Changes Forthcoming to MLIT’s Article 4 Exemptions for Housing
Currently in Japan architects are not required to submit structural calculations in their building permit applications for houses that are 2 storeys and under with a total floor area less than 500m2. This exemption is known as the “Article 4 Exemption” and it has been helpful in minimizing paperwork and allowing builders and architects to easily obtain building permits. However, without this structural calculations requirement the risk is that in some cases housing designs do not satisfy basic level of quality and whenever big earthquakes occur there have been reports that a number of houses have collapsed. Victims and lawyers of such disasters have lobbied for the Article 4 Exemption to be abolished and MLIT finally has decided to address the issue. Similarly, the structural calculations methodology was based on housing built many years ago. In recent years, with the addition of solar panels, insulation and other amenities, homes in Japan have become much heavier than in the immediate post-war era. The increased weight signals the need to strengthen shear wall requirements within building standards provisions.
In 2023 MLIT will publish a notification to dramatically revise the Article 4 Exemption. While the exemption may not be abolished entirely, the expectation is that structural calculations will become a more commonplace requirement in Japanese housing. The final changes to Article 4 Exemptions are expected in 2025. Concurrent with these changes, MLIT is also expected to change building standards provisions to require houses to be designed stronger than the current existing standards.
While MLIT has not made the final decision yet, but it appears that they may propose lateral strength requirements that are 1.5 times stronger than the existing code. This underscores the need to develop appropriate shear walls which will meet the new standard as we must stay one step ahead of our competitors. So, we need to focus on this area and put all our energy into it.