I've been remodelling house and replaced my steel bathtub with a fiberglass one(which i really wish I would have stuck with another metal one). Now after 2yrs of installing it's starting to creak/make noises when I step around in it. I'm not sure if it's soft spots or the floor under it settling or something but would like to fix it before it cracks. Should or could I either raise the floor joist there if it is settling, or do they have some low expansion foam or something I can spray from basement into underneath the tub to even out the weight of it.
I'm an electrican by trade and really not fond of plumbing and ignorant on most of it so need some advice please