The purpose of this system is the use of lighter slabs in mid-floor construction. In the case of a conceptual design of a hotel, which nowadays is probably going to be built in a classical mid floor reinforced construction, the usage of the COBIAX lightweight construction without beams will highlight the advantages of this system. The system uses circular or oval hollow spheres, which are placed in the slab. This results in the creation of a lightweight slab, due to the reduction of mass, also a considerable reduction of columns, avoiding beams, reduction of the foundation plate thickness, decrease in floor height, etc. In this case, the architects will have the opportunity to design large and spatial structures, where the distance between the columns can reach up to 20 m. Reducing the amount of concrete of lightweight slabs in the COBIAX system, affects directly the reduction of CO2(carbon dioxide) emission. Based on studies made by a German research organization, each m 3 of concrete replaced with COBIAX, reduces approximately 210 kg of CO2 emission, which makes COBIAX method an ideal system for eco designers.* 1. The hollow spheres are placed in the neutral axis where the concrete has less shear or compression forces, reducing the volume of concrete.2. Reducing of the concrete mass that is under tension force up to 35 %, has a positive impact in the whole structure which enables saving building material. The Slab thickness varies from 240 mm to 600 mm. While most standard slabs, transmit stress forces in two or one direction, lightweight COBIAX slab system distributes the stress forces in several direction. The COBIAX slab needs up to 40% less load bearing columns, which offers architects better flexible opportunities in design.