Concrete compression strength is a standard input for obtaining the elastic modulus of concrete. Calculated values of elastic modulus for the same concrete strength may vary according to different codes throughout the world since the formulas of the elastic modulus are different. Elastic modulus is one of the important parameters for structural design. Storey-drifts are also among the important structural design criteria directly related to the elastic modulus. Different elastic moduli values may lead lateral storey-drift calculations to differ from the code requirements. More dependable elastic moduli definition results in more dependable storey-drift calculations. Fuzzy logic algorithm, which generates more dependable results in engineering problems, is applicable to solve this problem. This study investigates the effects of storey-drifts on structural design; upper and lower boundaries of elastic moduli are predicted using a fuzzy logic algorithm in order to determine the effects of the elastic moduli on the storey-drift limitations found in different design codes. The study considers various design codes that are obtained worldwide. Study results also show that using a range of values for the elastic moduli is a more dependable approach for structural design safety, and that dependable storey-drifts are crucially important for structural design.