If a rental property such as an apartment collapses due to a disaster like an earthquake, the landlord may be held liable for the damages.
This does not apply in every case, and seismic performance plays a major role.
Here, we will introduce the characteristics of earthquake-resistant, seismic isolation, and vibration control structures for rental properties, as well as how to check them and the importance of earthquake preparedness.
Landlords of rental properties should use this article as a reference.
Check the Seismic Performance of Your Property!
Buildings are subject to seismic standards set by the Building Standards Act and its enforcement orders.
Construction is not permitted if these standards are not met.
Additionally, seismic standards have been revised several times over the years, and older buildings may not meet current seismic standards.
With that in mind, let's check the seismic performance of your current property.
How to Check on Your Own
There are ways to verify seismic standards yourself.
Check whether the following criteria apply to your property.
Year of Construction
First, check the year of construction.
If the building was constructed before May 31, 1981, it falls under the old seismic standards.
If it was built on or after June 1, 1981, it meets the new seismic standards and there are no major concerns.
Seismic standards are provisions under the Building Standards Act that specify whether a building's construction and design can withstand earthquake tremors.
The old seismic standards were enacted in 1950 and operated for approximately 30 years.
These standards required that buildings not collapse or crumble in a moderate earthquake (seismic intensity 5) expected to occur roughly once every ten years.
Therefore, buildings under the old seismic standards were not designed to withstand earthquakes of intensity 5 or greater.
This was related to the fact that seismic technology for large-scale earthquakes had not yet caught up at the time.
The new seismic standards, on the other hand, were enacted following the catastrophic damage caused by the 1978 Miyagi offshore earthquake.
At that time, seismic intensity 5 was recorded in Sendai, but building damage was extensive, with over 1,000 completely destroyed, over 6,000 half-destroyed, and over 125,000 partially damaged.
It was the scale of this damage that gave rise to the new seismic standards.
If your property still operates under the old seismic standards, you should arrange for inspection and repairs as soon as possible.
Building Structure
Next, let's look at the building structure.
For building structures, whether the statutory useful life has been exceeded is an important benchmark.
The statutory useful life refers to the number of years until a fixed asset's value is depleted.
The useful life by building type is as follows.
[Useful Life]
・Steel-frame construction (frame material thickness 3mm or less): 19 years
・Steel-frame construction (frame material thickness 3–4mm): 27 years
・Steel-frame construction (frame material thickness 4mm or more): 34 years
・Wood-frame construction: 22 years
・Reinforced concrete construction: 47 years
Regarding building structure, more robust structures are reflected in longer years, in order from wood-frame, steel-frame, to reinforced concrete.
However, this does not mean the building will collapse once this period has passed.
This is the useful life for depreciation purposes, so keep it in mind as a general guideline.
Condition of Construction
When checking seismic performance, it is also important to understand the condition of the building.
Of course, being within the statutory lifespan does not mean you can be complacent.
Even buildings with the same seismic standard can differ in seismic performance depending on shape and building materials.
The following are ways to visually check the condition of a building.
・Number of columns and walls
First, check the number of columns and walls.
Buildings with more columns and walls are considered to have higher seismic performance.
Check the number of columns and walls in your rental property.
・Shape: square or rectangular
Square and rectangular shapes are considered to have superior seismic performance compared to other shapes.
L-shaped, U-shaped, or irregular shapes place stress on joints during earthquake tremors, increasing the risk of damage.
・Structural check
When checking by number of walls, look into whether the structure is a load-bearing wall structure or a rigid frame (Rahmen) structure.
A load-bearing wall structure supports the building with structural walls.
It may help to picture stacked boxes.
It tends to be used more in low-rise buildings than high-rise buildings, and is considered to have high seismic performance.
The uniquely named Rahmen structure derives its name from the German word for "frame."
It is a structure that supports a rectangular building with vertical columns and horizontal beams.
It does not require walls and is used in reinforced concrete and steel-frame construction.
・Check for deterioration
As a method you can check yourself, look for any signs of deterioration.
Also check for visible abnormalities such as sagging floors, difficulty opening and closing doors, and cracks in exterior walls.
Request a Seismic Diagnosis Company
If you want an accurate assessment of your rental property's seismic performance, it is recommended to request a company that can conduct seismic diagnoses.
By commissioning a company, they can assess areas that a layperson would not be able to evaluate.
However, not just any seismic diagnosis company will do — there are several criteria to consider.
[Points to Note When Choosing a Seismic Diagnosis Company]
・The company should be registered with a local government or municipality
・The company should have a proven track record and extensive experience in seismic diagnosis
・The company should hold qualifications such as seismic diagnosis or seismic retrofit technician certifications
Try to choose a company that meets all three of these criteria.
