TOKYO -- Sumitomo Forestry aims to plant a 350-meter wooden building in the Japanese capital in 2041 as it relies less on home construction in a graying and shrinking Japan.

The 70-story skyscraper would grace the Marunouchi business district under plans announced Thursday. It would be reinforced with steel for earthquake resistance. No such project beyond seven stories has been planned in Japan until now.

The mixed-use facility is seen housing retail, office, hotel and residential facilities in its 455,000 sq. meters of floor space. Construction costs are estimated at 600 billion yen ($5.5 billion).

The 185,000 cu. meters of wood needed would be enough for 8,000 of the company's built-to-order homes.

Sumitomo Forestry will research wood-based materials that can withstand flames for three hours. The plans also include waterfalls and such fire-resistant plants as Camellia sasanqua on the exterior of the building.

The company intends to build a 14-story, 70-meter wooden building as a steppingstone.

With housing starts seen decreasing as the Japanese population ages, Sumitomo Forestry is exploring other applications for wood materials and strengthening its focus on midsize and large buildings. In November, it formed a capital alliance with construction engineering company Kumagai Gumi, which built the Taipei 101 skyscraper.