Shower tiles feeling soft or spongy, or even falling off of the wall can mean big problems. Why are they falling from the wall? Most likely, water has found its way behind the wall and is causing the tile to come off of the wall.
You frequently see the damage starting at the bottom of the shower and moving upwards. In many cases, it is simply a maintenance issue that has caused the damage. Simply paying attention to the caulking and grout can save a lot of headaches. By the time you notice the damage it is too late. The wall may appear bloated or it may cave inward, and you may even be able to move the wet portion of the wall by simply pushing on it.
Typically you want to get back to dry solid material. That means removing tiles and green board, and even insulation if on an exterior wall. If you run into mold, I would suggest you have it investigated by a professional in the field.
Once you get to dry solid surfaces, you can replace the damaged green board and reinstall the tiles and grout. The last step is to caulk the shower, and as we’ve seen, it is probably the most important step.