QUESTIONIf moisture leaches up from the concrete floor of a ground floor condo could it cause the thinset to deteriorate? Resulting in hollow sounding tile and some of the tiles tenting up?
ANSWERANSWER - Thin-set mortars should not deteriorate from being exposed to moisture. Most thin-set mortars are used in showers and in pools and fountains.
Moisture that migrates into the concrete slab from the ground and into the tile can cause tiles to expand; particularly if the tile is very porous. If there are no movement joints filled with an ASTM C920 sealant at the perimeters or every 20 to 25 feet in interior areas not subjected to sunlight or every 8 to 12 feet if subjected to interior direct sunlight then those conditions can lead to the tile debonding, sounding hollow, and tenting.