The story of burning timber cladding is centuries old.
What is Yakisugi?
Yakisugi (Shou Sugi Ban ) is fence, ceiling or weatherboard cladding made exclusively from Japanese Cypress(Japanese Cedar) by fire conditioning that timber under immense heat. This serves as a preservative fire conditioning the wood through a traditional Japanese process.
What isn’t Yakisugi ?
Yakisugi (Shou Sugi Ban ) is a timber board product either 1 or 2in (25-50mm) thickness only used for wall, fence, ceiling cladding, or landscaping it is not a burning technique or surface treatment. Shou Sugi ban is never made from unstable timbers like pine or Siberian larch, reclaimed wood, or chemically treated wood.
You will only see excellent results from traditional Japanese fire conditioning using stable Japanese Cypress, results that will last over time. Yakisugi (Shou Sugi Ban ) cannot be replicated without the traditional drying and contained heat treatment process only found in Japan. It is not burned with a torch, kiln dried, made from tongue and groove profile, or burned after installation.
Yakisugi (Shou Sugi Ban ) or “shou sugi ban” as many mistakenly call it, are finished products, not a verb or adjective.
How is it made?
Historically, Yakisugi (Shou Sugi Ban ) has been made by the Japanese contractor on each jobsite. Only in the last several decades has Yakisugi (Shou Sugi Ban ) manufacturing transitioned to timber mills such as us due to the demands of Architects and needs of high consistent production of the construction market. In Japan a holistic and narrow manufacturing protocol has been developed over hundreds of years to ensure dimensional stability and maximum longevity, which we have studied replicated in New Zealand.
The Shou Sugi Ban process starts off in Japan with careful log selection, grading for straightness and diameter, grain density and quality, and wood color. The logs are sawn flat or quarter sawn, then the timber boards are air or sun dried. Shou Sugi Ban does not work well with kiln dried timber, as kiln drying creates an inferior product.
The fire conditioning is intense, and the wood is quenched at the perfect time. Then it is dried again so the timber is ready for the customer in the charred Sendai finish. Or the charred timber is then brushed to remove charred layer to reveal the textural beauty to achieve the desired appearance. Standard traditional products include Suyaki (original charred), Gendai (brushed once), and Pika-Pika (brushed twice).
How does the fire treatment work?
The Shou sugi ban heat treatment improves cladding longevity by preventing decay and insect infestation, makes the boards more dimensionally stable, and improves fire retardancy.
Wood is predominately made of structural lignin, with hemi-cellulose carbohydrates which are food for fungi and insects. Fire conditioning of Yakisugi (Shou Sugi Ban ) burns off the cellulose, removing the primary food type and minimizing rot and infestation. The fire conditioning treatment also case hardens the timber, and in combination with air drying, improves dimensional stability in severe weather exposure. The charred layer increases the temperature threshold needed for combustion, significantly reducing flame spread. The charred layer is also a natural hydrophobic protection against weathering.
Does the wood truly become a no-maintenance timber product?
In Japan the answer is yes. In New Zealand Yakisugi (Shou Sugi Ban ) is a very low maintenance timber cladding finish which only needsto be re-oiled every 7-10 years to slow down the weathering process.
All Yakisugi (Shou Sugi Ban ) surfaces start off with the boards being deeply heat treated to the charred finish of Suyaki.
From there we brush the boards to next to achieve the Gendai finish. The pike Pika-Pika finish is lightly burnt and brushed again. Suyaki’s thick soot layer will keep the same colour for up to 80 years depending on burn quality and site conditions. However, the Gendai and Pika-Pika brushed surfaces will weather over time and we advise a 3-5 year oiling cycle for a smart appearance.
With Yakisugi (shou sugi ban) we must differentiate between wood and colour longevity. While heat treatment preserves the wood, a re-oiling schedule is necessary to maintain colour. We recommend you live with your Yakisugi (shou Sugi Ban) for several years before considering re-oiling, given the chance you will enjoy how the product develops a rich patina with time — not to mention avoiding the unnecessary maintenance costs.
What makes the best Shou Sugi Ban?
Many timbers are excellent for charring, some are not suitable like Western Red Cedar as its char falls off very quickly. Siberian Larch, Californian Redwood, Lawson Cpyress, Thermally modified pine (Abodo, ThermoWood Accoya) and of course Japanese Cedar are all excellent timber for the process.
The ideal characteristics we look for are straight-grained, fast-drying, tannin-rich, stable and strong timber— very much all desirable characteristics for timber cladding. Most importantly a thick, dense latewood growth ring, which burns to a more substantial, longer-lasting char layer. Many timbers in teh cypress family have chemical properties that respond well to fire, and it becomes incredibly dimensionally stable when milled, dried, fire conditioned in the traditional Japanese way.
In Japan the largest forestry company who produces Yakisugi is Nakamoto forestry, and they will only use Japanese Cedar.
Our experience has shown that hardwoods promise greater longevity, but do not live up to the environmental standards of Yakisugi (shou sugi ban) or fire well with the traditional process.
If you are looking at these alternatives, we stress that you must take the long-term perspective. We trust our cladding to look great without any maintenance for its lifetime in New Zealand. Chemically treated wood, hardwoods, or faux finishes will always weather inconsistently and do not have the in-service history to prove their durability or performance over time.