Above the Floor Rough Bathtub Support

I am doing a shower to bathtub conversion in my basement. I have purchased an above the floor rough bathtub. My question is regarding the support underneath the tub. The installation specs say to use mortar, but the specs are also for the non afr tub. I don't think just mortar will give it enough support. Our plumber said use foam spray, yet he doesn't really want to do the job.... Anyway.... what about using stringers or wood supports under or a combo of both?

Mortar supports millions of tubs around the world...why wouldn't it work for yours? It doesn't need 100% coverage. Many people put down a bunch of piles, then push the tub into them, ensuring it is sitting level in all directions. If you install your ledger board(s) well, you can use them as a guide and push the tub down into the mortar until it touches the ledgers, then leave it alone until the mortar cures at least overnight.

The lip, or deck of most tubs is required to be supported by ledger boards. Most tubs are NOT designed to actually hang from the ledger boards, but only to prevent them from moving when, say, someone sits on the edge. They also prevent the tub from tipping.

SOme people put some plastic on both the floor and on top of the mortar so it's easier to remove the tub eventually and to prevent the floor from sucking out the moisture from the mortar. Mortar cures, it doesn't dry, and if it loses too much water by drying, it won't be as strong.

That is good information, thanks! I just wanted to make sure that the above the floor rough style tub would not be treated differently bc there is so much more area under than a standard tub.