Old vs. New Seismic Standards: How Earthquake-Resistant Building Requirements Changed After June 1981

Old and New Seismic Standards: Key Differences

"Old seismic standard" and "new seismic standard" refer to differences in the Building Standard Law's seismic design requirements. On June 1, 1981, the earthquake resistance performance required for buildings increased significantly. Buildings that received Building Permits on or after that date are classified as "new seismic standard," while those before are "old seismic standard."

Japan is earthquake-prone, and understanding the difference in seismic standards is essential when choosing a safe rental home.

Old Seismic Standards: What They Cover

Under the old seismic standard (before May 31, 1981), the primary design requirement was that buildings "remain standing in earthquakes of intensity 5+ (strong)." However, major earthquakes of intensity 6 or higher—such as the 1978 Miyagi Earthquake off the coast—caused significant damage, prompting a major revision of the standards.

Characteristics of buildings built under old seismic standards:

• •Can withstand earthquakes of intensity 5+ (strong), but safety becomes questionable in stronger quakes
• •Wall quantity and placement standards were looser than today
• •The 1995 Great Hanshin-Awaji Earthquake caused widespread collapse damage to old seismic standard buildings

New Seismic Standards: What They Cover

The new seismic standard (from June 1, 1981 onward) added the requirement that buildings "do not collapse or crumble in earthquakes of intensity 6+ (strong) to 7." Specifically, two levels of performance are required:

1. Moderate earthquakes (intensity 5+ / strong) — Buildings sustain minimal damage
2. Major earthquakes (intensity 6+ strong to 7) — Buildings may be damaged but must protect occupants' lives (not collapse)

According to data from the 1995 Great Hanshin-Awaji Earthquake, the collapse rate of new seismic standard buildings was less than 1/10 that of old seismic standard buildings.

The 2000 Standard: Current Seismic Requirements

In June 2000, the Building Standard Law was further revised, applying stricter seismic standards to wooden buildings. Specifically:

• •Ground surveys now required for wooden houses
• •Foundation specifications clarified
• •Stricter metal connecting standards for column and beam joints

Experts typically evaluate buildings in three categories: "June 1981 standard (new seismic)," "June 2000 standard (current)," and "pre-1981 (old seismic)."

How to Check a Rental Property's Seismic Status

Estimating by Age

Check the "year and month built" in the property listing to determine when the building was constructed. Properties built after June 1981 (Showa 56) should follow the new seismic standard. However, since the Building Permit date and completion date may differ, a building from "1981" could still follow the old standard.

For maximum safety, it's best to focus on properties built in 1982 (Showa 57) or later.

Check for Seismic Evaluation and Reinforcement Work

Even buildings built under the old seismic standard can achieve new seismic standard performance if they've undergone seismic evaluation and necessary seismic reinforcement work (seismic retrofit). Ask the property management company or landlord whether seismic evaluation and reinforcement have been completed.

Check the Disclosure Statement

The property disclosure statement required at lease signing includes the building's structure and age. While there's no legal obligation to disclose old seismic standard status, it's advisable to ask the real estate agent directly.

What to Watch For If You Rent an Old Seismic Standard Building

If renting an old seismic standard property, take these precautions seriously:

1. Prevent furniture toppling — Secure bookcases, dressers, and refrigerators to walls
2. Check hazard maps — Risk increases for old seismic standard buildings in areas prone to strong shaking (liquefaction risk, etc.)
3. Prepare an emergency evacuation kit — Be ready to evacuate quickly if the building collapses
4. Identify evacuation routes — Learn the building's exit paths and nearby temporary shelters in advance

Benefits of Old Seismic Standard Properties

Despite the risks, old seismic standard properties have a significant advantage: lower rent. They can be ¥10,000–¥30,000 per month cheaper than equivalent new seismic standard properties in the same area. If the property has been seismically reinforced, is in an area with solid ground, or is a 1–2-story wooden structure, it may be worth considering for budget-conscious renters.

Summary

When choosing a rental property, be aware of the June 1981 seismic standard dividing line. In earthquake-prone areas, it's highly recommended to choose properties built to the new seismic standard (completed in 1982 or later). Even old seismic standard properties may be safer if seismic reinforcement has been completed, so always confirm this with the property management company.

When selecting rental properties in Japan, geotechnical risks are often overlooked. Liquefaction and ground subsidence can cause serious damage to buildings during earthquakes. This article explains how to research geotechnical maps, the characteristics of high-liquefaction-risk areas, and key points to verify when choosing a property.