Accuracy assessment of BIM 5D-based quantity take-off for concrete and reinforcement works: A case study of a three-story building project

Accurate quantity take-off is essential for construction cost estimation, procurement, and project control, particularly for reinforced-concrete structural works. This study evaluates the accuracy of BIM 5D-based quantity take-off generated by Tekla Structures and Cubicost for concrete and reinforcement works in a three-story building project in Surakarta, Indonesia. A quantitative comparative case-study design was applied using the same structural drawings, reinforcement details, manual calculation recapitulations, and consultant bill of quantities (BOQ). Manual calculation was treated as a controlled analytical reference rather than an error-free ground truth, while the consultant BOQ was used as a secondary practical benchmark. The analysis used absolute deviation, percentage deviation, mean absolute percentage error (MAPE), root mean square error (RMSE), mean bias, Bland-Altman limits of agreement, and R² as supporting exploratory indicators. Based on the corrected element-level quantities, Tekla Structures and Cubicost produced concrete deviations of 1.803 m³ (0.30%) and 3.341 m³ (0.55%), respectively. For reinforcement, Tekla Structures and Cubicost produced deviations of 9,879.109 kg (9.07%) and 1,379.923 kg (1.27%), respectively. Deviations relative to the consultant BOQ ranged from 11.83% to 12.36% in the project-documentation comparison. The findings indicate that concrete quantities were relatively stable because they were primarily geometry-based, whereas reinforcement quantities were more sensitive to modelling assumptions, detailing rules, and extraction settings. The contribution of this study is a case-specific BIM 5D validation framework that separates analytical accuracy from BOQ agreement and highlights the importance of work-item sensitivity in structural quantity estimation.