In particular, if a company visits you, you may be tempted to sign up for a diagnosis on the spot due to convenience, but it is preferable to choose a company you are truly satisfied with and obtain an accurate diagnosis.
Earthquake Preparedness for Rental Properties…The Current Situation
While it is ideal for landlords managing rental properties to proactively pursue seismic retrofitting, the reality falls far short of this.
Why is seismic retrofitting lagging behind or not being done at all?
Seismic Retrofitting Is Falling Behind
Japan, a country where many disasters such as earthquakes frequently occur, experiences earthquakes of seismic intensity 6 or higher on a regular basis.
Approximately 20% of all earthquakes of intensity 6 or higher worldwide occur in Japan, making it impossible to know when a disaster might strike.
Furthermore, the Great East Japan Earthquake in March 2011 caused massive damage to buildings and human life, a memory that remains fresh.
There is also the possibility of a major earthquake occurring within the next few years, making it increasingly important to focus on seismic preparedness.
However, the reality is that seismic retrofitting in Japan is currently lagging behind.
Particularly for rental properties, costs have become a major obstacle, keeping seismic retrofitting from progressing.
Reasons for Not Retrofitting
One factor behind the lack of seismic retrofitting is that landlords are hesitant to proceed.
There are currently many aging rental properties, and retrofitting a building to meet seismic standards requires a significant amount of funding.
Seismic reinforcement alone is costly, and any amount that the landlord cannot cover will lead to rent increases.
Rent increases not only place a burden on current residents but also become a reason for them to move out.
Furthermore, residents may need to be asked to vacate during the retrofitting process, and there is no guarantee they will return after construction.
The lack of rental income during construction and the associated costs are also contributing factors to the delay.
The Risks of Not Retrofitting
While the importance of seismic retrofitting is understood, failing to retrofit places landlords at significant risk.
In fact, the 1995 Great Hanshin-Awaji Earthquake caused the collapse of many buildings, and many people were trapped beneath the rubble.
There were cases where apartments collapsed while surrounding buildings remained intact, leading bereaved families of victims to pursue liability claims against landlords.
In many cases, legal liability was ultimately attributed to the landlords, and it can be said that failing to retrofit carries a significant risk that could change one's life.
What Are Earthquake-Resistant, Seismic Isolation, and Vibration Control Structures? Check the Features of Each!
So far, we have explained how to check seismic performance and the current state of earthquake preparedness.
Here, we will focus on the characteristics of earthquake-resistant, seismic isolation, and vibration control structures.
About Earthquake-Resistant Structures
An earthquake-resistant structure is, as the name suggests, a structure designed to withstand earthquake tremors.
It is the most common structure and is adopted in buildings such as detached houses, condominiums, office buildings, and schools.
During an earthquake, force tends to concentrate on heavy parts of a building such as the roof and floors, and the building needs to support this movement and reinforce it in a balanced manner.
During an earthquake, a force called seismic force acts on the building, so diagonal bracing is added to walls and joints are reinforced with metal hardware to give the building structural strength.
About Seismic Isolation Structures
Seismic isolation is characterized by reducing the tremors felt in a building even during a major earthquake, compared to earthquake-resistant and vibration control structures.
To prevent earthquake tremors from being transmitted to the building, the structure separates the building from the ground.
While this may give the impression that the building is floating, special seismic isolation devices are installed between the building and its foundation to deflect the force exerted by the earthquake and reduce shaking.
These isolation devices consist of dampers that absorb tremor energy and rubber isolators that support the building.
The seismic isolation devices absorb earthquake tremors, making it harder for the building to collapse.
About Vibration Control Structures
A vibration control structure absorbs earthquake tremors within the building itself.
By installing vibration control devices consisting of dampers and weights inside the building, the mechanism reduces shaking caused by earthquakes.
In tall buildings such as high-rise office towers and tower condominiums, the upper floors tend to sway more, but adopting vibration control is said to reduce the sway amplitude even on upper floors.
While it may seem similar to seismic isolation, vibration control does not separate the building from the ground.
Although earthquake tremors are still transmitted to the building, the vibration control devices convert them into thermal energy and release it.
This allows even large tremors to be reduced, making collapse less likely.
Merits and Demerits of Earthquake-Resistant Rental Properties
What are the merits and demerits of rental properties with solid earthquake-resistant structures?
Merits of Earthquake-Resistant Structures
One merit of earthquake-resistant structures is the lower construction cost.
