Yakisugi Introduction
Yakisugi (often mispronounced as “shou sugi ban”) is a traditional Japanese wall and ceiling cladding made exclusively from cypress and intensely burned as a preservative heat treatment. The heat treatment improves siding longevity by preventing decay and insect infestation, makes the planks more dimensionally stable, and improves fire retardancy. Yakisugi is a maintenance-optional exterior wood siding, either re-oiled periodically to slow down the weathering process, or simply replaced after it’s lifetime is reached.
Traditionally in Japan yakisugi is combined with white stucco on exterior walls, each region having a different design aesthetic. Today it is used in residential, commercial, and institutional applications as a healthy, sustainable, and beautiful alternative to inorganic, carbon-intensive modern materials. It is installed as exterior siding either vertically or horizontally, and is also used as exposed roof deck, soffit, and interior wall and ceiling paneling.
The Technical Background
Though hinoki cypress, pine, larch, oak, and other species are abundant in Japan, yakisugi is only made from sugi cypress. Cypress is straight-grained, fast-drying, flexible, tannin-rich, and strong—all desirable characteristics for siding. It has a thick, dense latewood growth ring, which burns to a more substantial, longer-lasting soot layer.
By weight wood is mostly structural lignin, with the balance hemi-cellulose carbohydrates that are food for fungi and insects. Heat treatment of yakisugi burns off the cellulose, minimizing rot and infestation. The heat treatment also case hardens the planks, and in combination with air drying, reduces dimensional movement in severe weather exposure. The soot layer increases the temperature threshold needed for combustion, dramatically reducing flame spread. The hydrophobic soot layer and hardened surface slow down weathering, making it maintenance-optional.
Yakisugi Influence on Western Architecture
Japan has influenced western thought and design since the country opened up 150 years ago (see this blog), and yakisugi has significantly contributed to modern architecture in the form of the contemporary black monolithic wall aesthetic. Yakisugi material itself is finally starting to be accepted worldwide as a sustainable and cosmetically desirable wood cladding option. It has often been interpreted as a chic, high-design building material, but in its home market it is standard, utility wood siding, affordably priced and with improved longevity over untreated wood.
How Yakisugi is Made and Customized
Historically, yakisugi has been made by the project general or siding contractor on each jobsite. Only in the last several decades has yakisugi manufacture transitioned to lumber mills such as us, and this is due to modernization of the construction market.
There is a lot of information in the public domain on the traditional manufacture of yakisugi, as well as several common misconceptions. A holistic and narrow manufacturing protocol has been developed over hundreds of years to ensure dimensional stability and maximum longevity. Yakisugi is a product, not a burning technique.
The process starts off with careful log selection, grading for straightness and diameter, grain density and quality, and wood color. The logs are resawn plain or quartersawn only, and the moulder blanks are air or sun dried, not by kiln. The heat treatment is intense and the wood is quenched at the right moment. After drying again, the wood can be used as-is or brushed to nock down the soot layer in order to achieve the desired appearance.
Standard traditional products include Suyaki (original charred), Gendai (brushed once), and Pika-Pika (brushed twice).
Misconceptions in the West
The heat treatment of wood has been common around the world in various applications for millennia. Japanese yakisugi is only one of many variations and has very specific manufacturing parameters and applications. Here are the most common misunderstandings of yakisugi we have come across, as well as explanations:
Various species can be used for yakisugi. In our experience the traditional guidance of using only specific types of cypress works well. While heat treatment works well on many types of wood, such as thermal modification by the Finnish process, cypress works best for the Japanese high-heat, thin-plank cladding technology.
Burning can done with a torch. There must be a contained fire to reach a temperature necessary to optimally carbonize the wood surface. Using a weed burner does not allow intense enough heat to get consistent treatment due to density variation plank to plank or heartwood to sapwood. A similar appearance can be achieved but poor quality of the soot layer allows for premature weathering.
Any dimension can be surface-treated. Burning the surface of any dimension of most materials will generally make it hydrophobic and case hardened. However, yakisugi or “shou sugi ban” is a Japanese product defined by a narrow specification parameter. The high heat makes dramatic moisture content differences core to surface on material more than around 9/16” (15mm) thick, causing thick stock such as ¾”, 4/4”, 5/4”, 6/4”, or 8/4” to dramatically warp and twist. Very large timbers may not move in the same way, but burning large timbers is not done in Japan and is not yakisugi. Surface treatments for furniture or artisan applications is beautiful and fun, but is also not yakisugi.
There are light, medium, and heavy levels of charring to achieve the different finishes. All yakisugi surfaces start off with the planks being deeply heat treated to a Suyaki surface, then brushed afterwards with different brushes to achieve Gendai and Pika-Pika type surfaces.
Yakisugi stays the same appearance a long time without maintenance. This is true for Suyaki since the thick soot layer will keep the same color for 40 to 80 years depending on quality and site conditions. However, the Gendai and Pika-Pika brushed surfaces will weather in color same as any kind of wood material. To keep the color consistent over time a re-oiling schedule is necessary.
Please see additional information on the Who We Are and FAQ pages.
