Construction Labor Productivity Benchmarking: A Comparison Between On-Site Construction and Prefabrication

Construction labor productivity has been declining over the past sixty years, which has caused a decline in overall construction productivity. The traditional ways of managing construction projects and their delivery have evolved into an inherently inefficient and adversarial process. There was always a need to improve the way construction elements are constructed and delivered to the job site such as adopting lean construction.One way to achieve this goal is to prefabricate the construction elements off site and then deliver them to the site for installation. Prefabrication is a process of assembling building components in a remote location using a production line in a controlled environment and delivering the parts to the construction site for installation. Several researchers have compared prefabricating construction labor productivity to on-site labor productivity. These comparative studies were conducted at the industrial or project levels but not at the task level. Therefore, the results lack the comparative data analysis identifying the direct, indirect, and idle time that workers spend in both environments. The purpose of this research is to address this gap in the literature by conducting quantitative statistical analysis to determine the effect of prefabrication on construction labor productivity.A comparison of construction labor productivity (sq. ft/labor hour) between constructing prefabricated stud wall panels and constructing on-site stud wall panels was established. This research project was conducted using field experiments and the data collection procedure consists of observing construction workers assembling steel studs wall panels in a prefabrication shop as well as in a construction site using the work sampling data collection method. The data was collected from five construction projects located in Milwaukee and Madison, Wisconson. Data analysis was completed by comparing the prefabrication of wall panels to on-site wall panel installation in terms of construction labor productivity.The results of the research indicated that construction workers spend more direct time and less indirect and idle time in the prefabrication shop than on-site construction. Additionally, Labor productivity increases with stud wall panels size in both environments. Also, labor productivity in the prefabrication shop is higher than on-site construction for stud wall panels smaller than 90 sq. ft.This study provides a better understanding of the factors affecting labor productivity in both environments. The task level comparative analysis presented in this research aims to inform construction firms and contractors of the time allocated by workers in prefabrication and on-site construction, which can help them increase labor productivity and consequently improve construction productivity by identifying deficiencies in the construction process