Moving to Japan? Concerned about earthquake resistance?  Choose a property built after 1981

Main Points:

・Changes in Japanese law related to earthquake resistance

・What happens to buildings as they age

There are two key factors that you should consider when looking for earthquake safe homes in Japan: the building’s age and the method of the building’s construction. This article outlines why each of these aspects is very important when choosing a place to live.

The Age of the Building

Earthquake resistance varies by the age of the building. There are two reasons for this: changes construction laws and natural deterioration.

Changes to the Building Standards Law

In 1981, there was a revision of the Building Standards Law, known as the New Seismic Standards. According to the Cabinet Office’s “Information on Disaster Prevention” page, this new standard is a stricter version of the old standard. It was designed under the assumption that all future earthquakes would be stronger than past ones, and so more stringent building standards are required. Because of this, you can find earthquake-resistant buildings by looking for buildings built after 1981. 

The new standard was created with the intent of preventing building collapse and damage by large earthquakes (seismic intensity 6 to 7 on the Japanese Shindo Scale). It assumes that earthquakes with a seismic intensity of 5 or less will cause little to no damage. Proof of the superiority of these new standards can be seen in the aftermath of the Great Hanshin-Awaji Earthquake of 1995. Following this natural disaster, it was found that buildings which met the new earthquake-resistant standards after 1981 were less damaged.

Age-related Deterioration

While the age of the building is important because of changes in construction standards after 1981, it’s also important due to natural deterioration of structures over time.

Building Lifespan

The longer a building is standing, the more it deteriorates. The speed of aging depends on the type of material the building is made of. According to the latest study by Professor Komatsu of Waseda University, “Estimating the Average Life Span of Buildings,” (Japanese article) the average life span of a wooden house is 64 years. For reinforced concrete, a study by the Ministry of Land, Infrastructure, Transport and Tourism’s “Study Group on the Promotion and Use of Used Housing Distribution” put the average life span at 68 years. A building that is closer to the end of its life expectancy will be weaker against earthquakes. 

Repairs and Maintenance

In addition to age, it’s also important to confirm major repairs and maintenance the building has undergone to correct and prevent damage. A building that is not well maintained may be more vulnerable to earthquake damage regardless of age. For this reason, it is recommended that you ask about the building’s “track record of large-scale repairs” and “regular maintenance” before signing a contract. This will help you accurately judge the condition of the property. 

The Building’s Structure 

How a building is constructed (whether it is wood or concrete) plays a large role in its lifespan. Additionally, the structure of the building changes how it is impacted by earthquakes. There are three structural forms of buildings in Japan: earthquake-resistant, vibration-damping, and seismic isolation. The following is a summary of the characteristics of each. 

Types of Structures

Earthquake-resistant

In an earthquake-resistant structure, columns and beams within the building are designed to be strong enough to withstand earthquakes. However, there is still noticeable shaking and movement of furniture within the building. 

Vibration-damping

In a damping structure, a component called a “damper” absorbs the shaking of an earthquake. The amount of movement experienced in a damping structure is comparable to that of an earthquake-resistant building, but damage to pillars and beams is reduced.

Seismic Isolation

In a seismic isolation structure, laminated rubber is installed between the building’s base and the ground. This prevents the building from being directly affected by the shaking from an earthquake. As a result, the building moves less. This kind of structure is highly recommended as it shakes noticeably less than earthquake-resistant and vibration-damping structures, offering more safety and peace of mind to inhabitants. 

Conclusion

When looking for a rental apartment, it is essential to consider your personal safety during natural disasters. Properties built before 1981 are riskier due to changes in construction laws and natural decay. Furthermore, the way the building was made drastically affects how the building reacts to seismic activity. Please refer to these guidelines when looking for a property to find a home with the best safety measures.