I used 1.5" Foamular on the floor covered with Drimax (slightly less expensive version of Advantech)3/4" no framing floor is solid as a bowling alley and is warranted to be waterproof for 500 days.I will never know will I? I also used 1.5" Foamular on ceiling and in wall voids created by roof lift. Then covered the walls with 2 layers of 1/2" foamular which got everything fairly smooth
and even. next project tongue and groove ceiling and bead board walls.
Its hard to be wrong when you live in Wright City!
There is no mechanical problem that cannot be overcome by a skillfully applied combination of brute force and ignorance!