Suyaki

For the exterior scope of your project, we would recommend either unoiled Suyaki or Suyaki with a tung oil finish. For the interior portions, please separately specify Suyaki with a polyurethane coating. A clear distinction in specifications ensures that each product is optimized for its designated application in support of superior performance and customer satisfaction.

We carefully specify the suitability of our products for interiors, exteriors, or both. Exterior-only products are exclusively designed for outdoor use and should never be used indoors. Interior-only products are intended for indoor applications and should not be utilized outdoors.

The short answer is yes. Our Suyaki product is designed to offer the longest lifespan; unbrushed soot layer can remain intact for 30-50 years without any maintenance. 

Despite its resilience, Suyaki will inevitably develop blemishes through handling and exposure; this is a natural characteristic of this traditional material. Over the years, the soot layer may be scratched, abraded, and gradually eroded, revealing the brown wood beneath. It can be rejuvenated with touch-ups and recoating using black oil, maintaining the timeless wabi-sabi aesthetic. 

As the Suyaki soot layer weathers, the exposed wood beneath begins to resemble our single-brushed Gendai products. Over time, it will transition to look more like our twice-brushed Pika-Pika products.

The Suyaki surface is delicate and susceptible to damage during transport and installation. Although installation follows standard wood siding procedures, extra care should be taken when handling the boards to minimize potential damage. To address any blemishes, we recommend utilizing the black oil provided with each wood shipment for touch-ups.

Suyaki installation labor may increase by approximately 10% compared to our other wood products due to the need for careful handling.

For those with concerns about using Suyaki, we suggest opting for one of our brushed surface products (Gendai or Pika-Pika) or securing an installer experienced in working with Suyaki.

Suyaki with an exterior-grade tung oil finish is not suitable for indoor applications. For interior applications, Suyaki requires multiple heavy coats of polyurethane to stabilize the delicate soot surface. By their nature, most polyurethanes become glossier with thicker applications. Unfortunately, all of the matte-sheen polyurethanes we’ve tested have proven to be dull and uninteresting on our Suyaki product. 

If you desire interior paneling with a less glossy appearance, we recommend specifying Gendai or Pika-Pika with a black alkyd or acrylic coating.

In most cases, our interior and exterior coatings should not be used interchangeably. The heavy polyurethane coating applied to Suyaki for interior applications is specifically formulated for its intended environment; it is not suitable for exterior applications. When exposed to the typical UV and moisture of an exterior siding installation, a polyurethane coating will start to degrade. Even the most durable hard shell polyurethane coatings will eventually exhibit issues such as turning milky white, yellowing, cracking, and/or peeling.  

While options like marine-type varnishes offer some of the toughest exterior coatings available, these finishes are designed to be periodically scraped off and reapplied on a regular maintenance schedule. This simply could be done with yakisugi products due to the nature of the material. 

A heavy polyurethane coating lacks the elasticity needed to enhance the natural resilience of yakisugi against ever-changing exterior conditions. Even worse, it would significantly reduce the expected lifespan of a 100-year siding material—potentially limiting it to just five years. 

Please specify one of our products designed for exterior applications instead.

Protecting the delicate soot layer on our Suyaki products requires careful manufacturing and packing processes. This additional labor slightly raises the production costs for Suyaki versus our Gendai products.