: I am installing a 48 x 32 acrylic shower base (Jacuzzi) on a subfloor of 3/4" plywood and 1/2" cementboard. The subfloor is level. The instructions for the base say to use morter, but I think that is meant for installing over plywood alone, and I am concerned that if I use morter, the base may be raised up off the subfloor and won't be on the same plane as the rest of the floor. I have heard that a bucket of joint compound can be used to set a shower base, just to insure it won't ever shift or give. It seems to me the base should set directly on the cement board. Is this right? Can I use joint compaund?

Joint compond will turn back to mud when water is applied. I prefer materials that stay hard when wet. Terry