Shou Sugi Ban Is Chemical Free, Easier on the Planet

Traditionally, shou sugi ban is performed on cedar - sugi is the Japanese word for cedar. The process of shou sugi ban, done by hand, involves several steps. First, the wood is blackened or charred using fire. Then, it is cooled, and any soot or burnt debris is brushed off the surface. The boards are then finished with oil. Fire is often considered a destructive force when it comes to wood. Interestingly, it's the damage done during the charring process that makes shou sugi ban a sound and sustainable choice for buildings. 

Here's why. The charring process works at the cellular level, creating a carbon layer on the wood's surface. The char protects the interior wood like a stain or sealant. Shou sugi ban thus enhances wood's durability. It's a natural way to preserve wood without chemicals, paints, or other surface treatments. The carbonized wood is also waterproof. 

There's more, adds Jonathan Orpin, founder, and owner of Pioneer Millworks, a reclaimed and sustainable wood products company that also produces shou sugi ban. "In addition to putting a protective coating on the wood to minimize UV degradation," Orpin says, charring protects against insects, bacteria, and mold. "Functionally, shou sugi ban chars their dinner. We burn the front and back of our boards for these reasons." Here's a video on Pioneer Millworks' shou sugi ban process. 

Aside from the gas used during the charring process, shou sugi ban is environmentally friendly. There are few to zero chemicals present in the process and the resulting product. Moreover, shou sugi ban is wood, adds Orpin. "Is there any renewable resource with a lower carbon footprint than wood? Or with a higher embodied carbon? Wood rocks!" 

Charmed by Char

For the Musichs, "Both the look of shou sugi ban and the artisanal ethic of the process suited the project and the clients," McGuire says.

"They were up for doing much of the finish carpentry work themselves and for putting in the elbow grease to get long-lasting results," she adds. "There's something fun about the exterior of the sauna (traditionally a building heated by burning wood) having a charred exterior. And, let's be honest: Who doesn't like playing with fire?" 

Over several weekends, with help from numerous friends, the Musichs placed hundreds of 1 x 6 cedar boards milled into a shiplap profile on concrete blocks. (You can also use metal sawhorses, McGuire suggests.) 

Using a propane-fueled weed burner, they made two passes along each plank—just to the point at which they'd achieved alligator-scale-like texture. The couple then used a brush with hard bristles to remove the ash. They finished the boards with tung oil, "which is a little bit processed, but not as toxic as many other substances," McGuire says. Here's a video of the Musichs at work.

The 10-by-12 sauna used about 350 square feet of shou sugi ban siding, McGuire adds. "In a world of over-processed products with lots of toxic mystery ingredients, shou sugi ban is a straightforward solution," McGuire says. 

"People, especially do-it-yourselfers, take comfort in that," she continues. "For many reasons, shou sugi ban remains popular in Japan—because it adds fire, rot and insect resistance to wood, and has the ability to weather beautifully. Those reasons, combined with its DIY opportunities and sustainability aspects, make shou sugi ban an option full of potential, particularly for cabins and outbuildings."