Improving the accuracy of approximate estimates of building projects

This paper investigates the level of estimating accuracy in Singapore between 1992 and 1998. It compares the actual estimating accuracy against practitioners' expectations, and past studies. Forty-two sets of project data were obtained from six Singapore based quantity surveying firms. The estimating accuracy was found to be 1.09. This level of accuracy is below the expectation of 41 quantity surveyors (QS) who were surveyed. There is therefore a need to increase estimating accuracy further. Results also showed that there is no significant difference in estimating accuracy between this study and a previous study by Gunner and Skitmore (1999a). The implication of this finding is that longitudinally, there is no improvement in estimating accuracy over time. Moreover, for future studies on estimating accuracy, researchers can rely on cost data sets that are relatively dated, and from one source. Thirteen possible methods to improve estimating accuracy were tested in the fieldwork. It was found that the more important methods relate to having good quality and sufficient quantity of design information to prepare estimates.