Introduction
When people start paying attention to seismic design, the first reaction is often: “Does that mean I can only choose new buildings built after 2023?” But the truth is—most existing condos in central Bangkok were designed, constructed, or even completed before 2023. While these projects may not fully comply with the latest regulations, that doesn’t mean they are all unsafe. The key isn’t the year, but the building’s design concept, construction quality, and any subsequent reinforcement measures. You don’t need to give up; you need to know what to look for and how to choose. This article is a practical checklist for anyone searching for a “pre-owned condo in the city center.”
1. Check the Developer’s Background: Is It a Large or Reputable Builder?
In an era before the new regulations were mandatory, developers who proactively invested in seismic design were already setting a high bar.
Large and medium-sized Thai developers like Supalai, SC Asset, and SENA, even for projects built before 2023, often incorporated “shear wall core designs,” “SD50 grade steel reinforcement,” or collaborated with renowned structural consultants (e.g., from Chulalongkorn University or AIT). This indicates they had the awareness and resources to invest in structural safety.
Conversely, smaller developers or resale projects aren’t necessarily dangerous, but you will need to invest more time researching, cross-referencing plans, or even asking directly for the original structural design documents or engineering reports.
The key isn’t just the brand name, but whether the developer had a habit of “keeping structural records”—this directly impacts your ability to verify its safety.
2. Assess the Floor Count and Structural Type
The more symmetrical and simple the structure, the more stable its seismic performance.
For older buildings, the number of floors and structural type are your first quick screening tools:
- Buildings under 15 floors, especially those with a “square, symmetrical design, many walls, and short column spans,” are generally better at dispersing seismic forces during an earthquake.
- Conversely, be particularly cautious of these features:
- Double-height lobbies (e.g., ground floor height > 4.5m)
- L-shaped, T-shaped, or Z-shaped structures
- Large areas of floor-to-ceiling glass with cantilevered balconies
- Open ground floors used for retail or parking (Soft-Story structure)
These design choices may have compromised structural continuity for “aesthetic appeal” or “functional space” at the time, creating risks of stress concentration and amplified inter-story drift during an earthquake.
If you’re not a structural engineer, start by observing the building’s exterior for obvious asymmetrical designs, then ask for floor plans or structural drawings for further verification.
3. Inquire About Retrofitting or Assessment Reports
What makes an old building scary isn’t its age, but “structural risks that have never been inspected.”
Buildings constructed before 2023 aren’t necessarily lacking seismic resistance; it’s just that there were no mandatory standards at the time. Their current safety needs to be verified through retrofitting, testing, or subsequent evaluations.
Here are some key points you can proactively ask about or verify:
- Has the building’s management ever commissioned a structural engineer to conduct a seismic assessment? → An assessment report typically outlines predicted damage under various earthquake intensities, structural weaknesses, and recommended retrofit solutions.
- Has any structural retrofitting or repair work been carried out? → For example, the installation of:
- Carbon Fiber Wrapping: Enhances the shear strength and ductility of columns and beams.
- Steel bracing or shear walls
- Dampers or base isolators: Reduce the energy transmitted from seismic waves into the building.
- Is a Structural Health Monitoring (SHM) system installed? → While not mandatory, an increasing number of high-end projects are proactively installing these systems to monitor building sway and structural health.
If the developer or management can provide this information, it not only shows they are proactive about preventive management but also gives you a solid basis for confidence when choosing a unit.
4. Pay Attention to Common Area Design
Seismic safety isn’t just about the main structure; much of the damage occurs in “non-structural elements”—especially in common areas.
In many earthquake incidents, the real cause of injury isn’t building collapse, but secondary damage like falling objects from height, shattered glass, or broken connection components. Therefore, when evaluating an older project, pay special attention to these areas:
- Sky bridges, rooftop pools, and cantilevered facilities → These are vulnerable to damage or even断裂 under horizontal shaking. Verify if they use reinforced connections, steel supports, or flexible expansion joints.
- Glass curtain walls and exterior cladding → If glass is improperly fixed, lacks seismic sealant, or wasn’t designed for wind pressure, it could shatter and fall during a strong quake, posing a risk to pedestrians.
- Evacuation facilities and escape routes → The building should have clearly marked escape stairwells, emergency lighting, fire doors, and posted earthquake evacuation guidelines (e.g., refuge floors, assembly points).
- Structural reinforcement at floor-to-floor connections → Especially at the junction of elevator shafts and floor slabs. Poor design here can lead to “inter-story shear failure” during an earthquake.
A safe older building should make you feel secure even in its hallways and common areas, not leave you guessing about hidden risks behind every decorative feature.
5. Avoid These 3 Types of “High-Potential-Risk” Buildings
Not all buildings are created equal. Even if a building looks modern and is in a great location, you should be extra cautious or avoid purchasing if it has the following structural characteristics:
| Risk Type | Characteristics | Potential Problem |
|---|---|---|
| Soft-Story Building | Often has a tall ground floor with few columns, common in older office buildings, shopping malls, or parking garages. | Most prone to “amplified inter-story drift” leading to collapse during an earthquake. |
| Irregular Structural Building | L-shaped, T-shaped, staggered balconies, or extensive cantilevered designs without reinforcement. | Uneven distribution of structural stress, unable to effectively dissipate energy during an earthquake. |
| Old Building with No Retrofit History | Designed before 1997 (Thailand’s first seismic code) and never retrofitted or repaired. | Structural standards are far behind current codes, unable to withstand moderate to large earthquake forces. |
These types of buildings are often the first to suffer severe damage in a seismic event. You don’t need to avoid them entirely, but you must only consider them with a professional assessment and a clear record of retrofitting.
Summary: Knowing How to Choose an Older Home is a Skill
Pre-2023 projects may be slightly lacking in terms of seismic codes, but this doesn’t automatically make them unsafe. The real key is: Can you understand its structure, construction methods, and history?
By avoiding high-risk types and choosing buildings with stable structures, responsible developers, and a record of retrofitting, you can achieve both quality living and seismic safety within a reasonable budget.
This home-buying process tests your insight and your understanding of risk. While others only look at location and finishes, you are learning to see if it can stand firm through the next tremor.
References: Department of Public Works and Town & Country Planning – Building Seismic Design and Structural Standards Amendment (มยผ.1301/1302-61) / Faculty of Engineering, Chulalongkorn University – Bangkok’s Soft Soil Basin and Increased Seismic Shaking / Engineering Institute of Thailand – Guidelines for Inspection and Strengthening of Old Buildings / DARI BIM Central Platform – Building Information Modeling and Structural Health Monitoring Standards / Thai PBS – Earthquake Preparedness in Bangkok’s Risk Areas
The sources cited in this article cover regulations, research, and news reports from 2021 to 2024, cross-referenced from original Thai materials. The content is for informational purposes only. For actual project evaluation, it is recommended to commission a professional structural engineer for an on-site review.
