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ABSTRACT: This article examines the impacts of overtime on construction labor productivity, and consequently costs, for mechanical and electrical contractors. Overtime in this research is defined as the hours worked beyond the typical 40-hours scheduled per week. The article begins by presenting the effects of overtime and providing a representative sampling of the available overtime literature. Data for the quantitative analysis was collected from 67 projects located across the US by means of a questionnaire. Various statistical analysis techniques were performed to develop quantitative relationship curves, including the stepwise method, P-value tests, analysis of variance, and multiple regression. The results showed a one percent to 60 percent loss of productivity depending on the amount of overtime used and the type of construction performed. Case studies are presented to confirm the validation of the final regression model and also as examples of how to correctly use the model.
KEY WORDS: Productivity, overtime, construction, mechanical, and electrical
Mechanical and electrical contractors generally allocate 33-50 percent of a project's total budget to labor costs [5]. Of the typical project cost components (material, equipment, and labor), labor is considered the project element containing the most risk. The other cost components (material and equipment) are predominately determined by market price and consequently beyond the influence of the project management. As a result, the management of labor and its productivity becomes paramount in determining the success of a project.
Commonly in construction, project durations must be compressed and work accelerated to complete the project on time or on a date sooner than originally scheduled. There are three traditional methods to accelerate a schedule: overtime, shift work, and overstaffing. Overtime achieves schedule acceleration by increasing the amount of hours worked by labor beyond the typical 40-hours worked per week. Past research indicates that labor productivity can be negatively impacted by overtime, causing problems such as fatigue, reduced safety, increased absenteeism, and low morale [6]. Additionally, the extra work performed under the implementation of overtime comes at an increased cost, commonly time and a half. Andrew G. Smith [12] indicates that the premium cost of overtime and reduced labor productivity combine so that each productive hour gained costs an average of 300 percent of the normal straight time hourly rate. This research...