The beds onto which flooring is to be installed can be defined as thin (4-8 cm) layer structures applied on top of pre-existing concrete substrates (floors), the surfaces of which are in general irregular and thus require a surface coating to provide the required flatness. Another important function of the bed is that of containing service tubing or wiring laid on the substrate and embedded in the structure (bed) onto which the flooring is to be laid. In general the bed acts as an intermediate layer between the substrate and the adhesive with which the flooring (ceramic tile, stone, wood, rubber, carpeting, etc.) is anchored to the bed. The requirements that a bed should comply with, in order to carry out adequately its function, are presented and discussed, and the role and the importance of both the manufacturer of the binder and the installer are emphasised, associated to the final objective of achieving a flat, dry, clean, stable and reliable cement screed.