Japanese Burnt Wood Siding: Top 10 Myths About Yakisugi “Shou Sugi Ban”

Over the years, we’ve seen a lot of mixed information circling the web surrounding what yakisugi “shou sugi ban” siding is, how it is used, and even about wood siding in general. As the industry leader for over 50 years, we feel it’s our responsibility to set the record straight with some facts.

So, let’s dig in and debunk some commonly heard myths, misconceptions, and marketing claims about burnt wood siding and how to select authentic Japanese yakisugi “shou sugi ban” products for your projects:

Myth #1 – Yakisugi siding is expensive.

Yakisugi is a vernacular building material that maximizes millwork tradecraft, so making it is more knowledge-based than expense-based. That means it should have good value compared to other cladding options and a vendor’s high cost might more reflect custom millwork, high overhead, or pricing strategy. The Japanese heat treatment process does not add that much production cost to the wood product, and yakisugi should not be much more expensive (if at all) when compared to other stain-grade wood siding options.

Also, when lifetime durability and the need for little-to-no maintenance is taken into account, yakisugi’s long term cost performance is fantastic. As such, affordability has always been associated with yakisugi siding in Japan.

Myth #2 – Regionally sourced wood has a lower carbon footprint and costs less.

It’s a common false assumption and “greenwashing” claim that regionally sourced siding products automatically offer lower costs and carbon footprint.

Today’s building material supply chain is diverse and driven by economics. Lumber is sold on an international market and can be efficiently transported. Ocean freight has a much lower carbon footprint than regional trucking or even transcontinental rail freight in terms of pounds moved per mile (ratio is ocean = 1, trucking = 7.1, rail = 4.9). Case-by-case, either local or non-local materials can have both a lower cost and a lower carbon footprint. Yakisugi siding offers the additional advantage that finished products are naturally more efficient to ship than raw materials.

Myth #3 – Many wood species work for making yakisugi.

Virtually any species of wood can be burned to make siding—but the results will certainly vary by degree in terms of product performance and aesthetic appearance. In Japan, only sugi cedar (Cryptomeria japonica) is used for making authentic yakisugi products. Since yakisugi is primarily used for exterior siding applications, it must be dimensionally stable throughout all seasons, provide long-term durability exposed to various climates, deliver good cost performance—not to mention offering an unparalleled aesthetic beauty and design versatility. A few technical facts about why sugi cedar is the singular material choice for this product:

• Hard or dense wood species will often twist, cup, and/or split over the long term when it’s burned at a high temperature and then exposed to exterior weather conditions.
• As a light and porous softwood, sugi works exceptionally well for deep heat treatment penetration, dimensional stability, and fast drying times in wet weather.
• Sugi cedar’s thick latewood growth rings turn into a solid, longer-lasting protective soot layer after burning.
• The wood offers beautiful grain patterns and color variations, which naturally become exposed as yakisugi weathers over time or if the soot layer is wire-brushed before installation.
• Sugi’s tannins, mineral content, and essential oils (not resin) are all natural biocides that help prevent rot and repel insects.

Myth #4 – You can choose differing levels of yakisugi char.

Can you order “Medium Rare” or “Well Done”? Not if it’s real yakisugi. All authentic yakisugi products are deeply charred to heat treat the wood. After burning, different surface treatments can be used to achieve varied appearance. The sooty, textured surface can be left alone for protection and character (Suyaki), it can be brushed lightly for a smooth and more refined appearance (Gendai), or it can be wire-brushed to show more of the grain texture and color (Pika-Pika).

Cosmetic shallow or “light” burning (such as aburi—see Myth #9 below) only carbonizes the less dense earlywood growth rings, but not the dense latewood. “Deep” shou sugi ban heat treatment followed by wire brushing leaves latewood growth rings carbonized and black, and the blonde and red earlywood growth rings can be exposed by brushing off the soft soot. This is our Pika-Pika product.

If you know what to look for it is easy to tell the difference between shou sugi ban and “faux” sugi ban (i.e. aburi labeled shou sugi ban) since the striped grain patterns are negative images of each other. It is confusing and counterproductive to use the words “shallow” or “light” as burning options since that is a faux finish for interior applications, not for heat treated exterior shou sugi ban.

Myth #5 – Tongue-and-groove is necessary for vertical yakisugi applications.

Some people believe that a tongue-and-groove (T&G) profile works best for vertical siding installations because: 1) it keeps water out, and 2) it can be blind nailed for the sake of appearance.

Exterior siding is meant to shed water and protect the vapor barrier from UV degradation, not to be waterproof. Water will always get behind siding and dry time equates to siding longevity, so it is critical that the cladding weeps and dries quickly. Because T&G profiles create more water tension at the joint, it weeps and dries slower than shiplap or square planks.

