Material defects and poor installation supervision may have contributed to the improper assembly of prefabricated flats at three light public housing projects in Hong Kong, experts have suggested amid a controversy over the new construction method.
Their analysis came after a series of incidents involving Modular Integrated Construction (MiC) flats across various public housing projects sparked concerns over the dependability of the new building technique that has been heavily promoted by the government.
The recent cases include water leakage at a subsidised housing home in Kwun Tong, alongside improper assembly identified by the government at three light public housing sites, all involving prefabricated flats.
An initial inspection by the Architectural Services Department at the three locations – in Siu Lam, Tuen Mun and Chai Wan – all managed by the Able and Chun Wo Joint Venture, found that screws had been either shortened or severed, and that structural connections showed signs of defects.
The screws are said to be vital for securing the MiC flats to the reinforcing concrete core walls.
“The assembly of MiC units demands high precision, requiring meticulous alignment of the prefabricated modules,” said Benny Chan Chak-bun, former president of the Hong Kong Institute of Architects.
He said that MiC required greater precision in connecting and assembling the units compared with traditional methods.
Chan said workers who discovered installation problems should have immediately reported them to the contractor rather than attempting to make fixes on their own.
“The contractor is responsible for site monitoring and needs to conduct a review of its site procedures,” he said.
Authorities said earlier this month that an independent team had been established to investigate the irregularities, and that several MiC flats might need to be dismantled to determine why workers assembled them improperly.
Director of Architectural Services Michael Li Kiu-yin had said that the MiC modules were all factory-made, with their “dimensions verified and certified before being sent out”, vowing to hold the contractor accountable if any wrongdoing was confirmed..
Chau Sze-kit, chairman of the Hong Kong Construction Industry Employees General Union, suggested the irregularities were likely to be a result of lax supervision rather than negligence by individual workers.
“It is unbelievable that workers would make this decision by themselves,” he said, noting that tasks such as enlarging holes on plates would only increase their workload.
Chau added that the standard procedure required workers to report issues to supervisors before proceeding with any modifications.
While stressing that a final report was needed to understand the underlying causes, he said the scale of the unauthorised operations implied that supervisory oversight was bypassed, indicating insufficient monitoring by the contractor.
According to the authorities, an initial inspection of 30 to 40 per cent of the modules revealed significant defects in a number of their structural connections, with about 6 per cent of the 4,000 screws examined found to be cut short or severed for the three light public housing projects.
About 20 per cent of the connecting holes on iron plates were also enlarged without authorisation.
An architect familiar with MiC projects, who preferred to remain anonymous, said he could not rule out that both material flaws in the prefabricated modules and weak installation supervision contributed to the problems.
He suggested that some of the prefabricated modules could have arrived with defects, prompting workers to carry out unauthorised on-site adjustments.
“The initial inspection of 30 to 40 per cent of the modules found significant defects in a number of structural connections .. indicating a high probability that the prefabricated modules might have issues themselves,” the architect said.
Earlier, veteran structural engineer Ngai Hok-yan also said that the issues could have originated from the MiC unit’s design and manufacturing process, making installation difficult.
He said that based on the photos he reviewed, there appeared to be initial design errors.
But Edward Chan Sai-cheong, former chairman of the structural division from the Hong Kong Institution of Engineers, said that prefabricated modules were generally produced with high accuracy and thoroughly inspected before leaving the factory.
However, he noted that the on-site assembly of MiC units posed greater challenges than traditional construction methods, as it involved hoisting and stabilising them with higher accuracy.
Asked whether workers were familiar with the MiC procedure, Chan said they usually became proficient with the process after completing the first and second floors.
He warned that the compensation and remedial work would prove complex and expensive, since defects such as shortened screws could be scattered throughout different sections of the buildings.
Chu Yiu-leung, the associate director of estates from the Estates Office at the University of Hong Kong, said that MiC modules were manufactured in controlled factory environments, which helped minimise errors.
He cited his experience with a hostel project on Pok Fu Lam Road that used the same method, noting that he encountered no difficulties, only that the installation process differed from conventional construction.
However, he acknowledged that recent incidents may have damaged public confidence in MiC, stemming from misunderstandings about the rationale behind the building method, and expressed the hope that more successful projects would help restore trust in the method.
In a reply to the Post, the Architectural Services Department said it aimed to complete its investigation report within a month.
“Subject to the outcome of the investigation, [the investigation team] will take the appropriate actions, including regulatory action against the contractors and related personnel as deemed necessary,” the department said.
The Housing Authority also said in a reply to the Post that the water leakage at the home in Kwun Tong was unrelated to the MiC construction method, stressing that the issue stemmed from shoddy workmanship during construction. -- SOUTH CHINA MORNING POST
