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Abstract
It was found that a typical contractor wasted about 2.8% of the available time with waiting and other unproductive tasks (management related delays). Furthermore, an additional 2.7% of time was lost due to weather. On a deeper level of analysis it was established that the gangs wasted an additional 19% of their time. A tailored lean approach that was introduced on a construction site when a new phase started improved productivity by between 35% and 90%. The data after the improvements were significantly different from those before intervention at 95% confidence interval. There have been criticisms that lean thinking, although a neutral production philosophy, has had harmful effects on the employees working under such a system. To resolve all doubts about the methods introduced in this study having negative effects on employees, job satisfaction was monitored during their implementation. It was found that job satisfaction increased (in all facets measured) during the implementation of lean thinking on the construction site. Another question that was addressed during this study was whether tailored lean principles can significantly improve the performance of a typical contractor's administration procedures. It was found even during the part of the research concerned with on-site processes that the bonus system needed major changes. First, the software used needed to be changed. Excel spreadsheets were cumbersome and the analysis of the data collected was almost impossible. This caused enormous waste in terms of expensive data collection that was almost useless. Furthermore, it wasted huge amounts of hard disk space on the company's server, already a cause for concern to the company's system administrator. By using a database programmed in Access these drawback could be rectified and the next stage of the study could be tackled. The new integrated database saved much of the bonus surveyor's time. Time reductions were measured at 45% per bonus sheet while at the same time reducing error when processing the bonus. The time reduction further freed the bonus surveyor from weekly fire-fighting and thus made it possible for him to pre-target jobs and assist the men on site with their bonus sheets. The new bonus system additionally enabled the company to link bonus and estimating departments and for the first time made it possible to evaluate contracts constantly. This helped contracts and site managers to review their performance on site weekly and take immediate action where necessary. Although it could not be proved due to the time scope of the study, this integration of bonus and estimates should also produce more accurate and reliable cost and time estimates in the future. Finally, the use of Mean Value Theorem helped to minimise data collection and evaluation. By concentrating on the only 30% of the items which accounted for 90% of the costs, 70% of measurements and time-consuming data collection were eliminated. Naturally, this simplification brought some inaccuracy into the bonus calculations, however, the inaccuracy could be kept to a level below ±5% for Bricklayers, Joiners, Labourers and Scaffolders, ±10% Steelfixers and Plasterers. The practical consequences of these inaccuracies require further consideration.