When should a thin-set mortar be used as opposed to a ceramic tile adhesive?
Most ceramic tile adhesives have very high bond strengths in dry areas, which makes them excellent for drywall installations. Yet when adhesives are exposed to water, their shear strengths are dramatically reduced. Thin-set mortar bond strengths are less affected by water. As an example, the dry shear strength for OmniGrip is 760 psi and the wet shear is 145 psi. This is why ANSI recommends intermittent water exposure only and interior use for adhesives. Ceramic tile adhesives can take a considerable time to dry, usually a minimum of 24 hours before applying grout. When applying tile to dense surfaces such as existing ceramic tile, to impervious or vitreous tile such as porcelain, in high humidity, when temperature is below 60°F, or when setting tile over 6″ x 6″ drying time can be greatly extended beyond 24 hours. Thin-set mortars are preferred in these situations, although ceramic tile adhesives will perform. Manufacturers typically recommend adhesives more for wall installations; th
