The fatal collapse of a concrete canopy attached to a century-old building in Bangkok’s Samphanthawong district yesterday was caused primarily by the long-term deterioration of construction materials and weak balcony joints, said a structural engineering expert.
After visiting the scene, Assoc. Prof. Amorn Pimanmas, president of the Structural Engineers Association of Thailand, said that the main cause of the collapse was the deterioration of both concrete and steel reinforcement over time.
Exposed for decades to rain and moisture, the materials had corroded, significantly weakening the structure, he said.
Investigators found that the balcony had only been welded at certain points, rather than continuously along the entire joint, leaving it structurally inadequate to bear weight over the long term.
Inspections of nearby buildings found that many had similar construction characteristics and were of a comparable age, raising concerns that similar incidents could happen again.
Amorn said an earthquake was not a major factor in the collapse, as low-rise buildings of this kind are generally not heavily affected by seismic activity.
Vibrations from passing trucks may have contributed, but were only a secondary factor, he said. The real problem was that the structure had outlived its service life.
“Concrete structures typically have a service life of about 50 years, but this building was already more than 100 years old,” he said.
Following the collapse, the Council of Engineers urged the Bangkok Metropolitan Administration to speed up inspections of old buildings in the capital’s historic quarters, especially those with protruding balconies.
Engineers also warned that owners of neglected buildings could face both civil and criminal liability if structural deterioration leads to injury or loss of life.
Assoc. Prof. Suttisak Soralump, a geotechnical engineering expert at Kasetsart University, said building ownership carries legal responsibilities in the same way as pet ownership.
“If you own a dog and let it bite someone, you are responsible. The same principle applies to buildings,” he said, warning owners cannot ignore maintenance until a structure becomes dangerous.
The incident has highlighted broader concerns over the condition of old commercial buildings and shop houses in Bangkok, many of which were built between 1957 and 1977.
Thai PBS found that, during that period, building regulations were far less stringent than they are today, while structural design methods and concrete production technology were also more limited.
As these buildings age, the deterioration of materials becomes a growing safety concern, especially where there has been little or no regular maintenance.
Many of Bangkok’s oldest and most heavily used commercial buildings are in the historic city and traditional business districts. These include Samphanthawong district, home to Yaowarat, Charoen Krung and Talat Noi.
They also include Phra Nakhon district, including Khao San Road, Sao Chingcha and areas around the Grand Palace, where numerous old and heritage buildings remain.
Other high-risk areas include Pom Prap Sattru Phai district, particularly the Bobae and Plubpla Chai areas, which are major wholesale trading zones wherein buildings are subjected to heavy daily use and often store large volumes of goods.
Similar concerns apply in Bang Rak, Yan Nawa and Pratunam, where many roadside shop houses date back to Bangkok’s early urban expansion and have been in use for decades.
According to Thai PBS, another collapse happened in 2025, when another 100-year-old awning crashed down in the Samran Rat area, trapping five people inside a house. No injuries or deaths were reported in that case.
