According to the technical laying standards, ceramic tiles with dimensions higher than 30 × 30 cm there is a need for double gluing, that is, spreading the mortar adhesive on the back of the tile and also on the base (plaster or floor). For pieces with dimensions smaller than 30x30 or 900 cm², a single layer of mortar can be used, which must be applied to the plastering.

This indication is also shown on the mortar packaging. A good settlement consists of the complete filling of the back.