Sumitomo Forestry, the lumber division of the Japanese finance and industrial conglomerate, has revealed its plans to construct in Tokyo the world's tallest wooden building, a 350m high skyscraper which would also become the country's highest building. Named W350, the wooden high-rise structure will have a total of 70 stories. Its braced tube structural frame would need 185,000 cubic metres of solid wood combined with steel columns, beams and diagonal braces. Thus W350 won't be a wooden building in the strict sense, as steel would still account for 10 percent of its structural makeup.

The internal braced tubular framework is also necessitated by japan’s high rates of seismic activity, as it would prevent deformation of the entire structure due to lateral forces exerted by earthquakes or wind. Completion of the proposed hybrid timber skyscraper in 2041 would mark the company's 350th anniversary.

Wooden, wrapped in live plants, and with enormous price tag

Once completed, the ambitious high-rise would be almost four times taller than the world's current tallest timber building, the 18-storey Brock Commons Student Residence in Vancouver. As reported by Dezeen, the skyscraper is designed by Sumitomo's own Tsukuba Research Laboratory who for this project teamed with Tokyo based Nikken Sekkei.

The mixed-use tower will host a hotel together with a menagerie of offices, shops, and some 8,000 apartments. From all sides, the rectangular block will be wrapped in rows of extended balconies adorned with live plants on every level, while the building's interior will be clad in pure solid wood. The planned timber frame landmark won't come cheap, as Sumitomo Forestry estimates its total cost at £4.2 billion, almost double that of a conventional high-rise building of comparable size and height.

Nevertheless, the company indicated they are looking to reduce the gargantuan figure by coming up with a new innovative technology, as it sees W350 a cornerstone of a new global initiative to encourage wider use of timber in cities. Sumitomo believes that wider use of wood in construction would create a more environmentally-friendly urban environment and increase sustainability and biodiversity, as the traditional material during its lifetime stores copious amount of carbon instead of releasing it back into the atmosphere.

High rise wooden structures gain popularity across globe

Even though historically timber buildings dominated Japanese cities, fire risk greatly reduced the use of wood in construction in the country after the Second World War. Yet with the 2010 Act for Promotion of Use of Wood in Public Buildings timber construction in Japan received a major boost, and latest examples of large timber public buildings in Japan include landmarks like the 2020 Tokyo Olympics stadium designed by Kengo Kuma. W350 is the latest in the recent series of timber High Rise buildings planned across the globe. These include a 300m tall addition to the Barbican housing estate in London proposed by PLP Architecture and a timber-framed high rise block designed for Toronto by Penda.

In his recent interview with iNews Andrew Lawrence, Arup structural engineer and timber specialist talked about growing worldwide interest in timber construction due to its sustainability credentials and its potential to speed up construction. Yet he suggested W350's final version would look very different to the current design and might rely on less wood than originally specified. Involved in a comparable project in Amsterdam, Mr Lawrence and his team found it quite challenging to build a 19-storey building comprised of approximately 80 percent wood and 20 percent concrete, as even that material breakdown appeared already pushing the boundaries for what can be achieved with structural wood in construction.
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