Modular Multifamily Housing in Korea and its Future Role
▲ Research Specialist Boo Yoon-sub, KICT Department of Building Research
Prologue
One of the eco-friendly construction methods, in modular construction, modules produced at a factory are used to complete a construction project on site. At the same time as on-site construction such as bed excavation and foundation construction are carried out, the module is made at an off-site factory dedicated to modular fabrication and brought to the site for assembly. Accordingly, the modular construction method has the substantial advantage of being able to reduce the construction period by almost half because external factors that can delay the construction schedule on-site, such as particulate matter and civil complaints, are minimized. Modular construction can be divided into two types: the floor-by-floor method, in which modules are stacked on site, and the infill method, which involves installation as if inserting into a structure equipped with column-beam-slab (Figure 1). Based on the materials constituting the modules, the modules can be classified into steel-framed modules and concrete-based modules.
Steel-framed modules have advantages such as high strength, high durability, and excellent machinability, because modular beams, columns, etc. are fabricated using high-quality steel. However, unlike concrete modules, the steel-framed module requires separate details to secure fire resistance. In addition, compared to concrete modules, the production cost is relatively high, and it is necessary to solve the problem of being somewhat vulnerable to vibration.
Concrete modules have the advantages of high strength, fire resistance, excellent anti-vibration, and economic feasibility, as floors, wall units, etc. are fabricated using precast concrete (PC). However, since they are heavier than steel-framed modules, there is a difficulty in lifting for high-rises, which must be overcome for high-rise modular construction with more than 20 stories (Table 1).
Trends in Modular Multifamily Housing in Korea
Modular multifamily housing in Korea mainly uses steel-framed modules. As a national R&D demonstration project, the Korea Institute of Civil Engineering and Building Technology (KICT) promoted the public housing project of a Modular Demonstration Complex in Gayang-dong in Seoul (2017) together with the Seoul Housingㅍ& Communities Corporation (SH). It also constructed the Modular Demonstration Complex in Dujeong-dong in Cheonan (2019) jointly with the Korea Land and Housing Corporation (LH). Both were supplied as the first multifamily public housing to comply with housing performance standards. After that, public sector bodies such as local governments provided modular housing with six stories or less above the ground as rental housing.
The KICT is conducting a mid to high-rise modular public housing demonstration project (hereinafter referred to as “Gyeonggi Happy Housing”) in Yeongdeok-dong, Yongin, Gyeonggi-do in collaboration with the Gyeonggi Housing & Urban Development Corporation (GH). Gyeonggi Happy Housing, which at 13 stories (106 households) is the highest-rising public housing project in Korea, plans to apply the achievements developed by the mid to high-rise modular research group, such as design engineering, off-site construction method, and on-site management. The three-hour fire resistance pointed out as a disadvantage of the steel-framed modular housing above was secured for the first time in Korea through an accreditation test by an accredited institution, and on-site construction is underway with the goal of completion at the end of 2022.
The SH is carrying forward a 12-story modular public housing project in Garibong-dong, Seoul (246 households), and a 10-story modular public housing project (512 households) in downtown Seoul. The LH provided public silver housing (152 households) in Ongjin-gun, Incheon by applying the modular construction method, and pushing ahead with the modular public housing project in Sejong City, etc. The government is considering early move-in by converting part of the public housing in the third new city to a modular construction method.
For concrete modules, KC Industry, a private company, jointly developed a PC box-type module with the KICT and built a modular building for promotion purposes at its headquarters in Yeoju and its branch in Jeju. It entered the housing market focusing on private housing with one to two stories. In addition, it is expected that the PC box-type modular housing will be able to be supplied as low-rise multifamily public housing of five stories or less, as it has secured structural safety and residential performance.
Role of Modular Multifamily Housing
For modular public housing, it is most important to resolve the problem of lack of public understanding in relation to off-site construction, and dispel misconceptions about poor residential performance compared to reinforced concrete (RC) construction. After the completion of the Gyeonggi Happy Housing promoted by the KICT as well as the modular multifamily public housing promoted by the public sector, through a thorough review of housing performance, it is necessary to inform the public that modular housing can also secure residential performance equivalent to that of RC multifamily public housing. In addition, it is necessary to pioneer a housing market that applies a modular construction method.
Since 2015, the housing crisis has been exacerbated due to a decrease in the number of authorizations and permissions for housing construction, a surge in the number of households caused by the concentration of population in metropolitan areas and division of households, and a shortage of high-quality housing stock. The current housing policy focuses on large-scale housing supply that can be expected after the passage of at least five years, such as large-scale housing site development, reconstruction, and redevelopment. As such, it is difficult to satisfy the current demand for housing, such as for single or two-person households in downtown areas. If local governments and local housing corporations provide a fast and timely supply of modular public housing to small publicly owned sites, it will be possible to flexibly respond to the issue by utilizing the modular construction method to fill the gaps that are not affected by the housing policy.