When constructing a building, seismic standards must be met under the Building Standards Act.
However, if incorporated into the design from the outset, no additional costs arise, and the building will naturally meet earthquake-resistant standards.
Furthermore, shorter construction periods are another major characteristic of earthquake-resistant structures.
Since it is the most widely adopted structure, no specialized work such as seismic isolation or vibration control is required.
The construction period itself does not need to be lengthy.
Additionally, fewer design constraints allow for relatively flexible design, which is another advantage of earthquake-resistant structures.
In the case of seismic isolation, challenges arise such as being unable to build a basement or needing to secure space for device installation, but earthquake-resistant structures do not face such major design-related constraints.
However, there may be some restrictions due to diagonal bracing and earthquake-resistant walls.
Confirming these in advance will prevent issues arising mid-project.
Demerits of Earthquake-Resistant Structures
Earthquake-resistant structures have both merits and demerits.
Unlike seismic isolation structures that separate the building from the ground, earthquake-resistant structures transmit earthquake tremors directly to the building, which is a demerit.
Depending on the height of the building, a strong earthquake could result in prolonged and intense shaking.
Particularly in high-rise condominiums, there is a tendency to continue feeling the sway even after the earthquake has subsided.
Furthermore, if large tremors are transmitted directly over a long period, secondary damage such as overturned furniture and falling objects is more likely to occur.
Even if the building itself is undamaged, there is a possibility that furniture could fall inside the unit causing injury, or that residents could become unable to move.
In such cases, it will be necessary to attach anti-tip fixtures to furniture and take every possible precaution.
Also, even if a building is sturdy, repeated experience of major earthquakes can cause partial damage, and if such damage occurs in multiple locations or worsens, there is a risk of collapse in the worst case.
After a major earthquake with strong tremors, or after experiencing repeated large tremors, be sure to carry out maintenance and inspections without fail.
Merits and Demerits of Seismic Isolation Rental Properties
Seismic isolation structures are one of the most resistant structures against major earthquakes, but they also have demerits.
Here, we will introduce the merits and demerits of rental properties with seismic isolation structures.
Merits of Seismic Isolation Structures
The merits of seismic isolation structures include reducing earthquake tremors, preventing building damage, and contributing to the prevention of secondary damage.
Reduces Earthquake Tremors
Compared to earthquake-resistant and vibration control properties, seismic isolation structures are the most effective at suppressing earthquake tremors.
This is the greatest merit of seismic isolation structures, and leveraging this strength, they are frequently adopted in high-rise buildings and high-rise condominiums.
Seismic isolation structures suppress tremors by separating the building from the ground.
Therefore, even if a major earthquake occurs, the tremors felt inside the building will be minimal.
Reduces Internal Building Damage
Next is the point that earthquake-induced damage to the building is less likely to occur.
When an earthquake strikes, invisible damage can occur inside the building.
Damage to internal components and joints can cause problems and reduce the overall safety of the building.
However, in a seismic isolation building, because tremors are reduced, invisible internal damage is also less likely to occur.
Contributes to Prevention of Secondary Damage
When an earthquake occurs, the stronger the tremors, the higher the likelihood that furniture and appliances will topple over or be damaged.
The majority of human casualties from earthquakes are attributable to such secondary damage from falling furniture and objects.
In a seismic isolation building, the reduced tremors mean that damage from falling furniture and objects can also be minimized.
Many people worry about large furniture toppling over or items breaking during an earthquake.
For such people, a seismic isolation rental property provides peace of mind.
Demerits of Seismic Isolation Structures
The demerits of seismic isolation structures include vulnerability to vertical tremors, higher costs, and a relatively short history.
Less Effective for Non-Horizontal Earthquakes
Seismic isolation structures use components called "isolators."
By layering rubber and metal plates, or rolling metal balls, the structure becomes resistant to horizontal tremors.
However, since the building itself must be fixed vertically to support its weight, isolators cannot reduce vertical tremors when they occur.
Vertical tremors are said to cause less damage than horizontal tremors, but this does not mean damage cannot occur, so it is considered difficult to completely eliminate damage.
Higher Costs
Compared to earthquake-resistant and vibration control structures, seismic isolation structures cost more to implement.
Additionally, seismic isolation buildings require regular maintenance, and the isolation devices must also be replaced.
Therefore, not only initial costs but also ongoing running costs are incurred, making the financial burden substantial.
Limited History and Fewer Contractors
The history of seismic isolation devices is still relatively short, and the number of contractors capable of handling seismic isolation structures is limited.
