If water gets behind the tiles and in the grout mildew can grow and it will cause the adhesive to deteriorate.
Tiles falling off wall tile adhesive.
Since the tile is flat and in the same plane the wall surface must also be a perfect match.
Many people strip the loose tiles sand them and reposition with new adhesive.
Tile falls off wall organic glue skins over.
Though more common in an older home rogue tiles can be found in new homes as well.
Use gorilla glue to replace each one.
Incorrect tile grout used.
Use a glue that is gap filling.
This means it is thick enough to easily bridge differences between the two mating surfaces.
This is not just a threat for your tiles but also for your health.
Was the adhesive left on the wall for too long before you placed the tiles.
Make sure that the tile adhesive that you use is water resistant.
How do you fix it.
Over time the mortar holding a wall tile may fail to do its job letting a tile become loose and fall.
Or take them all down putting wax paper between each tile so they don t get damaged.
The most common cause for falling tiles is water infiltrations.
You should leave the tile adhesive to set for at least 24 hours before grouting the tiles.
Grouting has been done too early.
Press the new tile down over the adhesives you have just applied.
The adhesive needs to be applied evenly and on every tile.
Apply grout around the tile on the gaps between the tiles.
This in conjunction with skinned over adhesive is the root cause of your tile failure.
As ceramic tile gets larger the wall or floor surface must be flatter and flatter.
The wall surface could have been irregular with humps and dips in it.
Clean off the old stuff from the back of the tile and from the wall.
Then prep the wall and use the adhesive made specifically for the tile you have.
Thinset is best adhesive.
Otherwise the repair may not hold and the tile may also sit a little higher than the ones next to it.
If no adhesive is applied then the tiles will fall off.
Often the adhesive will skin over if exposed to the air for too long before the tile is placed this means the adhesive looses its suction so the tile does not stick properly.
Be sure to spray the wall surface with water to activate the glue.
Make sure that they don t come into contact with any water during this period.
Give the adhesives 24 hours to set.