Major general contractor Obayashi Corp. will start construction of a high-rise building made solely of wood in March -- the first full-scale wooden high-rise building in Japan.
It will have 11 stories for a total height of 45 meters, and is scheduled to be completed in March 2022.
"Using forest resources as wood will promote reforestation. We want to contribute to realizing a sustainable society," a company official said.
According to the plan, the building will be built as a training facility in Naka Ward, Yokohama for the Minato Ward, Tokyo-based company. Structural parts including the pillars, beams, floors and walls that support the building will all be made of wood. The company plans to mainly use domestic timber.
Technological advances have made it possible to build wooden high-rise buildings. Pillars are equipped with flame-resistant gypsum board inside, and can support a building without burning to the core even in a fire.
Under the Building Standards Law, if the center of a pillar is still strong after two hours of exposure to flames, it can be used to build up to 14 floors of a wooden building. This type of pillar is called "two-hour fire resistant." If "three-hour fire resistance" is confirmed, there is no limit to the number of floors allowed.
The planned building uses two-hour fire resistant pillars from the second to seventh floors. On the first floor where the pillars are exposed, three-hour fire resistant pillars will be used to prevent the spread of a fire in the neighborhood.
There are plans to use a seismic isolation structure. In addition, the strength of the pillars and beams is to be enhanced by a newly developed original joint technique. It is designed to withstand an earthquake with a seismic intensity of about 7.
In addition to Obayashi Corp., Sumitomo Forestry Co. in Chiyoda Ward, Tokyo, is planning to build a 70-story, 350-meter-high wooden building in 2041. Tamagawa University in Machida, Tokyo, plans to build a 9-story, 31-meter-high wooden dormitory at the end of 2022.
The development of high-rise wooden buildings is aimed at contributing to the prevention of global warming through the use of wood. Carbon dioxide absorbed by trees through photosynthesis is released into the atmosphere when the trees die, rot, or burn. However, CO2 is not emitted when used as building materials.
It is also expected to promote the domestic forestry industry. The Obayashi building will use about 1,500 cubic meters of timber, the equivalent of 150 ordinary detached houses.
"Wood itself is an environmentally friendly material. We can contribute to the establishment of a recycling-oriented economy by promoting its use," a Obayashi official said.
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