Allow the underlayment to dry for at least 24 hours. When you are satisfied with the condition of the surface, you can proceed to install new tiles with thin-set mortar.

Your very best bet is to remove the old tile and the thin-set (the adhesive under it).

New ceramic tiles can be installed directly over old ceramic tiles or vinyl tiles with thin-set adhesives sold by tile dealers.

In this video, I walk through the process of removing old vinyl tile and stubborn adhesive from a plywood subfloor—a crucial step before installing luxury vinyl plank (LVP) in my income property ...