T&G was not used for exterior siding until after WWII, when the construction boom targeted a low price-point and traditional millwork know-how was left by the wayside. The precision millwork and intensive heat treatment process used to manufacture authentic yakisugi produces a dimensionally stable material, so a locking-type T&G pattern is not necessary. Additionally, the square edges on T&G (or channel lap) will melt if thoroughly burnt and the resulting wavy parallel lines simply do not look good.

Blind nailing is also not recommended for exterior wood applications since hidden fasteners cannot be tightened during future maintenance. The wood will always move over time due to moisture fluctuation and latent instability in the planks. Face-nailed siding will move less and look better over time since headed fasteners have higher strength and can be easily tightened up periodically with a hammer. Also, yakisugi is by nature a thin-stock material—too thin for hidden fasteners.

Myth #6 – Yakisugi must be installed by experienced carpenters, which means higher labor costs.

Yakisugi is simply wood siding, installed with the same carpentry skillset as any other wood siding product. Unbrushed yakisugi will slow the installers down to some degree since it is delicate and must be handled carefully, however brushed yakisugi products typically install faster than most other wood siding options. This is due to shiplap or square edge boards laying out with less effort than tongue-and-groove siding. In addition, the precise millwork and heat treatment process makes yakisugi boards straighter than most kiln dried lumber.

We recommend working with a known conscientious contractor; there is no need to seek out someone with specific experience installing yakisugi siding.

Myth #7 – Mesh or Drain Wrap is an Acceptable Underlayment Instead of Furring Strips

This myth is related to all siding—not just yakisugi. Mesh or drain wraps can allow enough air flow between the siding and water-resistant barrier, but they do not offer a rigid structure under the siding. Therefore, they will not keep the siding in a flat plane as a standalone underlayment. Mesh can be used for venting under horizontal rigid furring when the siding is installed vertically. But to keep the wall plane flat over the long term, the siding planks must be held between fasteners acting as clamps and a rigid furring bed acting as a flat anvil.

Myth #8 – Yakisugi will stay black and will last up to 80 years.

Unbrushed shou sugi ban will remain black for about 50 years due to the carbonized soot layer. But if the soot is brushed off during the manufacturing process, it will be brown and weather in color just like any other stain grade wood siding. As a basic premise, yakisugi is designed not to ever need an oil finish. To help preserve the original color of a brushed or unbrushed yakisugi product, an oil finish can be reapplied as maintenance every several years (just like any other wood siding).

Yakisugi can last at least 80-120 years without maintenance and even longer if re-oiled. The durability limitation is that ultraviolet radiation will degrade the surface wood fibers over time and the planks will get thinner and thinner due to erosion. Eventually the siding splits out and falls apart. Re-oiling maintenance can slow down the weathering process since pigments in many finishes offer UV protection and the oil moisturizes the wood. When the wood reaches its lifespan it is simply replaced.

Myth #9 – The process of burning wood is called yakisugi

Yakisugi “shou sugi ban” is a product, not a process. To make yakisugi, thin-stock Japanese cedar planks receive an intensive flame treatment; the charred wood is then primarily used for exterior siding. But there are many other instances where heat is applied wood for various purposes and effects used worldwide:

“Aburi” refers to a cosmetic burning treatment done by torch to create a darker surface appearance. This technique may be applied to different wood species and applications, such as on furniture or for interior millwork like exposed beams.

Thermally modified wood is a low temperature process that penetrates more deeply into the wood and can be used on thick stock for improved durability in exterior applications. This technique is popular among manufacturers in many Nordic and Baltic countries.

In China, manufacturers use a high-temperature carbonization process to harden wood for things like flooring products.

Yakisugi siding is made to last as long as possible under challenging exterior conditions and therefore it is a form-follows-function material. For optimal durability, stability, and fire-resistance, carefully selected Japanese sugi cedar (Cryptomeria japonica) logs undergo precision milling followed by a high-temperature charring process.

A handheld torch cannot be used to make true yakisugi because it does not have sufficient BTU energy to burn off enough hemi-cellulose in the wood. A traditional triangular or quadrangular flue, or modern hotbox method, should be used to apply enough energy to the wood for thorough treatment. In addition, only thin plank wood dimensions will stay straight through the charring process due to moisture content fluctuation. This manufacturing process will also melt both edges of tongue-and-groove, fineline, or channel lap profiles; therefore, only shiplap and square edge plank profiles should be used to make yakisugi.

Myth #10 – In Japan, charred siding is called “shou sugi ban”

The word for traditional charred siding in Japan is yakisugi. The term “shou sugi ban” doesn’t naturally exist in Japanese. This name only originates from around the year 2000 because of a Westerner’s misreading of the written Japanese word for yakisugi. People outside of Japan often use shou sugi ban instead of yakisugi—either because they don’t know better or in deference to keyword metrics for search engine optimization (i.e., Google search results).