Generally, the rubber used in seismic isolation devices has a useful life of 60 to 80 years, but since this has not been fully verified, there are questions not only about the useful life but also about the technology itself.
With fewer contractors available, the options may become limited when searching for one that can accommodate your needs.
Merits and Demerits of Vibration Control Rental Properties
Next, we will introduce the merits and demerits of rental properties with vibration control structures.
Merits of Vibration Control Structures
The merits of vibration control structures include resistance to repeated tremors and typhoon winds, lower costs, and ease of maintenance.
Resistant to Repeated Tremors and Typhoon Winds
Compared to earthquake-resistant structures, vibration control structures can suppress tremors immediately after an earthquake occurs and are also resistant to repeated shaking.
After an earthquake, aftershocks frequently occur, and repeated tremors can expand the damage in many cases.
Vibration control is effective not only against repeated tremors from aftershocks, but also against shaking caused by strong winds and typhoons.
If you want to suppress not only earthquake tremors but also those caused by strong winds and typhoons, vibration control will perform effectively.
Lower Costs
Next is the lower construction cost.
Not only does it reduce earthquake damage more than earthquake-resistant structures, but it is also resistant to repeated tremors from aftershocks, and its lower cost makes it relatively accessible — which is also a major merit.
Since construction costs in particular tend to run high, being able to reduce them even slightly is attractive for property owners.
Easy Maintenance
Vibration control properties are relatively easy to maintain, and depending on the devices used, damper replacement and inspection may not be required in many cases.
Regular inspections are needed when rubber dampers or hydraulic dampers are used.
Rubber dampers are prone to deterioration due to temperature changes, and hydraulic dampers can develop oil leaks, so they require maintenance.
Demerits of Vibration Control Structures
The demerits of vibration control structures include the fact that they cannot suppress tremors themselves, susceptibility to ground conditions, and variation in effectiveness depending on installation location and quantity.
Does Not Suppress Tremors Themselves
Unlike seismic isolation structures, vibration control structures cannot suppress the earthquake tremors themselves.
Vibration control structures work by installing dampers in the building, which act as weights moving in the opposite direction of the tremors to reduce vibration.
Therefore, similar to earthquake-resistant structures, the impact of tremors is felt directly, and if the earthquake is severe, damage to the building is possible.
May Be Affected by Ground Conditions
Similar to earthquake-resistant structures, vibration control properties are also in contact with the ground, so if the ground is weak, the intended effect may not be fully achieved.
On soft ground, even if a vibration control rental property is built, the original vibration control effect may not be realized, and tremors may be felt directly.
Effectiveness Varies by Installation Location and Quantity
The effectiveness of vibration control structures is said to vary depending on the installation location and number of dampers installed.
Since there are specific locations where vibration control devices can be effective, they will not perform well if not installed in the appropriate positions.
Also, even if the position is correct, too few dampers will reduce their effectiveness.
When adopting a vibration control structure, it is important to identify a contractor experienced in damper installation.
Which Structure Should Be Adopted — Earthquake-Resistant, Seismic Isolation, or Vibration Control?
We have introduced the characteristics and merits and demerits of earthquake-resistant, seismic isolation, and vibration control structures, but which one should ultimately be incorporated into a rental property?
In reality, there is no clear "correct answer" standard for earthquake preparedness.
Whichever option you choose, merits and demerits exist, and the one you select is not necessarily the best choice.
If anything must be said, it comes down to what you are seeking from the rental property.
When considering the construction of a rental property, you would weigh factors such as the target demographic, surrounding environment, floor plan, and budget to select the most suitable option.
The same applies to earthquake-resistant, seismic isolation, and vibration control structures — various factors must be weighed and considered.
Most importantly, select a contractor who will carry out the construction correctly and without deficiency.
Rental properties in particular will be home to many residents for years to come, so they must be safe and secure.
In some cases, it is also possible to combine multiple structures, such as earthquake-resistant with vibration control, or earthquake-resistant with seismic isolation.
Of course, this increases costs, but making a property more resistant to earthquakes in order to achieve higher resident satisfaction is also one approach.
Earthquakes cannot be predicted as to when or where they will occur.
While making a property earthquake-resistant is extremely important, it is equally important to create an environment where each resident can be prepared for emergencies.
It is important to proactively communicate evacuation methods and evacuation destinations in the event of an earthquake on a regular basis.
Seismic Retrofitting vs. Rebuilding…Which Should You Choose?
If there are seismic performance issues with a rental property, some may be unsure whether to carry out seismic retrofitting or go ahead with a complete rebuild.
Here, we will introduce the merits and demerits of both seismic retrofitting and rebuilding.
