What Is Yakisugi (Shou Sugi Ban)?

Yakisugi (incorrectly called shou sugi ban) is a traditional Japanese shiplap or square-milled plank wall cladding that has been heat treated on the outward face.  In Japan it is commonly used in combination with white stucco in various ratios for exterior wall surfaces, each region having a slightly different aesthetic.  Some regions clad the entire structure with siding, some only wainscoting under a stucco upper wall, and some regions clad up to the shadow line below the roof overhang.  It is installed vertically or horizontally, and is also often used as a cosmetic roof deck on exposed eaves.  Please see our historical gallery of pics below to see how it weathers.

Japan has influenced western design in surges over the past 150 years, the yakisugi aesthetic having been brought into modern global architecture in the form of a black monolithic surface.  Yakisugi is starting to be accepted worldwide as a technically and cosmetically desirable wood cladding, but has often been interpreted as a chic, high-design building material.  In its home market however, it is simply standard, utility wood siding, affordably priced and with improved longevity over untreated wood.

There is a lot of information in the public domain on the traditional manufacture of yakisugi (see Youtube), as well as several common misconceptions.  The wood is holistically produced starting with log selection, then resaw pattern, natural drying, charring, and brushing by traditional methods.  Note yakisugi is a product, not a burnishing technique applied to any lumber.  Traditionally three planks were tied into a triangle tube and the interior lit on fire before opening and quenching with cold water when ready.  Nowadays planks are charred in a kiln for volume production, then the surface can be left as-is or the sooty outer layer brushed off to achieve various looks.  Common misunderstandings are that various species can be used for yakisugi (only cypress works well), that burning with a torch effectively heat treats the wood (it only produces an uneven cosmetic burnishing), that any dimension can be treated (only thin stock planks not western thickness standards or beams) and that there are light, medium, and heavy levels of charring to achieve the different finishes (authentic cladding is all heat treated then brushed afterwards to get varied cosmetic results).  If the traditional know-how is not specifically followed then there will be problems with dimensional stability, soot surface longevity, finish longevity, and wood integrity.

The heat treatment improves the lifetime of the planks by preventing decay and rot, discourages insect infestation, improves dimensional stability, and improves flame retardant properties.  Wood is made up of fibrous lignin and metabolize-able cellulose, and heat treatment leaves the structural lignin intact while neutralizing the cellulose.  Since cellulose contains the sugars so desirable to insects, bacteria, and fungus, heat-treated wood will last longer than untreated wood.  While the evidence of this on yakisugi siding comes from case studies in Japan, there is technical information on the Thermowood website here.  Note that yakisugi is not the same as thermally modified wood from the Finnish process, though it exhibits similar characteristics due to heat-treatment.

Please see additional information on the Who We Are and FAQ pages.

Yakisugi or Shou Sugi Ban is a traditional Japanese shiplap or square-milled plank wall cladding that has been charred on the outward face.  In Japan it is commonly used in combination with white stucco in various ratios for exterior wall surfaces, each region having a slightly different aesthetic.  Some regions clad the entire structure with siding, some only wainscoting under a stucco upper wall, and some regions clad up to the shadow line below the roof overhang.  It is installed vertically or horizontally, and is also often used as a cosmetic roof deck on exposed eaves.  Please see our historical gallery of pics below to see how it weathers.

Japan has influenced western design in surges over the past 150 years, the yakisugi aesthetic having been brought into modern global architecture in the form of a black monolithic surface.  Yakisugi is starting to be accepted worldwide as a technically and cosmetically desirable wood cladding, but has often been interpreted as a chic, high-design building material.  In its home market however, it is simply standard, utility wood siding, affordably priced and with improved longevity over untreated wood.

There is a lot of information in the public domain on the traditional manufacture of yakisugi (see Youtube), namely tying three planks into a triangle tube and lighting the interior on fire before opening and quenching with cold water when ready.  The planks can also be burnished with a propane torch or sent through a kiln for volume production.  The charred surface can be left as-is, or the sooty outer layer brushed off for a more finished look.

The charring is not only cosmetic in effect.  It improves the lifetime of the planks by preventing decay and rot, discourages insect infestation, improves dimensional stability, and improves flame retardant properties.  Wood is made up of fibrous lignin and metabolize-able cellulose, and heat treatment leaves the structural lignin intact while neutralizing the cellulose.  Since cellulose contains the sugars so desirable to insects, bacteria, and fungus, heat-treated wood will last longer than untreated wood.  While the evidence of this on yakisugi siding comes from case studies in Japan, there is technical information on the Thermowood website here.  Note that yakisugi is not the same as thermally modified wood from the Finnish process, though it exhibits similar characteristics due to heat-treatment.

Please see additional information on the Who We Are and FAQ pages.

Historical Gallery