Accuracy in design stage elemental cost planning: an analysis of New Zealand data

Abstract

One aspect of client expenditure management that requires attention is the accuracy in design stage elemental cost planning which is a major concern for construction clients and practitioners in New Zealand. Several researches indicated that pre-tender estimating accuracies are significantly affected by the level of risk information available to the estimators. Proper risk analysis could offer at least a partial solution by reducing the variances between design stage elemental cost plans and final tender sums (contract sums) of construction projects. This study investigates the accuracy in design stage elemental cost planning with a view to identifying risk factors influencing the accuracy. Project data were obtained through interviews and thematic analysis identified the risk factors. Analysis of documents obtained from the archives of study participants (consultant quantity surveyors) complemented the responses from the interviews. Findings revealed deviations of elemental cost plans from final tender sums in the region of -14% and +13%. These results confirmed a significant disparity between elemental cost plans and final tender sums. It is conjectured in this study that the identified risk factors were responsible for the deviations observed. With this information, Quantity Surveyors are able to accurately forecast final tender sums of building projects from the cost plans through proper risk identification and subsequent further analysis, thus increasing accuracy.