RT-033 Topic Summary
RT 033


Construction overtime has been frequently used as an inducement to attract labor and to accelerate schedule performance. While there may be positive short-term benefits to working an overtime schedule, the long-term consequences are typically viewed as detrimental. Understanding the effects of overtime scheduling is quite difficult because the factors affecting productivity in the overtime situation are numerous. Given that an overtime schedule cannot be avoided, there is little, if any, information available to aid in deciding which type of schedule to follow. Reliable data in this area are nonexistent.

The research conducted for RT-33 identified two overall goals to accomplish which included:

  1. To critique literature describing the effects of an overtime schedule on construction labor productivity.
  2. To present the quantitative results of a study into the effects on labor productivity of scheduled overtime. More specifically, to document a procedure for data collection and processing and an analysis methodology that can be used to quantify the effects of scheduled overtime on labor efficiency. Also, to describe a model explaining how scheduled overtime affects labor productivity.

The literature critique summary arises from the need that little is known about the origin of the overtime data, type of project, surrounding circumstances, and amount of data. Yet widespread assumptions have been made that the data and conclusions are reliable. This goal aims to clarify the above aspects of each data set.

The quantitative results are based on 121 weeks of data from four active industrial construction projects. Major contract disputes were not involved in any project, and the labor environment was good. Both union and merit shop labor forces were included in the study.

Key Findings and Implementation Tools

1 : Overtime Impacts Efficiency

All sources, except one, report consistent conclusions that efficiency is impaired as the number of hours worked per week increases, such as, scheduled overtime causes a loss of efficiency. (SD-60, p. 48) 
Reference: (SD-60)

2 : Length of Workday Factors

The results from analyzing the length of the workday were mixed. In some cases, the data showed that loss of efficiency was unrelated to the length of the workday. In several other instances, there was a near linear relationship between the loss of efficiency and the length of the workday. (SD-60, p. 6)
Reference: (SD-60)

3 : Length of Workweek Factors

The results from analyzing the number of work days per week on efficiency were mixed. In two studies, there were differences of about 7 percent (absolute) in the 6- and 7-day workweeks. In two other studies, there were no differences or they showed the 6- and 7-day schedules to be slightly more efficient than the 5-day schedule. For one study, the results were erratic. (SD-60, p. 34)
Reference: (SD-60)

4 : Optimized Overtime versus Work Progress

Determening the point of no return was simply a mathematical exercise based on efficiency curved. The point of no return is no more accurate than the efficiency curves themselves. Several reports stated that overtime should not be continued beyond two-thirds of the point of no return. The literature suggested that the point of no return for construction was considerably longer than in engineering work by a factor of 3 to 4. (SD-60, p. 43)
Reference: (SD-60)

5 : Additional Inefficiencies combined with Overtime

As overtime efficiency decreases, the research found that there was an increase in disruptions. The most consistent increase occurred in the category of resource availability. It is concluded that this increased difficulty in providing resources is the root cause of losses of efficiency. (SD-98, p. 45)
Reference: (SD-98)

6 : Factor Model

The Factor Model is a credible representation of labor productivity. The basis for this conclusion is that the disruptions were found to be strongly correlated to performance. The simplicity of the Factor Model makes it easy to understand how an overtime schedule affects performance and how to plan and manage an overtime situation. Using the Factor Model, it is easy to understand how the effects of scheduled overtime can be very detrimental to labor productivity. (SD-98, p. 6)
Reference: (SD-98)

Key Performance Indicators

Improved performance/achieved success, Improved craft productivity

Research Publications

Effects of Scheduled Overtime on Labor Productivity: A Quantitative Analysis - SD-98

Publication Date: 08/1994 Type: Research Report Pages: 57 Status: Reference

Effects of Scheduled Overtime on Labor Productivity: A Literature Review and Analysis - SD-60

Publication Date: 11/1990 Type: Research Report Pages: 57 Status: Archived Reference