The field of use of the invention is the building construction and the direct use is for the ceiling, roof and foundation slabs. The proposed waffle slab construction contains crossed ribs oriented in two or more directions with prefabricated longitudinal reinforcement cages along the ribs, containing longitudinal lower bars (2) fastened in stirrups (1) having open upper sides. The vertical bars of the open stirrups (1) are bonded to the outside over the caissons formwork (3).