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Shou Sugi Ban: The art of charred timber

The timeless tradition of Yaki Sugi

Shou Sugi Ban, or Yaki Sugi, is a traditional Japanese technique of preserving wood by charring its surface. This ancient method, with a history stretching back centuries, is now finding new life in modern architecture and design, particularly in the UK.

Originating in 18th century Japan, Shou Sugi Ban was initially developed as a practical solution for weatherproofing timber siding against harsh conditions.

The process involved charring the surface of the wood, then cooling, cleaning, and finishing it with natural oils. This method enhanced the wood’s resistance to elements and gave it a distinct, aesthetically pleasing appearance.

Yaki Sugi (Shou Sugi Ban) produces a dark and vibrant aesthetic.The technique

Shou Sugi Ban’s process involves charring the wood’s surface to create a carbon layer. This protective shield layer makes the wood resistant to rot, pests, and fire. The depth of the charring can vary, resulting in different textures and hues, from deep blacks to silvery greys.

In the UK, there’s a growing appreciation for Shou Sugi Ban, especially in the context of sustainable and durable building materials. Companies like Brighton Bike Sheds have adopted this technique, recognising its unique blend of functionality and beauty.

 

Charring Scottish larchEach of the sheds within our portfolio can benefit from the charring process of yaki sugi.

We use Scottish Larch with our charring process for a variety of reasons, including;

1. Durability and Resilience: Scottish Larch is renowned for its natural durability. Its high resin content makes it naturally resistant to rot, decay, and pests. This resilience is further enhanced with the Shou Sugi Ban technique, making it ideal for outdoor applications such as bike sheds, garden structures, and exterior cladding.
2. Local Sourcing and Sustainability: Sourcing Larch locally from Scotland reduces the carbon footprint associated with transportation, aligning with eco-friendly practices. This is particularly important in sustainable building practices, as it supports local economies and reduces the environmental impact of importing materials.
3. Aesthetic Qualities: Scottish Larch has a distinct grain pattern and colouration that the charring process can enhance. The textures and hues achieved through Shou Sugi Ban can range from deep, rich blacks to silvery greys, providing a unique and visually appealing finish that complements various architectural styles.
4. Weathering Properties: Scottish Larch’s ability to withstand different weather conditions is crucial in the UK’s varied climate. The Shou Sugi Ban treatment further augments its weather resistance, making it an excellent choice for damp and changeable weather in the UK.
5. Dimensional Stability: Larch is known for its dimensional stability, meaning it is less likely to warp or change shape due to moisture changes. This is particularly important for structures like bike sheds, bin stores and associated storage products, where maintaining shape and form over time is essential.
6. Adaptability and Versatility: The wood is adaptable to various designs and finishes, allowing for creative and flexible use in various products. It can be used in traditional and contemporary designs, making it a versatile choice for different architectural styles.

Char your Bike Shed

Common Yaki Sugi FAQs

Please see a selection of the most commonly asked questions relating to the charring of our timbers.

Is Shou Sugi Ban fireproof?

The risk of fire was a very real concern for house builders in 18th century Japan. And it may seem counter-intuitive but the charring process of Shou Sugi Ban significantly enhances the fire resistance of the treated timber, without making it completely fireproof. The carbonised layer on the wood’s surface acts as a barrier to reduce flammability. This charred layer slows down the ignition and burning rate of the wood by removing some of the volatile compounds that fuel combustion. Additionally, charred wood tends to release less heat when it does burn, which can help slow the spread of a fire.

However, the degree of fire resistance afforded by Shou Sugi Ban varies depending on the extent of the charring and the type of wood used. While it provides enhanced fire resistance, it should not be solely relied upon as a fireproofing method. Shou Sugi Ban-treated wood can be part of a comprehensive fire mitigation strategy in construction. Still, adherence to local building codes and implementing multiple fire prevention and protection measures are essential for safety.

What is the difference between thermally modified wood and Shou Sugi Ban?

Thermally Modified Wood (TMW) and Shou Sugi Ban are both methods used to enhance the properties of wood, but they employ different processes and yield distinct results:

Thermally Modified Wood (TMW)

1. Process: TMW involves heating wood to high temperatures (usually 160 to 215 degrees Celsius) in a controlled environment with low oxygen. The process can take several hours and is done in specialised kilns.
2. Chemical Changes: The high heat alters the wood’s cell structure and chemical composition. This reduces the amount of hemicellulose, a type of sugar in wood that is prone to decay and water absorption.
3. Properties: TMW becomes more resistant to rot and decay, has reduced moisture absorption, and is less prone to warping and swelling. This makes it suitable for outdoor use without the need for chemical preservatives.
4. Aesthetics: The heat treatment darkens the wood uniformly, giving it a rich, homogenised colour. However, it doesn’t create the same textured, charred surface as Shou Sugi Ban.
5. Applications: TMW is often used in outdoor applications like decking, cladding, and outdoor furniture, as well as in humid environments like saunas.

Shou Sugi Ban

1. Process: Shou Sugi Ban involves charring the surface of the wood with an open flame. The charred layer is then cooled, cleaned, and sometimes finished with natural oils.
2. Chemical Changes: The charring process carbonises the surface of the wood. This carbon layer acts as a protective barrier but does not significantly alter the wood’s chemical composition.
3. Properties: The charred surface increases rot, decay, and pest resistance. It also offers some level of fire resistance, unlike TMW.
4. Aesthetics: Shou Sugi Ban is known for its distinct, visually striking appearance. The charring process creates a unique texture and colour variation, ranging from deep black to silvery grey, depending on the degree of burning and brushing.
5. Applications: Traditionally used in Japanese architecture, it’s now popular worldwide for siding, fencing, and decorative purposes where aesthetics are a priority.

In summary, while TMW and Shou Sugi Ban enhance the durability and longevity of wood, they differ in their processes, the extent of chemical modification, their resultant properties, and aesthetic outcomes. TMW involves more thoroughly altering the wood’s properties through heat treatment in a low-oxygen environment. At the same time, Shou Sugi Ban focuses on surface modification through charring, offering unique textures and aesthetic qualities.

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