The rise in urbanisation and subsequent demand for infrastructure accelerates the use of concrete as a construction material. Conventional design practices need large member sizes to fulfil architectural and structural requirements. Hence, the size of structural members such as slab, beam, column, etc., significantly affects the quantity of concrete used. This calls for the need to optimise the use of concrete to reduce the self-weight of structure. The present study explores the possibility of biaxial voided slabs as a substitute for conventional reinforced concrete slabs. A typical biaxial voided slab eliminates concrete from the middle of the floor slab by introducing voids and it leads to a significant reduction in self-weight, about 30–50%. However, these voids reduce the sectional area of slab concrete, which leads to a reduction in flexural stiffness and shear resistance. The behaviour of the biaxial voided slab subjected to two-way flexure is discussed. Experiments are carried out to determine two-way flexural behaviour of the two-way slab with sphere shape voids by adopting 16-point loads. The obtained experimental results of strength and serviceability criteria are compared for slabs with and without voids. It is found that the flexural capacity of the two-way slab with biaxial voids is the same as a solid slab, with a minor reduction in its flexural stiffness. Furthermore, an analytical study is carried out based on the yield line analysis to predict the flexural capacity of the slab and compared with experimental results. It is evidenced that 16-point load is equivalent to 89% of uniformly distributed load and the flexural capacity of void slabs can be predicted by using yield line analysis as used in the conventional solid slab. © Springer Nature Singapore Pte Ltd 2021.