Japan to set new standards for longevity of wooden buildings

The Japanese government is set to introduce new standards on evaluating the durability of wooden buildings with the aim of significantly extending their legal longevity for easier financing and promoting decarbonization through the increased use of timber.

The Ministry of Land, Infrastructure, Transport and Tourism plans to evaluate the waterproofing of wooden buildings via third party agencies which, if the new criteria are met, could double the service life of such buildings to 50 years or more.

Longer lifespans are expected to make it easier for building owners to secure loans, with repayment terms typically set based on the longevity of properties.

Applications to undergo evaluations under the new standards, which will apply to nonresidential buildings such as offices, are set to open from April, the ministry said.

Rainwater is the leading cause of damage to beams in wooden buildings. The standards will evaluate a building's ability to withstand water penetration.

The service life of wooden commercial buildings, set for tax purposes, is currently 24 years, while that of reinforced concrete buildings is 50 years.

According to ministry data on buildings that began to be constructed in fiscal 2023, 88.4 percent of residential buildings with one or two stories, and 55.7 percent with three stories, were made of wood based on a floor space basis.

Nonresidential buildings accounted for 17.1 percent of one- and two-story wooden buildings and 3.9 percent of three-story buildings. For projects of four stories or more, wooden construction was below 1 percent for both residential and nonresidential buildings.

The wood utilization promotion act that came into effect in 2021 encourages the use of wood not only for public facilities but also for private buildings for businesses.

© KYODO