ABSTRACTThe production of steel and concrete is responsible for the 15% of CO2 emissions worldwide, whereas demolition of buildings produces a significant amount of waste that goes to landfill. Steel‐concrete composite floors are currently constructed using a monolithic connection between the concrete slab and the shear studs. This practice makes the deconstruction of composite floors problematic. More sustainable solutions can be achieved by developing composite floor systems that offer the advantages of easy and rapid deconstruction and reuse of structural components. This paper presents a novel steel‐concrete composite floor system using precast hollow‐core slabs and a demountable yielding shear connection mechanism. Horizontal pushout tests were performed aiming at: a) studying the physical behaviour of the proposed shear connection; and b) evaluating the construction and deconstruction procedures by disassembling and reassembling one push out specimen. The experimental results showed that increased ductility and strength can be achieved by altering the geometrical characteristics of the yielding mechanism. All the component parts of the connection were undamaged and reusable apart from the yielding mechanism. Numerical models for push out tests were created using the Abaqus software. Comparison of the experimental with the numerical solution showed that the strength of the steel yielding mechanism can be reasonably predicted.