The meaning of "Sugi" in Yakisugi / Shou Sugi Ban

Martin Gottschlich

Beautifully charred cladding boards, produced according to ancient tradition – what are they made of and what do the terms describing them mean?

You probably may already know, but we are Nakamoto Forestry, the primary producer of Yakisugi or Shou Sugi Ban, one of the longest-lasting and most gorgeous building materials on earth.

But what it is about with “sugi”, appearing in the middle of both terms? We are talking about a tree species, Japanese cypress.

The “sugi” in “Yakisugi” and “Shou Sugi Ban” is a species of tree

Cryptomeria japonica, also commonly referred to as Japanese Cedar or Japanese Cypress, is actually a monotypic genus in the cypress family. Native to Japan, where it covers much of the mountainous country, it’s primarily managed and harvested for timber. The entire country was replanted post-war, and the Japanese timber industry is larger than most westerners realize. There are still a few old growth stands with trees over 2 000 years old, the most famous being Yaku-shima, an island off the southern tip of Kyushu.

What Makes Cypress Durable?

Sugi trees grow straight and fast, up to about 60 metres tall when mature. The wood is fragrant, naturally rot and insect resistant, and does not easily mildew or stain blue (i.e. blue mildew stain which is why many species such as pine are generally painted and not oiled if used for cladding at all), due to a very high tannin content. The bark is soft and fibrous, and the tiny, needle-shaped leaves grow radially from each twig.

The harder, summer growth rings (“late wood”) are thicker than with cedar or larch or many other species, which is critical for our heat treatment process. With many other trees, the soot will erode off almost immediately since it’s so soft, whereas cypress produces a more substantial soot layer that lasts decades without maintenance. Sugi has a Janka hardness ranging from 320–350 and is used for all types of construction applications, ranging from framing, to flooring, to wall cladding, to roof decking, to shingles.

Responsible forest management

Most of the timber products we produce comes from Sugi grown in forests that the Nakamoto family has managed since at least 1949. These forests must be pruned and thinned, with care taken to clear weeds and ivy away from younger trees that might be negatively affected. Snow is also cleared to promote growth and health. We now own and carefully manage 2 000 hectare of timberland in the Hiroshima and Tokushima regions. Our focus is now directed toward mature growth and larger-diameter logs. If we continue to responsibly manage our forests, we can reach a felling age of 100 years, thus improving the quality of our product while also protecting our valuable natural resources. Therefore, SGEC / PEFC certification for our forests have just been renewed end of 2019. They are proof of our efforts in sustainable forest management.