Does your tile installer do this? Then you need a new installer!
Spot bonding, also known as dabbing or dotting, compromises the proper recommendations for tile installation. The tile isn’t completely bonded to the substrate and it creates bare spots behind the tile, allowing for the potential of water getting trapped between tile and substrate, mold growth, tile breakage, and in the case of floor tile, hollow sounds upon impact.
Spot bonding certainly saves time and money but opens you up to a number of issues that will ultimately cost you more in the end when repairs are needed. This method is one of the most common reasons for tile installation failure. Bypass the risk by using an installer that follows TCNA and ANSI specifications!