Yakisugi Introduction
Yakisugi (often mispronounced as “shou sugi ban”) is a traditional Japanese wall and ceiling cladding made exclusively from cypress and intensely burned as a preservative heat treatment. The heat treatment improves siding longevity by preventing decay and insect infestation, makes the planks more dimensionally stable, and improves fire retardancy. Yakisugi is a maintenance-optional exterior wood siding, either re-oiled periodically to slow down the weathering process, or simply replaced after it’s lifetime is reached.
Traditionally in Japan yakisugi is combined with white stucco on exterior walls, each region having a different design aesthetic. Today it is used in residential, commercial, and institutional applications as a healthy, sustainable, and beautiful alternative to inorganic, carbon-intensive modern materials. It is installed as exterior siding either vertically or horizontally, and is also used as exposed roof deck, soffit, and interior wall and ceiling paneling.
The Technical Background
Though hinoki cypress, pine, larch, oak, and other species are abundant in Japan, yakisugi is only made from sugi cypress. Cypress is straight-grained, fast-drying, flexible, tannin-rich, and strong—all desirable characteristics for siding. It has a thick, dense latewood growth ring, which burns to a more substantial, longer-lasting soot layer.
By weight wood is mostly structural lignin, with the balance hemi-cellulose carbohydrates that are food for fungi and insects. Heat treatment of yakisugi burns off the cellulose, minimizing rot and infestation. The heat treatment also case hardens the planks, and in combination with air drying, reduces dimensional movement in severe weather exposure. The soot layer increases the temperature threshold needed for combustion, dramatically reducing flame spread. The hydrophobic soot layer and hardened surface slow down weathering, making it maintenance-optional.
Yakisugi Influence on Western Architecture
Japan has influenced western thought and design since the country opened up 150 years ago (see this blog), and yakisugi has significantly contributed to modern architecture in the form of the contemporary black monolithic wall aesthetic. Yakisugi material itself is finally starting to be accepted worldwide as a sustainable and cosmetically desirable wood cladding option. It has often been interpreted as a chic, high-design building material, but in its home market it is standard, utility wood siding, affordably priced and with improved longevity over untreated wood.
How Yakisugi is Made and Customized
Historically, yakisugi has been made by the project general or siding contractor on each jobsite. Only in the last several decades has yakisugi manufacture transitioned to lumber mills such as us, and this is due to modernization of the construction market.
There is a lot of information in the public domain on the traditional manufacture of yakisugi, as well as several common misconceptions. A holistic and narrow manufacturing protocol has been developed over hundreds of years to ensure dimensional stability and maximum longevity. Yakisugi is a product, not a burning technique.
The process starts off with careful log selection, grading for straightness and diameter, grain density and quality, and wood color. The logs are resawn plain or quartersawn only, and the moulder blanks are air or sun dried, not by kiln. The heat treatment is intense and the wood is quenched at the right moment. After drying again, the wood can be used as-is or brushed to nock down the soot layer in order to achieve the desired appearance.
Standard traditional products include Suyaki (original charred), Gendai (brushed once), and Pika-Pika (brushed twice).
Misconceptions in the West
The heat treatment of wood has been common around the world in various applications for millennia. Japanese yakisugi is only one of many variations and has very specific manufacturing parameters and applications. Here are the most common misunderstandings of yakisugi we have come across, as well as explanations:
Various species can be used for yakisugi. In our experience the traditional guidance of using only specific types of cypress works well. While heat treatment works well on many types of wood, such as thermal modification by the Finnish process, cypress works best for the Japanese high-heat, thin-plank cladding technology.
Burning can done with a torch. There must be a contained fire to reach a temperature necessary to optimally carbonize the wood surface. Using a weed burner does not allow intense enough heat to get consistent treatment due to density variation plank to plank or heartwood to sapwood. A similar appearance can be achieved but poor quality of the soot layer allows for premature weathering.
Any dimension can be surface-treated. Burning the surface of any dimension of most materials will generally make it hydrophobic and case hardened. However, yakisugi or “shou sugi ban” is a Japanese product defined by a narrow specification parameter. The high heat makes dramatic moisture content differences core to surface on material more than around 9/16” (15mm) thick, causing thick stock such as ¾”, 4/4”, 5/4”, 6/4”, or 8/4” to dramatically warp and twist. Very large timbers may not move in the same way, but burning large timbers is not done in Japan and is not yakisugi. Surface treatments for furniture or artisan applications is beautiful and fun, but is also not yakisugi.
There are light, medium, and heavy levels of charring to achieve the different finishes. All yakisugi surfaces start off with the planks being deeply heat treated to a Suyaki surface, then brushed afterwards with different brushes to achieve Gendai and Pika-Pika type surfaces.
Yakisugi stays the same appearance a long time without maintenance. This is true for Suyaki since the thick soot layer will keep the same color for 40 to 80 years depending on quality and site conditions. However, the Gendai and Pika-Pika brushed surfaces will weather in color same as any kind of wood material. To keep the color consistent over time a re-oiling schedule is necessary.
Please see additional information on the Who We Are and FAQ pages.