I have a fiberglass shower stall where the bottom has either slumped or the stall was installed wrong to begin with (it has no support beneath the surface that I stand on). The drain sticks above the level line so I have about 3/16" of standing water. I cannot easily access the bottom from the sides by breaking through a wall. I cannot get beneath from the front as I would have to raise the pan beyond the drain and would have to reset/fix the drain because I would have to disconnect and possibly end up breaking it in the process. And once this is done I would not be able to access the drain from beneath to fix.

As a temporary fix I built a cedar platform to help distribute the weight evenly across the bottom but still have the standing water problem of mold and mildew.

Can I some how jack up the bottom and put support directly beneath the pan surface?
Can I fill in the 3/16" with epoxy while simultaneously filling in the bottom with that expanding foam for additional support to keep future slumping from occurring?

The enclosure sits above concrete as it is located in the basement building. I would have about 4-6" to fill with support.

Flying Blue Eagle

If I were you I would contact a good reliable plumber in your area. It sounds like you have no exp. in this area,so save time and money. It sounds like it was org. installed wrong,they got the drain pipe set to high.:

adpolymers

yes, the answer is yes. Epoxy will fill it very nicely. I do it all the time. It is called parging an area. I have done it with straight epoxy since it self levels and I have done it with epoxy mortar which is much more efficient. I sell both, the mortar comes in a kit and would be a better choice I think.

Good luck