How Long Does Shou Sugi Ban Last?

Customers often ask us how long shou sugi ban will last. 80 years is commonly seen on the internet but I am not sure where that specific number came from.  I’ve traveled throughout Japan studying traditional siding design and weathering. Shou sugi ban siding will last at least that long, longer if regularly maintained. But it’s important to define what it means for siding to “last”. Does it mean to keep weather out or does it mean to stay the original color? Also it’s super important to understand that design, installation, and maintenance all affect how long shou sugi ban will last.

Keeping Weather Out

Functionally, siding simply needs to keep water and sun off of the underlayment. For durability it’s also beneficial if bugs aren’t attracted to it, fungus doesn’t grow on it, and if it’s easy to maintain.  So functionally siding will end its lifespan when it splits into pieces, twists dramatically, gets bug-eaten, or rots.  Then it won’t keep the weather out and should be replaced.

What I’ve seen in Japan is that shou sugi ban generally reaches its lifespan when the planks erode so thin from weather that they eventually fall apart. The gradual process takes around 100 years but this depends on conditions.

The protective soot washes off after a few decades and it’s rarely recoated with oil to slow down weathering.  Sun exposure breaks down the wood fibers on the surface, and then rain and wind wash them off. The next layer of wood fibers is exposed and the cycle continues. If the building is still standing when the siding reaches its lifespan, the shou sugi ban is simply replaced.

Changing in Appearance

Ideally siding should also look good while protecting the building from weather. All wood siding  including shou sugi ban will change color as it weathers and needs reoiling to stay looking the same. Shou sugi ban certainly will not stay black 100 years without maintenance as many people assume. The soot or oil will erode off eventually and expose the brown wood underneath.

Exposed wood generally turns reddish brown when facing south and gray when facing north. It changes evenly in some areas and patchily in other areas. UV radiation turns the wood reddish brown. It fades tan then gray the wetter it gets, and turns black from acidic rain or mildew. Since it is rarely re-oiled, shou sugi ban is called an organic, living, or patina siding material.

Much modern architecture assumes that wood siding should stay the same color as long as possible. Paint gives 100% UV protection so stays the same color for about 25 years before peeling off. Oils give UV protection 90-99% so the wood color underneath fades more quickly than paint. Also oils wash off gradually over a number of years including the pigment, adding to the fading effect. So oils match the shou sugi ban weathering aesthetic better than paints.

Factors That Affect How Long Shou Sugi Ban Lasts

Design and material

The most important design element in terms of how long the shou sugi ban will last is how big the roof overhangs are. If you go with a Northern European roof line without eaves, then the siding will weather quickly. If your design has Craftsman-style 24” or larger overhangs, then the siding will last longer since it’s more protected from sun, wind and rain.

Installation and maintenance

This is the most important factor in how long your siding will last. Siding needs to be installed thoughtfully so it dries out quickly and stays flat on the walls.

John of Sunshine Construction showing us the details of his Passive House design
Learn everything you need to know about proper shou sugi ban installation here.

Maintenance

The more maintenance you do, the longer your siding will last. “Maintenance” generally means re-coating periodically with a fresh coat of oil. It can also mean using a hammer to tighten up nails that work their way out from temperature and moisture cycles.

Watch more shou sugi ban maintenance tips, case studies and more on our YouTube channel!

Local Conditions

You can use shou sugi ban anywhere in the world. But it will weather differently depending on exact site conditions. Customers in northern regions are generally the most concerned with how well shou sugi ban will perform in their area. But in my experience the colder climates simply preserve the wood longer. The most challenging climates for wood siding are the arid desert where the dryness causes the boards to cup, and the humid southeast where humidity causes the boards to rot.

Shou sugi ban is a traditional Japanese siding where the color and texture changes are enjoyed according to the wabi-sabi aesthetic. I think measuring how long it lasts is therefore a functional exercise.  So shou sugi ban will last at least 100 years.

Age estimate: 40-80 years old; note rot from direct masonry contact, also color difference between high-UV load center of wall and silvering at the bottom from moisture, also flat-sawn resaw pattern.
historic yakisugi example 100-150yrs
Age estimate: 100-150 years; note wood thickness erosion and checking, masonry contact, also 30-40 year-old Suyaki™ patches.
historic yakisugi siding
Age estimate: 30-60 years; note quarter-sawing, uncoated traditional cut nails, ferrous streaking, nails backing out, wood erosion making the nails proud.
Age estimate: 80-120 years; note intact soot layer directly under the water table (between stucco above and wooden wainscotting), ferrous streaking, 4 nails per board, Suyaki™ erodes to a Gendai™ appearance over time, wall is likely north-facing, knots indicate rootstock down and crown up, flatsawn from young trees.
historic yakisugi showcasing shou sugi ban durability depending on orientation
Age estimate: 5-15 years; note silvering left side from daily exposure to an adjacent river’s morning dew, right side warm wood color from high UV load.
historic shou sugi ban
Age estimate: 80-120 years; note short, thin, low-grade planks indicating low budget, square butt joints, also whitewashed mud wall with straw reinforcement and bamboo lathe.
historic yakisugi showcasing shou sugi ban durability after a century
Age estimate: 80-120 years; note overlap bond line between upper and lower stories, cupping and missing board due to using headless nails, traditional mud wall and horizontal nailers between posts.

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