The Japanese Can Build 4 to 5-Story Wooden Buildings Without Fear of Fire for This Reason.
As society develops, materials like concrete and steel are increasingly used in construction for their sustainability and modernity. However, there remains a country that has consistently utilized wood as a distinctive cultural feature for centuries—Japan.
Anyone who has visited Japan knows that there are very few high-rise buildings in this nation. Moreover, homes here are typically built from wood. Even today, with advancements in construction technology, the majority of single-family homes, excluding apartments or other complex housing developments in Japan, are still constructed using wood. Why is this the case?
When we think of Japan, we immediately envision an island nation with traditional houses designed in the Wagoya style, which includes structural elements like wooden pillars and beams, as well as natural materials such as paper, straw, and clay.
Japanese homes are commonly built with wood but are still fire-resistant due to the use of special materials. (Photo: Getty).
Utilizing natural materials in residential construction helps the Japanese adapt to harsh environmental conditions; however, it poses a significant risk of destruction if a fire occurs.
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 structure similar to glued laminated timber (glulam), resulting in a strong connection surrounded by a steel frame.
When glulam is exposed to high temperatures, its surface may catch fire. However, at the same time, a layer of charcoal forms, acting as a fire-retardant coating and providing insulation.
This arrangement effectively prevents the temperature within the steel frame from rising excessively. As the flames gradually subside due to being encased in fire-resistant materials, the glulam component will smolder without breaking its bonds, ensuring the structural integrity of the house.
When exposed to flames, a layer of charcoal forms on the material, serving as a fire-retardant and providing insulation. (Photo: Kenken).
Number of fires recorded in Osaka from 1950-2020. (Data: DMA).
In fact, the construction principle based on glulam is believed to date back to the 1860s. The first patent for this material appeared in 1901 when Otto Karl Freidrich Hetzer, a carpenter from Weimar, Germany, discovered the technique of using multiple layers of wood and steel frames glued together to enhance durability.
The effectiveness of this material has been confirmed after numerous fire tests conducted by local authorities. Based on this, the concept of Hybrid Timber emerged in Japan and was incorporated into the amended Building Standard Law in 2000.
Since then, the Japanese have been able to use structural components made from Hybrid Timber to construct 4 to 5-story buildings such as residential areas, office buildings, and commercial spaces.
The advantages of building with wood include its excellent insulation and moisture-absorbing properties, making it well-suited for Japan’s humid climate. Wood keeps homes warm in winter while remaining cool in summer. Regardless of how hot or cold it is outside, the indoor temperature can be well-regulated.
In addition to using wood for construction, the Japanese also favor this natural material for furniture, as it provides a sense of closeness to the natural world. Furthermore, the Japanese culture emphasizes harmony with nature, which is why natural light is optimally integrated into living spaces.
However, using 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 structures. Additionally, the biological degradation of the material can occur anywhere.
Estimates suggest that in a humid environment, the strength and bending capacity of Hybrid Timber can decrease by up to 43.5%.
