Carbonized Wood: A Traditional Japanese Technique That Has Conquered the World

2023.08.21

Ancestral, vernacular, minimalist and harmonious. For many, these words have come to define the architecture of Japan, a country that has long served as a source of cultural and technological inspiration for countless societies worldwide. Popular Japanese techniques have reached even the most remote corners of the globe, gaining traction across various fields that range from technical craftsmanship to digital innovation. Within the realm of architecture, the appropriation and reinvention of various materials and construction systems –such as the use of carbonized wood in facades– has been an enduring theme.

Now more than three hundred years old, the popular technique is known in Japan as Shou Sugi Ban (also known as Yakisugi). It was first employed on the island of Naoshima to treat wood used in the construction of traditional fishing villages, with the goal of protecting the material from the damaging effects caused by the sea. The process originally involved burning the outer layer of the wood with fire, but has now evolved to charring the boards with a torch –by doing so, the material’s external fibers are forced to react, making the wood immune to termites, fungi and other natural forces for decades. It might sound strange at first: burning the wood to increase its durability. Nonetheless, it has proven to be completely true, so much so that the centuries-old method has become a sought-after resource in the architecture industry.

Below, we delve deeper into the wood carbonization process, its growing popularity in the field and widespread application in various regions around the world.

【 How does the carbonization process work and what are its benefits? 】
The procedure essentially consists of four steps, starting with the actual burning of the wood –this can be done either before installation or applied directly to the installed facade. A special grit is then used to brush the wood, removing the top carbon layer and giving the material its new shade. Once the wood is already black in tone, it receives a special waterproofing layer using cedar oil to ensure greater resistance, and finally receives a layer of sealant to avoid stains caused by the charred facades.

Wood is mostly structural lignin and hemi-cellulose carbohydrates. When the surface is charred, the cellulose layer burns off and the result is a wood siding that is resistant to many insects, weathering and fading, no matter the type of climate. It is also highly water-resistant; because the pores start to shrink and close while being charred, it’s much harder for the wood to soak up and take on water. And for that same reason, carbonized wood is also fire retardant. Quite ironically, by burning the wood, its softer outer layer is replaced by a new, stable and long-lasting carbon layer that prevents it from burning quickly.

"The technique of burning the surface of the wood improves performance in inclement weather, prevents decay, rotting, and insect infestation, and makes the wood more resistant to fire – Satoshi Kimura"

All of these conditions make Yakisugi treated wood extremely durable in various contexts and climates. As Satoshi Kimura, operations director at Japanese-based company Japan Yakisugi, explains, the technique can last for 80 to 90 years when properly maintained. In fact, “you can still see some old Japanese houses with over 120 years,” he says, whereas traditional wood siding is known to last around 20 to 50 years in average. In addition to its exceptional durability, the popularity of carbonized wood is also driven by its astounding organic beauty. A fusion of the modern and the elemental, elegant and with a reptilian-like texture, the material adds powerful aesthetic qualities to any project.

【 The art of Yakisugi and its growing popularity in contemporary architecture 】
One might wonder, why is such an ancient technique only recently becoming popular in the Western world? Previously used in vernacular buildings, Japanese architect Terunobu Fujimori is credited for appropriating the process of carbonized wood and innovating. His work gave notoriety to the technique, spreading it beyond the borders of Japan. Today, specialists like Chilean company WoodArch carry out the process in contemporary projects, reimagining and granting the Japanese craft a new value. “We are very interested, since many architects who know about wood are enthusiastic about the benefits and the fact that this wood can last 50 years,” says Andrés de Solminihac, Managing Partner at WoodArch.

With more specialists trained in the technique, this type of treated wood is present in a multitude of modern projects, all with different uses, across various geographical regions and adapting to a wide range of climatic conditions. Read on to explore how some of these use the material as a key element in their design.

- Weekend House in Kirishima / EAL, Japan -
This home in Kirishima, Japan, uses carbonized cedar boards as exterior cladding. Yakisugi was hand-made by everyone involved in the project, resulting in a traditional, yet contemporary look that displays a mesmerizing interplay of contrasting shades, evoking a sense of depth and sophistication.

- Platform House / studioplusthree, Australia -
A triangular, second-story house located in Sydney, Australia, the Platform House is clad in charred timber that accentuates the volume’s shape and contrasts with its pale interior. “We chose Shou Sugi Ban to create an exterior that was low-maintenance, but also had a natural patina and texture that could change very subtly over time,” says architect Simon Rochowsky.

- RT Residence / Jacobsen Arquitetura, Brazil -
The main finishes in this contemporary residence are charred wood and travertine marble. A dark exterior completes the building’s natural color palette, complementing the green, beachy landscape characteristic of Brazil’s Laranjeiras neighborhood.

- Shangri-la Cabin / DRAA + Magdalena Besomi, Chile -
Located in the native woodland of Coihueco Chile, the interior of this mountain cabin is clad with timber planks from local trees, whereas the exterior features charred pine planks following the Yakisugi principle.

- ASI Reisen Headquarters / Snøhetta, Austria -
Slightly charred and thus carbonized, the facade of this four-story office building in Austria is waterproof and durable without the need for further painting, as well as providing protection against insects.

- Kuku-Ranna Summer House / Arhitektuuribüroo Eek & Mutso, Estonia -
This minimalist, tent-like summer house in Vääna-Jõesuu, Estonia, features a wooden facade with Yakisugi finishing that blends in with the surrounding pine tree trunks. The side elevations exhibit a dark burnt texture while the charred layer on the sloping surfaces has been partly washed away and is thus greyish in color.

- Burnt Wood Office / STEINMETZDEMEYER, Luxembourg -
As its name suggests, the office building’s envelope is made with charred regional larch cladding, known for its resistance and characteristic dark shade that stands out in Luxembourg’s Bonnevoie district.

- Forest Retreat / Uhlik architekti, Czech Republic -
This forest retreat is composed of a compact enclosed volume covered in charred boards with rabbet joints. The wood for the boards and joists was taken from fallen trees from the owner’s land, hence seamlessly blending into the surrounding landscape.

- La Dacha Mountain Hut / DRAA, Chile -
Found among the native woodland overlooking the impressive Nevados de Chillan volcanic complex, La Dacha Mountain Hut uses onsite charred conifer planks, mounted as a ventilated facade that insulates while preventing the use of chemicals.

- Villa Meijendel / VVKH architecten, The Netherlands -
In the Dutch town of Wassenaar, right where a dense forest opens to a dune valley, lies Villa Meijendel. Its blackened facade changes according to light: at night, it’s almost invisible against the dark edge of the forest; during the day, the somewhat glittering surface sparkles with sunlight.
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▪ Source: Archdaily｜https://www.archdaily.com/880330/carbonized-wood-a-traditional-japanese-technique-that-has-conquered-the-world

▪ Words: Valeria Montjoy

▪ Photography Credit: © Shigeo Ogawa, © Christian van der Kooy, © Brett Boardman, © Toomas Tuul, © Jan Kuděj, © Felipe Camus,© STEINMETZDEMEYER