Can I Install Ceramic Over Floor Glue?

You should never install ceramic tile directly over any type of floor glue or adhesive. The chemical compounds in various types of flooring adhesives will be activated by the new tile mastic. The chemicals in the floor glue will begin to break down the new mastic and tile grout. Over time the tile will fail. Three options are available to correct this problem; remove the glue, cover the glue with concrete or install a new underlayment.  more