Remove the detached and hollow-sounding tiles in the first case, or entirely in the second case, and apply the leveling, fiber-reinforced waterproofing floor mortar HYDROSTOP FLOOR or D-1, reinforced with D-20 acrylic emulsion, or D-1 FLEX in 2-3 coats of equal thickness (crisscross), in order to stop the moisture.
At least 3 days later, bond the tiles using the tile adhesive SUPER ACRYLIC or the flexible, high-strength tile adhesive GOLD, depending on the type of the tiles.
