QUESTIONHollow Sounding Tiles - Recently the work of laying floor tiles in my house was completed. But i have found that there are some voids beneath some tiles. There are different types of voids. Some are at the centre of the tile. Again some are at the edge of the tiles. how can these be harmful???
ANSWERANSWER - If you tap on a ceramic or stone tile with a hard dense material, like a steel ball, where the tile is not bonded it will sound hollow (lower pitch sound) than areas that sound solid (higher pitch sound). If the whole tile and all tiles in the installation sound the same then it may not be a problem, but rather the nature of the floor assembly. It is when the sound is different within one tile or different from other tiles in the floor that it can be an indication the tile is not bonded at the hollow sounding spots. Those hollow spots are either voids where there is no thin-set support or it is a spot where the thin-set has loss its bond (attachment) to the tile or its substrate.
If the hollow sounding spots are voids then if something heavy and pointed is dropped or rolled on those unsupported spots then they will be susceptible to cracking or crushing. Corners of floor tile are particular susceptible to breaking when not fully supported by the thin-set. The ANSIA A108 industry standards state that floor tile for residential use should have at least 80% thin-set (adhesive) contact, but all of the corners and edges of those tiles have to have 100% thin-set contact (support). For interior wet areas (showers), exterior applications, and interior commercial applications the thin-set coverage should be 95% with full contact at edges and corners. Voids in the back of tile will tend to collect moisture that then can lead to other problems such as efflorescence stains or freeze thaw damages. Good Luck.