First Modular Public Housing Project Opens a New Chapter in MiC

With the pressing housing demand in Hong Kong, the construction industry has been committed to improving construction efficiency, and Modular integrated Construction (MiC) has gained popularity in recent years. Hong Kong has implemented several MiC pilot projects and laid a solid foundation in MiC adoption. Ir Thomas HO, Chairman of the Construction Industry Council (CIC), has visited the site of “Tung Chung Area 99 (TC99)” project to exchange ideas with the industry, hoping to further promote the development of modular integrated construction methods in Hong Kong.

TC99 project is led by the Hong Kong Housing Authority (HKHA) and is expected to be completed by 2025. The project consists of five buildings and provides 4,800 units, with one building adopting MiC, making it the first public housing project in Hong Kong constructed using prefabricated volumetric modules for domestic flats. Mr. Rayson WONG, Chief Structural Engineer (Development and Construction) of the Housing Department, introduced the TC99 project during the event. He stated, " The fifth block features an L-shaped design which adopts the MiC, consists of 12 storeys and encompasses all four standard flat types which require two to four prefabricated volumetric modules for assembly." Considering the construction progress of the project, one of the buildings is selected to test the production, installation, and effectiveness of the MiC.

Combining Experience and New Technology

This project improves upon previous MiC experience and techniques. Mr. Rayson WONG described the difficulties in installing prefabricated volumetric modules side-by-side with stringent tolerance control and it is easy to create gaps between the modules which may lead to water leakage. Therefore, the TC99 project chose stitching the MiC modules by in-situ concrete to eliminate the gaps between MiC modules and thus their vulnerability to water leakage and long-term maintenance burden.

Additionally, the team aims to combine the independent walls of two MiC modules to reduce the overall wall thickness. They collaborated with the Nano and Advanced Materials Institute to develop connection technologies to construct composite walls that have a similar thickness as conventional concrete walls, increasing usable space and providing flexibility in building design. Moreover, the installation and connection of components procedures could be separated to streamline the process and reduce the need for on-site steel reinforcement bar fixing, thereby reducing the workload of on-site construction.

Transportation Challenges Settled by Policy Adjustments

One of the main challenges in constructing the TC99 MiC building is the transportation of the large and heavy prefabricated volumetric modules to the construction site. Currently, the road freight transport restrictions in Hong Kong is 2.5 meters in width and 4.6 meters in height. Mr. Rayson WONG mentioned, "Under these restrictions, the modules need to be cut into multiple smaller parts before transportation, resulting in more connections and complicating the installation process." After discussions with industry stakeholders, the Transport Department and the CIC, MiC projects may apply for appropriate permits, to extend the limit to 3 meters in width to allow greater design flexibility. Where necessary, temporary diversion measures are also implemented to overcome the limitations of narrow roads in Hong Kong, facilitating smooth installation.

Work Together to Promote High Efficient Construction

The CIC has continued to promote the development of MiC, its Chairman Thomas HO commended the significant breakthroughs achieved by the project team. He also expressed interest in the construction efficiency, and encouraged the team to further accelerate with their experience of traditional MiC, from completing a standard floor in six working days to four days. Representative from the Housing Department stated that they aim for faster construction and have been maintaining close communications with contractors, emphasising that the target to complete one storey in six days must be achieved and they believe that there is room for acceleration. The team will continue to ensure the safety of workers and project quality while striving for improvements. Once there is solid data and experience, the team will share it with the industry.

With a target of constructing approximately 100,000 public housing units in the next five years, the government emphasizes the need for efficient construction. Mr. Stephen LEUNG, Deputy Director (Development & Construction) of the Housing Department, stated, "Optimisation is not only required for the module production factories but also for logistics, on-site technology, and the transformation of local workers. With enhancements throughout the entire industry chain, we can continuously boost construction efficiency."

Looking ahead, the Housing Department aims to further improve on-site construction processes with three key principles: Off-site Prefabrication, modularisation with cross-trade integration, and Plug-and-Play. The long-term goal is to achieve "Plug-and-Play" functionality, which, if successfully implemented, would simplify the construction process and potentially elevate the construction productivity for meeting Hong Kong's housing demand.