Q: To get a paving job done on time, we're planning to have our crews work six 10-hour days per week. However, I'm concerned about the cumulative effect of long hours on worker productivity. Is there any data on productivity and overtime specific to the construction industry?

A.: While there is some published data specific to the construction industry, results aren't conclusive. The following information on overtime effects comes from a productivity summary report furnished by consultant James J. Adrian.

A study performed for the Construction Industry Institute involved a number of construction projects and crafts that included pipefitters, electricians, formwork carpenters, ironworkers placing rebar, and laborers for concrete placement. This study showed that productivity losses from overtime aren't automatic and that it may be possible for crews to work 60-hour weeks for several weeks without serious negative consequences.

A concept termed "the point of no return" is sometimes used to describe productivity losses due to overtime. The point of no return is the duration of the overtime schedule beyond which the cumulative output is no more than would have been achieved in a 40-hour week. Manufacturing-industry research found points of no return to vary from four to 21 days, as shown in the table below.

Point of No Return
Overtime schedule, Days (hours per day) Point of No Return
Optimum Stopping Point
5 (9) 21 14
5 (10) 12 8
6 (8) 10 7
6 (9) 8 5
7 (8) 4 3

A Business Roundtable report suggested points of no return for 50- and 60-hour weekly schedules of seven and nine weeks respectively, significantly higher than the values in the table. And a 1979 study by the American Subcontractors Association, Associated General Contractors, and Associated Specialty Contractors showed greatly differing results. The study concluded that, in general, productivity is greater than normal for the first few weeks of overtime. It also showed that seven weeks into overtime, worker productivity was still equal to the productivity expected for a 40-hour week. The point of no return wasn't reached until the 16th week of overtime. The summary notes that this latter value seems inconsistent with results of other studies.

There is much uncertainty regarding effects of overtime on productivity. Many studies citing detrimental effects are based on limited data and projects. And it's possible that some productivity losses result, not from fatigue or similar causes, but from the contractor's inability to provide materials or information at an accelerated pace.