Merits of Seismic Retrofitting
First, let's look at the merits of carrying out seismic retrofitting.
Potential to Increase Occupancy Rate
By carrying out seismic retrofitting, the building will meet seismic standards and be deemed safer, with a high likelihood of achieving a higher occupancy rate than before.
Improved seismic performance means that in the event of an earthquake-related disaster, the risk to human life can be reduced.
Subsidies and Tax Reductions May Be Available
When carrying out seismic retrofitting, it may be possible to utilize subsidy programs and tax reduction measures implemented by local governments.
While the specifics vary by prefecture, many municipalities offer subsidies for seismic diagnosis and seismic retrofit construction costs.
In many cases, reductions on fixed asset tax and city planning tax are also available, so it is a good idea to check in advance what measures your local government has in place.
May Increase Value If Considering Future Sale
If you are considering selling your rental property in the future, carrying out seismic retrofitting to meet the standards may result in a higher price than at present.
Of course, property prices tend to decrease with age, but whether the seismic standards are met can also serve as a key factor in the assessment.
Demerits of Seismic Retrofitting
Next, we will introduce the demerits of seismic retrofitting.
Costs Are Incurred
Seismic retrofitting varies in characteristics depending on whether earthquake-resistant, seismic isolation, or vibration control methods are used, but in any case, significant costs are involved.
One option is to raise rent to recover the high renovation costs, but even so, rental income will not increase suddenly, and the financial burden can become substantial.
Disaster Damage Cannot Be Guaranteed to Be Contained
Even after seismic retrofitting, it cannot be guaranteed that disaster damage will be completely prevented.
If the epicenter is nearby and the tremors are strong, the damage could still expand.
While the risk to human life may be reduced, do not be overconfident.
Residents May Need to Vacate During Renovation
In some cases, residents may need to vacate during the renovation period.
If residents must temporarily live in alternative accommodation, there may be considerable administrative work and coordination involved, so it is necessary to confirm this with the contractor in advance.
Merits of Rebuilding
Now let's look at the merits of rebuilding.
Easier to Increase Rent and Occupancy Rate
With a new building, it is possible to set rent higher than the original amount.
For older rental properties, rent reductions are unavoidable, but once rent is lowered, it becomes difficult to raise it again afterward.
A new building carries a lower risk of vacancies and is more likely to achieve a higher occupancy rate.
Repair Costs Are Minimized
Once the property is rebuilt and becomes new construction, painting and equipment repair costs will not arise for some time.
Even if repair costs are incurred due to malfunctions, being able to keep them to a minimum is a merit unique to new construction.
Advantageous at Time of Sale
Naturally, a newer and cleaner property will be more advantageous at the time of sale than an older one.
A property with a lower age not only carries higher land value but also receives a higher asset value assessment.
Demerits of Rebuilding
Next, we will introduce the demerits of rebuilding.
High Financial Burden
Rebuilding involves higher costs than seismic retrofitting.
Not only do you need to build a new structure, but demolition costs for the old property are also included, so it is necessary to weigh this against your budget carefully.
Vacating Costs Are Incurred
If there are current residents in the old property, they will need to be asked to vacate for the rebuild.
In such cases, vacating compensation may arise, and combined with the rebuilding costs, the financial burden is likely to increase significantly.
No Rental Income During Construction
Naturally, rental income will be zero during construction, so no revenue can be expected at all.
If you rely on rental income for your livelihood, rebuilding itself may not be possible without sufficient savings.
Earthquake-resistant, seismic isolation, and vibration control structures each have their own merits and demerits.
When carrying out seismic retrofitting on a rental property, it is important to fully understand the demerits as well as the merits before making a decision.
However, it must also be understood that whichever structure is chosen, there will be demerits and no clear criteria for which is best.
If you have seismic performance concerns and are considering renovation work, weigh your budget and values to select the most suitable option.
Frequently Asked Questions About Seismic Performance of Rental Properties
Q1. Are properties built under the old seismic standards dangerous?
Properties that received building approval before May 1981 under the old seismic standards do not have guaranteed safety against earthquakes of intensity 6 or higher. A seismic diagnosis and reinforcement as needed are recommended.
Q2. How much does seismic reinforcement work cost?
Costs vary depending on the scale of the building and the method used, but for a single apartment building, it typically ranges from approximately 1 to 5 million yen, while for condominiums, it can run into the tens of millions of yen.
Q3. If a rental property collapses in an earthquake, is the landlord liable?
If a landlord was aware of seismic performance issues and left them unaddressed, there is a possibility that the landlord could be held liable for damages.
