrium expand and pass by like layers of mists, changing the light and the experience all the time. Kuma pays a great deal of attention to the overall structure and small details alike. Most importantly, he is also interested in the aesthetic effect of the simple wood frame construction.
The Yusuhara Wooden Bridge Museum (built in Sept, 2010) is a fascinating wooden structure project by Kuma. This bridge links two public buildings which had been long separated by a road running between them. Kuma came up with a simple post and beam wood frame construction, one that would exhibit a harmonious relationship with its forested mountain environment. The use of large-scale steel or concrete elements was avoided in favor of the small members of glue-laminated local cedar. In order to achieve its 47 meter span, an innovative system of interlocking beams was developed, reinterpreting the traditional Japanese cantilever.
Long beams rest above progressively shorter ones, and the entire structure tapers to a point at a central steel-cored wooden column. The two skeletal metal towers supporting the bridge on either end merge visually with their wooded surroundings, evoking the impression that the massive structure is balancing on one slender post. The interior of the gallery mimics the exterior in its materiality and poetic exposed structure, forming a space framed by cedar members and a panoramic view of the landscape. The stunning project is reminiscent of the exposed layered structures found in traditional Japanese architecture as well as the central pillar pagodas used in shrines.
Although the play of wood joints in the structure is not that complicated, the ways the columns and beams are put together are also very interesting. There also exists a mixture of different kinds of materials: the central wooden column, built in a cruciform shape, is screwed into a hidden welded steel base. The column’s core is actually hollow and contains a reinforcing steel column while central beams run through the steel columns uninterrupted. The beams below the floor slab are prevented from shifting by the weight of the structure above them. Above the floor slab, the weight on each joint lightens and the beams are just held in position by a bolt drilled up through the beam below it.
In the project of GC50th Anniversary Memorial built in 2010, Kuma uses a grid system of thin timbers to build a hall 30 feet tall. His experiments prove that the timbers can bear 1 ton of weight by grappling each other while using only 4 percent of volume they create. Additionally, this building directly uses the structural system for its facade, showing the public its interior organization and creating a stunning street presence. The assembly of wood sticks is also very easy: one simply rotates and presses the stick until it falls into a carved-out part of another stick. The structure can be extended without any nails or metal fittings. The cube constructed by the timbers also becomes the grid on its own for the showcase in the museum.
Another very inspiring architect to look at is Shigeru Ban. The Pritzker prize laureate uses unique materials in his design. He is called the “Paper Architect” due to the fact that he often uses recycled cardboard, paper and old beer crates in his design for emergency shelters as well as high-end museum and pavilions. Ban believes that the value of architecture lies in its necessity: he builds what people need and he uses the best material suitable to the context and economy. The relative ease and sustainability of timber buildings’ construction and maintenance process is the biggest advantage of the material. Ban thinks that wood engineering in Switzerland is at the highest level and therefore, when he was working on the Tamedia Office Building, he chose wood as the main building material.
In Ban’s design for Tamedia Office Building, the client asked Ban to design a wide open office building where they could easily reconfigure and rearrange their workspace. Ban wanted an environmentally friendly design – one that used wood construction – but he faced immense challenges: wood doesn’t easily span large spaces. So, the architect developed a system of joinery that consisted of pin joints and a large portion of prefabbed wood pieces. The core concept is in their assembly: they can be put together systematically and, if necessary, the pieces can be replaced relatively easily. The requirement for high precision and quality goes without saying in a situation like this.
The use of pin joint (also called a revolute joint or hinge joint) not only provides the building with a unique and friendly look, but also creates a certain tolerance in the joint to allow for small amount of freedom when the materials fit together, which as mentioned above, improves the stability of the overall structure. The fact that the pieces are replaceable allows the beams to be made from an entire piece of timber. The integrity of the material and the design pushed the wood beam’s capacity to the limit but created the open space required by the client.
All the joints are consisted of the same material: pine wood. The wood splices have no metal parts, resulting in amazing details in the structural system which, when exposed, gives a very special character and unique spatial experience. The fact that the building skin is entirely glass reinforces the expression of the wood joinery. The materials were all selected with consideration to meet the requirements of the Swiss government’s regulation for energy consumption. At night, when people are working late, the warmth of the materials radiates through the transparent glass facade, telling the city about the inner life of the building. It is an economic, considerate, functional and beautiful building. In a way, this building is a perfect example of Shigeru Ban’s concept for architecture in general as well as a perfect example of how architecture should be.
Joinery is an amazing component in Japanese woodwork and in the history of craftsmanship. It’s encouraging and exciting to see how Japanese architects take this technique and apply it with modern technology and innovations. The evolution of the technique – and art – of joinery and woodwork isn’t over.
1. Studies in Organic, Kengo Kuma & Associates, TOTO Publishing
2. Analysis of Material Practice in The Works of Kengo Kuma, Market Modernization
3. Japanese Designer Kengo Kuma’s Matrix Of Wood Planks Results In An Ultra-Cool New Starbucks In Dazaifu,
5. The Complete Japanese Joinery [Paperback], Hideo Sato (Author), Yasua Nakahara (Author), Koichi Paul Nii (Translator)
6. Art Of Japanese Joinery [Paperback], Kiyosi Seike