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Traditional Japanese architecture employs the wooden post and beam structure. This construction method is used in everything from small homes and tea ceremony houses to large temples and shrines. POST AND BEAM EVOLVE
MASATO NAKATANI, photos MEIKEN LAMWOOD
Japan’s wooden post and beam construction method has unique features in its structure and joints. This traditional method is designed to gently deflect strong external forces like wind and earthquakes, rather than countering them head-on. Softwood makes it possible. It has less strength than hardwood but more elasticity. The joints are specially constructed to creep while of- fering resistance. When exposed to even greater forces, mud walls between posts provide a buffer, reducing the destructive force as they collapse. Such principles are used in various parts of a Japanese building, including the foundation, the core of mud walls and the way tiles are laid on roofs. Thanks to their elas- ticity, posts and beams return to their original positions once external forces recede. Buildings constructed in this way rely on a framework of posts and beams. This limits the need for walls, which tend to be fewer than in European buildings. Floors are raised above ground level to improve ventilation in Japan’s hot and humid climate. It is unclear when this method started and where it came from. However, the remnants of joints like this have been found in ruins dating back 4,000 years, so the wooden post and beam method was likely invented even earlier. POST AND BEAM THEN AND NOW Forests now account for nearly 70 per cent of Japan’s total land area, among the higher rates in the world. However, the country lacked sufficient forest resources until about 60 years ago.
In the 8th century, forest resources were so scarce that felling trees was prohibited. Constructing safe buildings from a limited amount of wood has long been a priority. Today’s conventional construction method became mainstream from 1945 onwards. At the end of World War Two, most major Japanese cities were burnt to the ground and building materials were scarce. Sturdy houses had to be produced with a minimum amount of material. Advances in structural mechanics and the use of nails to fix metal plates onto joints made it easier to calculate the strength of buildings, eliminating the need to rely on the experience and exquisite skills of carpenters. The cur- rent conventional method is a theoretical and computable system, a modernised version of the traditional method. DEVELOPMENTS IN JAPANESE WOOD DEMAND While residential construction is the main driver of wood demand in Japan, non-residential buildings are likely to play a vital role as a market for glulam in future, says Yasuo Toyoda , Executive Officer and Senior General Manager of the Wood Products Division at ITOCHU Kenzai Cor- poration. “The Japanese people have a long-time affinity for wood- en buildings. In our daily lives, we have always been sur- rounded by trees. Even today, the demand for wooden houses is strong. When people want to build a house, 80 per cent want a wooden one.” As a result, most of Japan’s wood demand is for residen- tial use. The transaction volumes of glulam used for posts and beams have increased by more than 20 per cent over the last 5 years.
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