For studying of influence of cross-section bars on occurrence and development of cracks in reinforced concrete elements it is necessary to establish, how much presence cross-section bars changes size of the bending moment at which there is an occurrence of cracks. Article is devoted studying of influence of diameter of a cross-section bars on easing of cross section and distinction in formation of cracks in reinforced concrete elements reinforced with welded grids and grids in which longitudinal and cross-section bars are simply adhered to each other. The analysis tested before 12 ferro-concrete slabs is carried out and the plan of the future experiment is described.