AN EXPLORATION OF THE CRITICAL METHODS FOR IMPROVING DESIGN STAGE COST ESTIMATES OF BUILDING PROJECTS: A THEORETICAL LITERATURE-BASED STUDY

Accuracy of early cost estimates is a major concern for clients and cost engineers. Several researchers have long expressed their concern about cost estimating inaccuracies by recognising that the accuracy achieved in cost estimating has been less than desirable. The essence of having accurate design stage cost estimate as a reliable budgetary tool is defeated if the factors that affect design stage cost estimating accuracy and the critical methods for improving the subject are not given adequate consideration in the estimation process. Hence, project objectives regarding cost, time and quality targets are threatened. This paper first identifies various factors affecting design stage cost estimating accuracy in construction practice. Also, it provides a review of the influencing methods for improving design stage cost estimating accuracy of building projects by demonstrating the theoretical context. The study is a literature-based theoretical exploration, and a preliminary part of an on-going doctoral research on the budgetary reliability of design stage elemental cost plan aimed at assessing the risk impacts on the variability between design stage elemental cost plan and tender sum. The outcome of the doctoral research will provide the platform at exploring causes of variability with a view to developing a predictive model which will help construction industry practitioners in New Zealand in coming up with a reliable and objective elemental cost plan that guarantees cost certainty. This particular study is a first step towards a comprehensive empirical research of securing design stage cost estimate as a reliable budgetary tool that guarantees cost certainty for building projects