The best foam for under a bath tub.

Always a good question.
For those of you plumbers that are using expanding foam under tubs, what is the best?
American Standard Americast tubs sometimes need something underneath to prevent the creaking and the squeaking. Some people use mortar too. I don't know if A/S is into mortar though.
My personal preference is mortar, but if you don't have access for that, then sometimes using a foam can with tubing can be useful.

I have a 2 piece from MAAX and they recommend a bed of mortar with a 2mil sheet of poly over it...

I'm interested to hear what everyone has to say...

How many pounds of mortar?

BUMP. I have heard not to use window/door or latex based foams because they crumble. Big Gaps expands too much... so that leaves the "regular" gaps and cracks. What is the most and least number of cans used before to achieve success?

Regulars! : How many pounds of deck mud / mortar / sand mix / hot plaster do you pour into your plastic sheeting sandwich under a 60 inch tub? This is poll-worthy since using too much mud can make it difficult to level the deck.

You don't level the deck with mortar.
You put a few piles under the tub, and the tub squishes the piles down.

I tried to pull a tub that had been foamed in the other day. We couldn't budge it.



This tub is there forever. I pitty the poor person that has to remove the tub to work on the pump at the far end.