Japan’s Revised 2×4 Building Code Effective April 2025
The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has recently published the revised 2×4 building code, which will become effective in April 2025. The objective of this revision is to relax and tighten certain regulations.
Regarding the relaxations, rafter and joist spacings will be broadened, and there will be a reduction in the structural calculation standards for mid-rise wooden buildings. Despite predictions of a decrease in housing starts, these changes are expected to boost non-residential applications of 2×4 structures, thereby increasing wood usage in that sector.
On the other hand, the regulations will be strengthened by increasing the required amount of shear walls and complicating the methods of structural calculations for residential applications. This is necessitated by the contemporary requirements for housing to accommodate solar panels and thick insulation materials, which add significant weight compared to homes built under the current standards.
The MOCXION INAGI building, developed by Mitsui Home, is a five-story wooden rental apartment located in Inagi City, Tokyo. The structure features a combination of reinforced concrete for the first floor and wood-framed wall construction from the second to the fifth floors. This design includes a central core with high-strength bearing walls and a central corridor, allowing for multiple openings in the exterior walls, which enhances natural lighting and ventilation.Mitsui Home’s initiative with MOCXION INAGI is part of a broader effort to promote wood as a viable material for urban mid-rise buildings, combining environmental benefits with modern architectural design.
The revised 2×4 building code and projects like MOCXION INAGI illustrate Japan’s commitment to expanding the use of wood in midrise wooden construction, leveraging its environmental benefits and modern architectural design. However, the anticipated burden on architects and builders due to the new regulations may delay construction starts in FY2025-26.
To address these challenges, Canada Wood, in collaboration with the 2×4 Association, is developing structural calculation support tools. These technical developments will be crucial in adapting to the revised standards and preventing a decline in housing starts. Canada Wood will continue to advance these efforts in the coming years, ensuring that the benefits of the new regulations are fully realized.