A Discrepancy Analysis of BIM-Based Quantity Take-Off for Building Interior Components

Abstract

The more detailed building information modeling (BIM) is, the more accurate are the quantities that can be extracted in BIM-based quantity take-off. However, the time and cost typically allowed for modeling are insufficient to extract accurate quantities throughout a project’s life cycle. In addition, variations in quantity interfere with estimating accurate construction costs. Despite the recognition that extracted quantities can differ depending on the details of building interior components, the number and extent of discrepancies, or whether these would differ by material, is unknown. Therefore, this study identifies and analyzes the approximately 6–9% quantity discrepancy (QD) in quantities extracted from different building interior components, in order to improve the accuracy of cost estimation using BIM. The discrepancy was analyzed by comparing the extracted quantities via two different model types, specifically a compositely modeled object and an individually modeled object. These models were applied to four cases of interior work in residential units. Results indicate that the QD occurs non-sequentially and exceeds the loss rates for some interior materials. Furthermore, this study identifies the causative factors of the QD by common features observed in the particular materials and suggests modeling and measurement strategies for minimizing QD.