A lot of Westerners considering traditional yakisugi, shou sugi ban or any kind of charred wood siding start with the assumption that because it is burned, it will be black and stay black forever without any re-oiling maintenance. This comes from confusion between wood durability and color longevity, probably originating from the repainting cultural tradition that exists in most of Europe. One of charred wood siding’s most desirable characteristics is the nuanced color and organic patina. In a previous blog I discussed the difference between wood longevity and color longevity. In this post I want to focus on how wood color changes on exteriors based on several different environmental factors.
Wall orientation, local climate in terms of UV and moisture exposure, the roof overhang and wall height, the product and finish type, and also the pigment color all affect color change. When selecting siding, keep these things in mind to plan for color change in any type of siding accordingly.
Siding Orientation and Local Climate
Walls that get more sun will tend to mellow reddish brown since the wood oxidizes and develops rich color. This is generally the SE, S, and SW orientations.
Walls that get more moisture and less sun will tend to fade and bleach to gray over time. This is generally the NW, N, and NE orientations.
Old pioneer siding and fencing out West and barns in the Midwest are typically brown on the south elevations and gray on the north elevations. As such, reclaimed wood is generally sold as brown or gray since wood naturally weathers to these colors.
Interestingly, yakisugi exposed to both sun and rain will often appear reddish brown when wet and gray when dry. Where our distribution is located in Oregon this means West elevations due to the prevailing westerlies carrying moisture off the Pacific.
Structures located near the ocean and exposed to abrasive coastal weather generally means more moisture in the environment. This causes the entire structure to fade gray over time. This effect is where the Cape Cod gray or Sea Ranch silver palettes come from.
A lot of modern house designs have European influence which often means short rafter tails or none at all. A large overhang vs a minimal overhang will affect siding weathering dramatically. If there is a large overhang then the siding directly below it will stay the original color much longer. Lower wall sections will develop patina due to exposure. A roof line without overhang will be fully exposed top to bottom, and will therefore weather more quickly and evenly.
Charred Wood Siding Properties
With a soot layer or pigmented finish acting as a protective coating, over time the patina color can be seen where the coating wears off and exposes the wood grain. This generally means brown or silver show up on areas of damaged Suyaki within a few years. Also latewood growth rings on Gendai and Pika-Pika are more dense and therefore the oil finish won’t soak in due to density so dried in a thin layer on the surface.
Oil Finish Formula, Pigment Load and Pigment Color on Wood Siding
Most mills in North America use solid stains to meet the common western painted wood color longevity expectation. This also helps to make the colors stark and simple. Solid stains leave a thin layer of highly-pigmented oil finish on the surface, which blocks UV and preserves color. Semi-transparent oil finishes show depth of grain, color, and patina better, but will fade faster due to less UV protection. So basically it is a trade off between beauty and color longevity.
Solid stains also hide poor quality lumber or millwork, especially species that don’t have a defined grain pattern or are mostly blonde in color. With a western customer base expecting the longevity of painted wood and without a solid yakisugi millwork tradition, solid stains are much easier to sell. At Nakamoto Forestry we have the millwork figured out, so we have the luxury of focusing on semi-transparent stains. It is therefore important to set customer expectations.
To conclude, In our experience black, gray, and white oil finishes stay the original color longest. Natural, amber, and brown oil finishes tend to fade the first several months after installation before stabilizing a couple of tones lighter. When selecting a charred wood siding option for your next project, be sure to keep all of the factors we covered above in mind to ensure you get exactly what you want out of the lifetime of your wood!