New wall tile can be applied over ceramic wall tiles. However, wall tile should not be applied over vinyl tile unless a backer board is first placed over the existing tile.
Preparation work must be done before installing new tiles over old tiles to ensure a proper bond. Existing wall tile must be cleaned and roughened. The old tile should be sanded using 80-grit sandpaper. Once the tile has been roughened, it has to be cleaned. All particles and dust must be removed to ensure the new tiles adhere properly. New tiles can be applied to this surface using thinset mortar.