Time and Cost Efficiency Comparison of Conventional and Half-Slab Methods in High-Rise Building Construction

Abstract

This study compares the time and direct-cost implications of conventional cast-in-place slabs and precast half-slabs for the Building Monument using quantity take-off, labor productivity, the Precedence Diagram Method, and 4D Building Information Modeling in Revit and Navisworks. The third-floor conventional slab requires 194.96 m² of formwork, 13,710.44 kg of reinforcement, and 58.49 m³ of concrete. The half-slab layout contains 88 P1 panels, 44 P1-1 panels, and 44 P1-2 panels, giving 176 installed pieces. For a standard 2.4 m × 1.2 m × 0.08 m P1 panel, 2.88 m² is the plan area and 0.2304 m³ is the concrete volume per panel. The audited third-floor direct cost is Rp156.11 million for the conventional method and Rp206.88 million for the half-slab method under the conservative assumption that the quoted Rp805,000 vendor rate applies to every installed panel. The half-slab alternative therefore has a Rp50.77 million (32.52%) direct-cost premium. Nevertheless, BIM 4D scheduling reduces the project duration from 447 to 337 days, equivalent to 110 days or 24.61%, by replacing repeated formwork activities and their removal lag with panel erection and overtopping work. The results demonstrate a time-cost trade-off and show that panel quantification, vendor quotation scope, and critical-path validation must be verified before selecting the slab method.