The analysis of productivity in building construction
Productivity has for many years been an issue for the construction industry in Singapore. The industry is deeply concerned that construction productivity is not only below that of the manufacturing sector, but is also below the national average. The industry has identified several factors that have impeded construction productivity, namely, a shortage of suitably trained, skilled supervisors and workers; a weakening local construction workforce; and a large, mostly unskilled and transient pool of foreign workers. The main objective of the research programme was to assist contractors improve their site productivity performance. A three-pronged approach was adopted, comprising a review of current construction productivity issues affecting the Singapore construction industry; a survey of top civil engineering and building contractors to understand their perceptions on productivity; and a study of measurement techniques of site productivity for on-going building projects. The first phase of the research programme comprised a comprehensive study of construction productivity issues in the Singapore context, followed by an extensive questionnaire survey. The objective of the survey was to identify the perceptions of senior management of large civil engineering and building contractors with regard to: factors that would improve construction productivity; and problems encountered at construction sites. This phase of the research resulted in several recommendations to be made to industry in order to improve construction productivity. These recommendations included the recruitment and training of a new generation of skilled local workers; continuous upgrading of management and technical skills of supervisory staff; the study of long-term viability of construction automation processes; promotion of buildable designs; and extensive use of prefabrication to replace labour intensive operations. The second phase of the research comprised a study of productivity measurement techniques for various on-going building projects in Singapore. Two areas were investigated, namely: measurement of overall site productivity of projects on a monthly basis; and measurement of labour productivity of formwork, reinforcement and concreting operations. A prescribed productivity equation was used for measuring overall productivity, and data included monthly site manpower and monthly progress payments certified by the project consultants. Three categorises of building projects were investigated, namely commercial buildings, public residential buildings and private residential buildings. The findings of the research revealed that public housing projects, being simpler to construct, had higher productivity levels as compared to the other two categories of buildings. Research showed that for individual projects, the monthly productivity figures depended on the value of work done for the month. The productivity figures for commercial and private residential projects, were directly proportional to the architectural manpower used. An increase in architectural manpower would mean more activity in the high cost value architectural works which would increase the productivity figures by pushing up the monthly progress payments. It was also observed that productivity figures were generally lower at the start of the projects, due to the learning curve effect and the fact that manpower needed was mainly for structural works, which had a lower cost value than the architectural works. In the productivity studies of formwork, reinforcement and concreting operations, the research aimed to measure the manpower needed for each of the above trades in order to complete individual typical floors of selected buildings. This would enable a comparison of productivity figures on a floor to floor basis for each of the above three structural trades. The second phase of the research confirmed that it is possible for contractors to monitor site productivity of current building projects, study the variations in monthly productivity values and compare productivity performance of various projects within the same building category as well as for different categories.