Reinforcements used in RC structures lose their load-bearing capacity by suffering from various deteriorations due to external effects. Insufficient cover thickness is one of these reasons. The topic of this study consists of the concept of inadequate concrete cover. Concrete cover values with different thicknesses were chosen, and it was aimed to show how these values affect the performance of a building. Base shear forces, stiffness values and target displacement were obtained for each different concrete cover. A reduction in concrete cover resulted in an increase in the base shear force and stiffness values. Insufficient concrete cover layer will reduce the strength of the reinforcement over time. This will negatively affect the earthquake performance of the building. It should be kept in mind that the main function of a concrete cover is to prevent external effects which adversely affect the strength of the reinforcement. In this study, information was also provided about corrosion caused by the lack of concrete cover, and solutions to the corrosion were presented.