70-Story Wooden Skyscraper Planned for Central Tokyo

Sumitomo Forestry Co. Ltd. has announced that it plans to build a 70-story 350-meter mixed-use skyscraper in Marunouchi, a central Tokyo business district, by the year 2041. No commercial wooden building taller than 7-stories has been planned for Japan, until now.

The project, which has been dubbed W350 in reference to the its planned completion year falling on the 350th anniversary of the company’s founding, is estimated to cost 600 billion JPY (5.5 billion USD). This is almost twice that of conventional high-rise buildings using current technology, but the company hopes to reduce costs by making technological advances in wood-based construction.

Demographic Shift

As the population of Japan is aging and shrinking, companies in every sector of the economy have had to adapt in order to survive. Sumitomo Forestry and the forestry and construction industries, as a whole, are faced with a downward trend in housing starts.

The W350 skyscraper is a part of the company’s efforts to find alternative uses for wood materials, beyond single-family homes.

The mixed-use building will contain retail, office, hotel and residential facilities in its 455,000-sqm of floor space. It is estimated that it will take 185,000 cubic meters of wood to complete the entire structure. This amount is equivalent to what would be required to build 8,000 single-family custom-made homes.

Wood-Steel Hybrid Structure

Plans for the building call for a wood-steel hybrid structure with a ninety percent wood ratio. The building will be built around a brace tube structure, in which steel damping braces are placed throughout the column and beam frame.

The building will be built around a brace tube structure. Image: Sumitomo Forestry

The outside of the building, which was designed in collaboration with Nikken Sekkei, will be enveloped by a series of open-air balconies, as a central part of the concept is to let fresh air and sunlight into the building. Greenery will also be incorporated into the design: from the ground, through the balconies and up to the higher floors.

The outside of the building will be encircled by balconies and fire-resistant plants. Image: Sumitomo Forestry

The interior of the building will be made entirely of wood, with the aim of creating a relaxing space where people can enjoy the natural wood surroundings.

CGI rendering of the lobby of the planned wooden skyscraper. Image: Sumitomo Forestry

And in answer to the concern that may be at the top of most people’s minds, Sumitomo Forestry says it will research wood-based materials that can withstand flames for three hours.

Source: Sumitomo Forestry press release (Japanese)