Modular construction offers several advantages, such as safe working conditions, fast construction, and high-quality end products. The project scheduling of modular construction should consider the time involved in the factory production, transportation, and erection processes of the units given limited resources (e.g., the number of modular units, available transportation, and workers) and project restrictions (e.g., the sequences of manufacturing production and on-site installation). However, current modular construction project scheduling techniques and previous academic approaches cannot deal with the overall project processes and production/on-site installation sequences simultaneously. This is one reason few mass-production multiple projects exist in the manufacturing industry. Moreover, it can lead to inappropriate project management guidelines and fail to minimize the overall project duration. This paper suggests a model for modular construction projects scheduling using a genetic algorithm. The results show that implementing both overall project processes and project requirements is an efficient way to develop a modular construction project schedule. The proposed optimization tool will help project managers allocate resources efficiently and reduce the completion time of multiple projects.

Modular construction, which involves factory-based modular unit manufacturing followed by installation at a construction site, has been recognized as one of the sustainable construction methods. Its advantages are known to be implemented through (1) standardized design, (2) standardized production method, and (3) large-scale development (mass production system). These three conditions are basic requirements for modular construction market expansion, but it is difficult to define that these conditions are a prerequisite for judging whether modular construction applied or not. Nevertheless, public development companies in regions or countries where modular construction has just begun thought that modular construction should meet all three conditions that are suitable for applying public construction projects. This is because it is difficult to compare conventional construction projects with similar conditions to modular construction projects. This paper analyzes the cost and duration data of three small-scale public construction rental housing (PCRH) projects involving modular construction in Korea. These cases presented herein include a public college student dormitory, public low-rise rental housing, and public mid-rise rental housing in small-scale development projects. Those were applied not standardized design (common design and regulation), but were reflected in each project’s demands (different design and regulation). To compare it, this paper analyzed 91 public housing provision projects’ construction data from 2011 to 2017 from one of the public rental housing provision companies in Korea. Among them, 19 small-scale public rental housing data were extracted for comparing with modular construction project data. The results show that, even if not standardized, the design and production process, and modular construction durations, were more effective—but costs were similar or expensive. Based on the conclusion drawn from three cases, this paper presents important considerations for the application of modular construction in other small-scale public construction rental housing projects from the perspective of public development companies.

Modular construction projects involve concurrent manufacturing production and construction processes for constructing the main structure and the foundation, on-site installation, and finishing work. Using process-driven project scheduling, it is difficult to analyze how different issues affect the overall project schedule and determine alternative solutions based on what-if scenario analysis (WISA). This paper proposes the classification of modular building construction projects as manufacturing driven, on-site driven, or a combination to improve scheduling strategies based on a schedule-driven approach. The scheduling focus is shifted from the working precedence (manufacturing → transportation → installation) to project scales and constraint changes. A discrete-event simulation model is developed for modular construction projects, and WISA is performed in actual modular construction projects. It is noted that compared with the existing WISA method that obtains construction schedule probabilities for specific tasks sequentially and independently, scheduling-based project classification and reflection of expected events are more effective in examining and determining scheduling alternatives. The proposed scheduling strategies and simulation model can enable project managers to assess several alternative scheduling solutions based on project characteristics.

The modular construction method is efficient for line production processes in factories. However, many modular unit production factories are having difficulty that how to prevent bottleneck effect, rework, and work congestion through the appropriate level of work packages composition by each work stations to achieve the smooth production. To solve these problems and improve production flow, the authors of this paper propose an optimized construction process at the factory production stage using a Dependency Structure Matrix (DSM) that considers the process approach based on flow of construction information in work activities. To test its effectiveness, the proposed process was applied to a modular factory and was found to reduce the number of main activities from 65 to 43 in comparison with as-is processes. Using this method, a manufacturing manager can thus improve production flow by analyzing the characteristics of work activities that form the plan for the manufacturing sequence decision phase. Moreover, while modular activities are independent of main assembly, there exist strong internal dependencies among these activities such that the manager can check the quality of each module. Furthermore, the research here might help save time in the manufacturing phase in factories.