How to maintain Shou Sugi Ban charred timber for maximum durability!
Shou Sugi Ban – a traditional Japanese method of charring timber with fire – is a popular choice in residential and commercial buildings across Australia. The black timber cladding is known for its striking appearance and sustainable processes.
However, what really makes Shou Sugi Ban stand out is its durability and longevity, even when exposed to the harsh Australian climate. Like any building material, there are a number of things you can do to ensure your timber lasts longer.
At Mortlock Timber, we’ve spent years developing and refining our Shou Sugi Ban to bring you a beautiful and durable product. Here’s our expert advice on enhancing the durability of this beautiful product so you can enjoy it for longer.
What’s the science behind durability?
Although it may seem counterintuitive, the process of charring the timber actually makes it stronger and more durable. When performed by an expert, the Shou Sugi Ban process harnesses the properties of fire to enhance the wood’s properties.
Moisture trapped inside the wood is released and a black carbon layer is formed on the surface of the wood. Along with the oil coating, this carbon layer protects the wood from moisture and UV rays. It also acts as a repellent for termites, slugs and other insects.
The result is a resilient timber cladding that can be used in both interior and exterior applications.
How long does Shou Sugi Ban last?
When manufactured to a high standard, Shou Sugi Ban is highly durable. In fact, it tends to last longer than traditional non-charred oiled timber cladding options.
The reason why is because the carbon layer on the surface of the charred timber is thicker than normal timber coatings and oils.
The thicker the char layer the longer it lasts. Manufacturing is therefore a balance between charring the timber to maximize performance and not charring it too much which causes splitting and a surface that is too soft.
The timber species used and the environment where the cladding is installed can also affect its lifespan. Harsh weather elements such as sun and salt will speed up the aging process of any building material.
When timber is exposed to UV rays and rain, it begins to wear away, starting with the outer layer. However, with a thicker carbon layer, the timber is able to resist weathering for longer.
Does Shou Sugi Ban require regular maintenance?
Myth: Charred timber does not need any maintenance.
Reality: Any timber exposed to the weather will need maintenance at some point. The good news is that Shou Sugi Ban or charred timber does last longer without maintenance than non-charred timber.
Looking after your charred timber cladding involves recoating it with oil. How regularly you should apply an oil coating depends on the species of wood used.
Typically you should apply a new coating of oil every 2-4 years to preserve the structural and aesthetic integrity of the timber. For precise recommendations based on the timber species chosen, check out the timber species we discuss below.
Which timber species are best for charring?
The choice of timber is crucial for determining the level of durability. As manufacturers, we have rigorously tested this product before bringing it to market. Here is what we found.
Different timber species char differently depending on their density. Harder timbers like spotted gum take longer to char and have a thinner char layer. If you char spotted gum for too long the timber starts to warp.
Softer timbers like Burnt Ash char much quicker which means it has a thicker char layer.
However, timbers that are too soft – like pine and cedar – can char too quickly meaning they become brittle and the charred layer breaks off easily.
At Mortlock Timber, we offer three types of timber that can be used effectively for Shou Sugi Ban. These are Burnt Ash, Jarrah and Spotted Gum. Below we explain the advantages of each and how to care for them properly.
This maintenance guide below is for timber EXPOSED to the weather. If you wish to use Shou Sugi Ban in areas NOT exposed to the weather, maintenance oil coating is not normally required, only general cleaning and care is needed.
1. Burnt Ash
Burnt ash is thermally modified American White Ash. The thermal modification process increases the durability of American Ash which means it’s suitable for external use. Once thermally modified we call it Burnt Ash.
As Burnt Ash is extremely stable and has a medium-density it is the perfect timber for charring. It offers the right depth of char and requires the least amount of maintenance of our three options.
Burnt Ash cladding is supplied with a factory coat of oil prior to delivery. Once the cladding is installed, we recommend a second coat of oil is applied, and a third coat when the project is completed. The 2nd and 3rd coats need to be spaced 4-6 weeks apart to allow the oil to soak into the timber.
Whilst a maintenance coat is recommended every 3 years, Burnt Ash can last up to 5 years* without maintenance coats depending on the level of exposure to the weather and the location of the project.
Jarrah is a medium density timber that provides an excellent charred surface. Jarrah is a good all-around option as it offers great value for money and it also meets BAL 19 fire rating.
As Jarrah is not as stable as Burnt Ash the char layer is not quite as deep as Burnt Ash and does require extra maintenance.
Jarrah Shou Sugi Ban is supplied with a factory coat of oil prior to delivery. Once the cladding is installed, we recommend a second coat of oil is applied, and a third coat when the project is completed. The 2nd and 3rd coats need to be spaced 4-6 weeks apart to allow the oil to soak into the timber.
Whilst a maintenance coat is recommended every 2.5-3 years, Jarrah can last up to 4 years* without maintenance coats depending on the level of exposure to the weather and the location of the project.
3. Spotted Gum
Spotted Gum is a high-density timber which means the charred surface is not as deep as Jarrah or Burnt Ash. Spotted Gum is mainly used where the project requires BAL 29 timber cladding.
Spotted Gum Shou Sugi Ban is supplied with a factory coat of oil prior to delivery. Once the cladding is installed, we recommend a second coat of oil be applied, and a third coat when the project is completed. The 2nd and 3rd coats need to be spaced 4-6 weeks apart to allow the oil to soak into the timber.
Whilst a maintenance coat is recommended every 2.5-3 years, Spotted Gum can last up to 4 years* without maintenance coats depending on the level of exposure to the weather and the location of the project.
|Timber||Burnt Ash||Jarrah||Spotted Gum|
Density: 750 kg p/m2
BAL Rating: Non-BAL Compliant
Maintenance: recommended 3 years, can last up to 5 years.*
Density: 850 kg p/m2
BAL Rating: BAL 12.5 & 19
Maintenance: recommended 2.5 years, can last up to 4 years.*
Density: 1100 kg p/m2
BAL Rating: BAL 12.5, 19 & 29
Maintenance: recommended 2.5 years, can last up to 4 years.*
Note: Burnt Ash is not charred timber, Burnt Ash is the timber species name. Burnt Ash with Shou Sugi Ban finish is charred timber.
*The time between maintenance coats is a general indication, time will depend on exposure to the weather and location of your project. It could be more OR less time as we’ve seen it last longer in some instances and need more maintenance than listed here in other times.
Need advice for your next project? The specialists at Mortlock Timber are here to help.
We manufacture all of our charred timber in our factory. Over several years, we have refined our process to ensure a consistent and durable finish every time.
For enquiries about Shou Sugi Ban Australia wide, get in touch with our team of timber specialists today.
View our pricing and product guide
For in-depth information about the range of products we offer, please fill out the form below to download our Architectural Timber Pricing and Product Guide. Inside you will find illustrations, specifications, portfolio photo examples and a hardwood timber price guide to assist with budgeting.