A hybrid conceptual cost estimating model for large building projects

Conceptual cost estimating is a challenging task under time and information constraints. This paper presents a practical hybrid conceptual cost estimating model for large building projects, including multiple mixed-use buildings. In this model, two different methods, assembly-based estimating and historical data-based estimating, can be used either together or separately at the work package level whereas a mixed-use building is considered a unique combination of multiple spaces for different uses. Comparing the two estimates reduces the uncertainty associated with using the limited project information in the early phase. The practical use of automated conceptual estimation has been achieved through a comprehensive and realistic approach that accounts for the estimator's role in the automated process, user acceptance of and confidence in the final estimate, and the efficient use of incomplete historical data. A case study using eight large building projects found that the proposed hybrid model can improve the accuracy of and estimators' confidence in the conceptual estimates.

► A hybrid conceptual cost estimating model was developed for mixed-use buildings.
► Two methods are used — assembly-based and historical data-based estimating.
► Estimate accuracy has been improved by the combined-use of two estimating methods.
► Practical use and effectiveness of automated estimating system has been considered.
► Estimators' role and efficient use of incomplete historical data were considered.