What is Shou Sugi Ban (Yakisugi)?

Historic Yakisugi in Kurashiki, Okayama, Japan

The story of yakisugi, or shou sugi ban goes back centuries  

Yakisugi is wall and ceiling cladding made exclusively from cypress and intensely burned as a preservative heat treatment through a traditional process that originated in Japan. 

Yakisugi is traditionally only used for wall, fence and ceiling cladding. The sugi in yakisugi refers to a particular wood species, the Japanese cypress, which is a strong and straight-grained softwood. Real yakisugi is never made from reclaimed wood, driftwood or chemically treated wood. It cannot be replicated without the traditional drying and contained heat-treatment processes.

Yakisugi has also been labeled as shou sugi ban outside of Japan, though to our knowledge, that term stems from a mistranslation of the original Japanese characters brought back by a non-native speaker. In the west, these two terms have the same meaning, but in Japan virtually nobody knows what shou sugi ban means.

For additional information, visit Yakisugi or Shou Sugi Ban? Learn What You Should Call it, and Why. 

How is shou sugi ban made?

Shiplap boards stacked up at our Japanese mill in Hiroshima

We start with careful log selection, grading for straightness and diameter. After the logs are cut into their final size and shape, they are then air dried. Once dried, the boards are ready for heat treatment. Enough contained heat is applied to the boards so that the excess wood fibers are burned off, which leaves us with an inky-black, thermally modified surface.

We manufacture three variations of yakisugi, with varying degrees of soot. The first, Suyaki™, is the original charred surface; this has an alligator skin-like texture. The thick layer of soot on the board remains intact. Gendai™ is brushed only once, which removes the alligator skin texture but leaves behind a dark surface. Pika-Pika™ is brushed twice, and has a distinctive, topographic texture which is lighter in color than the other two options.

How does the heat treatment work? Does the wood truly become a no-maintenance siding? 

Treating the wood with heat will improve the overall longevity of yakisugi as a siding material. During the heat treatment, hemicellulose, which is essentially a carbohydrate, is burned off. What’s left behind is the lignin, which is the structural component of wood. The end product is a hardened wood plank which is resistant to decay, insects and weathering. The soot layer increases the temperature threshold needed for combustion which dramatically reduces flame spread. 

Yakisugi is a low-maintenance wood siding. The thick soot layer on Suyaki™ will stay intact for 40-50 years, depending on site conditions. After that, the soot will begin to wear away, forming a beautiful patina unlike any other wood siding. 

Gendai™ and Pika-Pika™ will weather and gradually change in color, as with any other kind of wood siding. The change in color is inevitable and expected, we believe this rich patina-which only can be achieved through years of weathering-is an exercise in wabi sabi. In Japan, yakisugi is valued for its beauty. Re-oiling can be done to yakisugi to maintain the color, though we encourage waiting a few years before doing so.

What makes Japanese cypress best for shou sugi ban? 

Japanese cypress, or sugi,  is straight-grained, fast-drying, flexible, tannin-rich, and strong – all desirable characteristics for siding. It features a thick, dense latewood growth ring, which burns to a more substantial, longer-lasting soot layer. Compared to other species, its chemical properties respond well to fire and it becomes incredibly dimensionally stable when milled, dried, burned and quenched by traditional protocol.

While hardwoods or chemically modified woods with faux finishes might promise longer longevity, we have found that none live up to our environmental standards or respond appropriately to our traditional process. Japanese cedar is time-tested by centuries of Japanese tradition. We trust our siding to look great without any maintenance for its lifetime. 

Yaki means burnt, charred, or heat treated, and sugi refers to the cypress indigenous to Japan

Architectural Applications

Japan has influenced Western thought and design for over 100 years, and yakisugi has similarly contributed to modern architecture. Research indicates that Japanese plank burning technology transferred to siding applications from boat building traditions. Boats were built on dry docks, and their hulls were burned as a preservative before launch. 

In Japan, yakisugi is often combined with white stucco on exterior walls. Today, shou sugi ban is used in residential, commercial, and institutional applications as a sustainable alternative to carbon-intensive modern materials. Visit A Tour of Japan’s Historic Yakisugi to learn more, or check out our gallery below to see images of how yakisugi has been used in Japan for centuries!