Comparative Analysis of Flat Slab and Waffle Slab Systems for Multi - Storey Buildings

This study presents a comprehensive comparative analysis of waffle slab and flat slab floor systems for multi-story building construction, evaluating structural performance, economic feasibility, and environmental sustainability. The investigation examines key performance indicators including structural efficiency, material consumption, construction costs, embodied carbon emissions, and constructability for both systems across varying span lengths (6m to 10m) and building heights. Waffle slabs, characterized by their ribbed cofferboard configuration with reduced dead weight, demonstrate superior structural efficiency for longer spans (>7.5m) through optimized material distribution. The system achieves material savings of 20-30% compared to flat slabs while maintaining equivalent load-carrying capacity. However, this advantage is offset by increased formwork complexity, extended construction duration, and specialized labor requirements, resulting in 15-25% higher overall construction costs. Flat slab systems offer significant advantages in construction speed, architectural flexibility, and reduced story height, enabling potential savings in building envelope and vertical transportation costs. The beamless configuration facilitates simplified formwork, faster construction cycles, and enhanced spatial adaptability for varied occupancy requirements. For shorter spans (<7m), flat slabs prove more economical despite higher material volumes. Life cycle assessment reveals that waffle slabs generate 5-12% lower embodied COâ‚‚ emissions due to reduced concrete consumption, though this environmental benefit diminishes when accounting for additional formwork materials and extended construction energy use. Serviceability analysis indicates that waffle slabs provide superior vibration control and deflection performance, critical considerations for residential and office applications. The study concludes that optimal system selection depends on project-specific parameters including span configuration, building height, functional requirements, and sustainability priorities. Waffle slabs are recommended for longer-span applications prioritizing material efficiency and vibration control, while flat slabs suit projects emphasizing construction speed, architectural flexibility, and moderate span requirements. A decision matrix framework is presented to guide structural designers in system selection based on weighted performance criteria.