From among the many technological solutions for floors in residential buildings and in small public buildings very often rib-and-block floor systems are selected. The main argument convincing project owners to choose such solutions are their clear advantages, mainly the uncomplicated construction technology, no need to use advanced tools and equipment and the low cost. The introduction of harmonized European guidelines in the form of the EN 15037 series of standards made it necessary to introduce changes in the designing and constructing of these commonly used floor systems, whereby their manufacturers had to update their offers. This paper discusses the requirements and the main changes introduced by the EN 15037 series of standards in comparison with the previous guidelines and general calculations of reinforced concrete structures according to Eurocodes. Analyses concerning bending and shear ultimate limit states and serviceability limit states are presented. Critical points in the design of rib-and-block floors are indicated and the results of exemplary calculations for a selected floor are presented. In addition, a comparative analysis concerning the difference in the consumption of reinforcing steel for a selected floor system designed according to respectively the current and previous guidelines is carried out and its results are discussed.