It is very common for improperly supported floors in fiberglass tubs and showers to crack. If you are having that type of a problem, then it is best to have it repaired before the bottom boards absorb too much water and begin to rot. If you are considering having a tub or shower floor repaired, one thing to be aware of is that no manufacture recommends foam as support because after some use, its supporting properties are deminished because of compaction.
