The objective of this work was to study the influence of such factors as the overweight of the slab with concrete mix at the concreting stage and complete loss of adhesion of the corrugated sheeting to concrete on the strength of composite slabs at the operational stage. The object of the study was single-span orthotropic composite slabs made on permanent formwork in the form of corrugated sheeting of grades H75, H144, H153 and TRP200. The coefficients of utilization of composite slabs at the operational stage were determined, obtained by increasing the weight of concrete mix with the development of the ultimate deflection greater than the standard at the concreting stage of composite slabs. The factors influencing the decrease in maximum bending moments in composite slabs at the operational stage with complete loss of adhesion of the corrugated sheeting to concrete were analyzed. The obtained data indicate the need to increase the working reinforcement of the slabs when corrugated sheet deflections occur at the concreting stage for different grades of corrugated sheet at different load levels and slab spans. Based on the results of the study, a conclusion was made about the need to carry out clarifying strength calculations when corrugated sheet deflections occur at the concreting stage, as well as under the influence of such loads and impacts that increase the risks of loss of adhesion during the operation stage.