How Long Does Charred Wood (Shou Sugi Ban) Last?
Surface charred wood (also known as Shou Sugi Ban) has become an international sensation. However all charred timber is not created equal.
Surface charred wood - an ancient Japanese technique known as Shou Sugi Ban - has become an international sensation with articles in the New York Times and our overflowing social media feeds; taking things to a fever pitch.
However, not all charred timber is created equal. In the rush to char wood, it is safe to say shortcuts have been taken and there are misunderstandings about charred timber, in particular regarding its lifespan.
Firstly, the choice of timber is critical. Open celled timbers work best, as during the charring process the outermost cellulose burns off, which leaves blackened lignin behind. Depending on the level of char, this can create a charred alligator type skin on the wood. The ancient Japanese process has typically used Sugi (cryptomeria japonica); a soft, naturally durable timber native to Japan.
For this reason softer, stable naturally durable timbers work best. It is critical that a minimum 2-3mm of char is created in order to create a “wear layer” when the wood is exposed to weather.
Beware of charred hardwood, as the majority of hardwoods do not achieve the depth of char required to provide long lasting durability.
Abodo’s Vulcan timber is a perfect substrate for charring. It’s a softer naturally durable timber, without the knots found in Japanese Sugi. It also carries Forest Stewardship Council® (FSC®) certification for sustainability.
Secondly, char depth is also critical. A heavy char will last longer than a light char. When exposed to rain and UV, wood slowly erodes, and it is this sacrificial char layer that erodes. The thicker the char layer, the longer the black char colour lasts, along with its preservative benefits in protecting the timber.
In Australia, much of the charred timber on the market is hardwood, which is not ideal due to the lack of char depth and consistency. In these cases the desired outcomes will fall short. Abodo uses proprietary oils to create a harder char layer, which in turn reduces flaking of the coating, and improves durability of the char layer.
Brushing the charred wood often creates a beautiful appearance which can be finished with a natural oil. This finish is more suited to interiors, and will quickly weather if exposed in an exterior environment.
So, how long will a properly charred timber last, when exposed to the full ravages of weather? It is most certain that it will outlast all black semi transparent oils and stains. But the truth is no-one really knows.
Abodo testing has indicated that a 2mm char will last for 5 years at minimum, in a fully exposed application. Regular coating of Char Oil will help maintain the surface char, and colour integrity ongoing.
Due to the variability of factors associated in the process there is certain to be mixed results. However the process has a long lifespan, with Japanese examples of Shou Sugi Ban lasting for well over 50 years.
At Abodo we believe quality long lasting finishes are a part of a sustainable future, which is why we believe in thorough testing before market launch, and also continually revisiting completed projects. A quality supplier should always have projects several years old to prove durability and quality.
At Abodo, we’re on a mission for alternatives to what has long been considered normal. Our vision is for all timbers to be safe, sustainable and cared for, like the forests they come from.
Our thermal modification process drives resins from wood and increases the timber’s stability, so it is able to take dark finishes.
This also means our timbers have exceptional weatherability, they’re low maintenance, and maintain their durability and beauty for a lifetime.