Japan does not use modern nails to repair centuries-old temples. Instead, master craftsmen rely on an ancient woodworking technique

Centuries-old temples in Japan are still repaired without using modern nails, screws or metal brackets. In Japan, master carpenters instead continue to follow an ancient woodworking technique that has been passed down generations for more than 1,000 years.The method which is called kigumi involves carving wooden joints precisely so that they fit together like puzzle pieces. Beams, pillars and other parts of the structure are also shaped to lock into one another without the need for metal fasteners. This traditional technique is still used to restore some of Japan’s oldest temples and shrines. These structures have survived earthquakes, typhoons and changing weather for centuries.The craftsmen who carry out the work are known as miyadaiku or temple carpenters.

Why Japan avoids nails

The continued use of wooden joints is not just about preserving the tradition. The method also has practical advantages. Japan experiences humid summers, heavy rainfall, typhoons and frequent earthquakes. Metal nails rust over time as moisture enters the wood, weakening the joints and damaging the timber eventually. With wooden joints, however, the timber expands in humid weather and shrinks when the weahther is dry. This does not put too much pressure on the structure.It also helps the buildings withstand earthquakes as unlike rigid metal connections, traditional wooden joints move slightly during the seismic activity. The flexibility absorbs and spread vibrations across the structure, reducing the risk of serious damage during earthquakes. This is one reason many historic wooden temples have remained standing after repeated earthquakes.

Kigumi, a method of joining wood without using nails or metal fittings

Carved by hand

Making these joints requires years of skill and precision. Instead of cutting identical wooden pieces, miyadaiku study each piece of timber carefully. They examine the wood grain, natural curves and strength before deciding where it should be used in the building.Different joints also serve different purposes. For example, Tsugite connect two pieces of timber to create longer beams or pillars. Meanwhile shiguchi joints lock beams and pillars together at different angles to form the framework of the building, Ministry of Foreign Affairs of Japan details.Every joint also has to fit perfectly because even a small gap can weaken the structure. Most of these joints remain hidden inside the building, even though they are critical to its strength.

1,400-year-old tradition

Japan has more than 150,000 temples and shrines, many of them built using traditional wooden construction methods. Some of the country’s oldest temple carpenters trace their origins to the construction of Shitenno-ji Temple, which was founded in 593 AD.Becoming a miyadaiku takes years of apprenticeship. Carpenters pass on their knowledge to younger craftsmen. They teach them woodworking skills as well as how to understand the natural qualities of different types of timber.

The Yusuhara Wooden Bridge Museum

The craft is also valued for its sustainable approach. As wooden structures can often be taken apart, repaired and put back together without damaging the timber, individual components can be replaced without rebuilding the entire thing. This helps extend the life of the buildings and also reduces the waste.