Many tile showers and baths will fail for various reasons.  Water will find its way through the grout and caulking and start to eat into the walls and eventually to the joists.  If you feel that your tiles are loose and hollow sounding when tapped then your tile installation may need repair.  Remember it is often the case that there is much more damage behind the tiles then you may think there is. 

Many tile showers are built with wall board that is not suitable for tile showers.  In these cases it is best to remove the entire damaged wall section of tiles and rebuild the wall.

Then next step is to check the joists for damage.  In many cases the joists in the wood has been eaten away and there is need to reinforce the rotted joists.

The next stem is to check the joists for damage.  In many cases there is water damage in the wooden joists.  The first thing to do if the joists are damage is apply some liquid nails or polyurethane adhesive to the existing damaged joist.