Besides plywood, any other materials needed underneath the bathtub before I install the fiberglass bathtub. The instructions call for a felt pad. I am thinking of applying the foam used for laminate/floating floors to deaden any sound from dropped items and to ensure no creaks when standing in the tub. What do you think?
That will work. The purpose of the felt (or the thin, foam pad) is to isolate any squeeks between the tub and the subfloor.
Some tubs are a little flimsy and can use more support - a mortar bed works best for this.
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