Wet processes are an integral part of the construction on the majority of today’s buildings, whether they are part of load-bearing or non-load-bearing structures. Moisture can be the cause of failures. Deformities in the form of failures are the most likely to be manifested as corrugation of wooden floors, formation of bubbles on linoleum, colour stains on floor surfaces, or non-adhesion of surface treatment to the substrates as well as adhesion of surface treatment to substrates, etc. It is necessary to deal with the possibility of the occurrence of these failures, for example, when the floor constructions are made of cement screed and other floor layers. The article is focused on the moisture measurements in the cement screed by several devices directly on the building site—the IN-SITU method. These measurements determine the shortest required time to dry the floor layer at a certain thickness. This time is eventually representing.