Enabling lean through using shared mental models for precast construction in Singapore

Despite efforts in recent years, construction remains the most inefficient industry in many countries. Lean principles have brought about massive productivity growth in the manufacturing industry but application to the construction industry is still relatively unknown or unexplored. From a lean point of view, poor construction productivity is due to construction wastes, that is, defects and rework, overproduction, waiting and idle time, non-utilised resources, transportation, inventory, motion and extra-processing. One of the key movements in the Singapore construction industry is the adoption of precast construction which involves transforming construction into a manufacturing process with more off-site prefabrication to improve site productivity. Yet contractors are still encountering high occurrence of construction wastes and the pool of foreign workers have not reduced significantly. This calls for more theoretical research to understand the value of enabling lean in precast construction.To eliminate or minimise construction wastes, lean construction was adopted to model the precast construction process influencing manpower requirements. This is done using the shared mental models theory to understand how the lean principles enable people to work together to complete the tasks and work together effectively as a team throughout the entire precast construction process from the design, production, logistics to installation stages. Shared mental models is essentially the convergence among team members’ mental representations regarding various aspects of their team and tasks. The greater the commonality of their mental models, the greater the likelihood of the team’s ability to perform effectively. Teams who share mental models can understand other members’ roles and knowledge and become more effective to deliver successful outcomes.Besides the theoretical concepts, this study also presents the practical aspects faced by contractors through the conduct of questionnaire surveys to understand how the implementation of lean principles and shared mental models will affect the occurrence of construction wastes and hence the changes in the total mandays used during the precast construction process. These were further anchored by in-depth interviews with industry practitioners in the Singapore construction industry to validate the survey results.Collectively, the empirical findings collated from the building professionals suggest that a lean-enabled precast construction project leads to reduction in the occurrence of construction wastes and reduction in the total man-days used, both on-site and off-site, and the extent of reduction varies according to the different extent of lean construction implementation. The added effect of developing shared mental models among the team members is shown to further reduce the occurrence of construction wastes and result in better productivity performance. Hence, this study suggests that contractors should be integrating lean construction considerations with shared mental models development into the precast construction process to influence the impact on construction productivity in terms of the total manpower required.This study also proposed a neural network model for developing leading indicators that classify precast construction projects in accordance with the manpower changes achieved with the reduction of the occurrence of construction wastes. A case study was conducted and the results validated that the model would allow contractors to predict the risk of low construction productivity at an early stage and enable them to proactively take actions to further optimise the total man-days to be utilised in the subsequent precast construction stages.This study has contributed to the extant literature, shedding light on enabling lean through using shared mental models for precast construction in Singapore. A different approach is taken by assessing how team members involved in a precast construction project work together to minimise wastage of materials, time and effort throughout the precast construction process. This is distinct from the present site productivity measurement which focuses on the workers on-site. The construction industry will also benefit with contractors giving more attention to further develop their team’s shared mental models and implementation of lean construction principles to reduce the total man-day utilisation in their projects. Overall, this study has drawn an important practical implication with true accounts and reflections of real-life practices and experiences to help contractors to identify which areas to focus on throughout the entire precast construction process from the design, production, logistics to installation stages to further improve the rate of construction productivity.