A known challenge of modular structural systems is to avoid the oversizing of its elements while allowing a wide variety of spatial layouts. Considering any given floor outline and the availability of square slab elements with three discrete bending and shear stiffness, this paper explores: 1) the minimal geometric and topological rules that ensure a positioning of columns satisfying serviceability requirements; and 2) for a given satisfying positioning of columns, the distribution of slab elements that minimizes the overall weight of the system. This study is part of a larger project aimed at developing a highly flexible floor system whose element dimensions do not constrain the positioning of the columns nor the shape of the floor plan. Hence, the structural system could be adapted over time to changing architectural needs.