The Japanese can build 4-5 story buildings using wood without the fear of fire for this reason.
As society develops, materials like concrete and steel are increasingly used in construction due to their sustainability and modernity. However, there is one country that has consistently used wood as a defining cultural feature throughout history: Japan.
Anyone who has visited Japan knows that there are very few high-rise buildings in this nation. Moreover, homes here are typically made of wood. Even today, despite advancements in construction technology, the majority of single-family homes in Japan, excluding apartments or other complex housing, are still built with wood. Why is this the case?
When thinking of Japan, we immediately envision the traditional houses built in the Wagoya style, characterized by pillars and beams primarily made of wood and other natural materials such as paper, straw, or clay.
Houses in Japan are often constructed from wood, yet they are effectively fire-resistant due to their unique materials. (Photo: Getty).
The use of natural materials in constructing homes helps the Japanese adapt to harsh natural environments, but it comes with a significant drawback: they are easily destroyed if a fire breaks out.
To address this issue, in the early 1970s, the Japanese developed a new fire-resistant material that retains the properties of wood. Essentially, they combined wood and steel to create a material similar to glulam (glued laminated timber), resulting in a strong connection surrounded by a steel frame.
When glulam is exposed to high temperatures, the surface of this material may catch fire. However, at the same time, a layer of charcoal forms, acting as a fire-resistant coating and providing thermal insulation.
This arrangement allows the material to effectively prevent the temperature within the steel frame from increasing. As the flames gradually cool due to being surrounded by fire-resistant materials, the glulam component will smolder without breaking the bond, ensuring the structure of the house remains intact.
When exposed to flames, a layer of charcoal forms on the material, providing a fire-resistant coating and thermal insulation. (Photo: Kenken).
Number of fire incidents recorded in Osaka from 1950-2020. (Data: DMA).
In fact, the principle of construction based on glulam is believed to have originated as early as the 1860s. The first patent for this material appeared in 1901 when Otto Karl Freidrich Hetzer, a carpenter from Weimar, Germany, discovered how to use multiple layers of wood and steel framing, bonding them together to enhance strength.
The effectiveness of this material has been confirmed following numerous experimental fires conducted by local authorities. Based on this, the concept of Hybrid Timber was established in Japan, and it was incorporated into the amended Building Standards Law in 2000.
Since then, the Japanese have been able to use structural components made from Hybrid Timber to construct 4-5 story buildings such as residential areas, office buildings, and commercial complexes.
The advantages of building with wood include its excellent thermal insulation and moisture absorption properties, making it ideal for the high humidity climate of Japan. Wood keeps homes warm in winter while remaining cool in summer. Regardless of the hot or cold weather outside, indoor temperatures are well-regulated.
In addition to using wood for construction, the Japanese also prefer this natural material for furniture, as it gives them a sense of closeness to nature. Moreover, the Japanese always value harmony with the environment, so natural light is optimized within their spaces.
However, the use of this material does come with some limitations and drawbacks.
Firstly, the properties of wood make it susceptible to changes in humidity, which can affect the durability of the structure. Additionally, the biological degradation of the material can occur anywhere.
According to estimates, in humid environments, the strength and bending capacity of Hybrid Timber can decrease by up to 43.5%.
