Replacing a shower pan in a 32x32 alcove. The prior acrylic base was bedded in mortar on top of concrete subfloor. The new pan I intend to buy has an OSB and foam underside, seemingly meant for a flat wood subfloor.
The old mortar is uneven, chunky, from prior install. I'll try to grind or chisel it down to be a little more level, but it's still won't be level enough.
So the question: which approach should I take?
A) self-leveling cement, allow to dry, then simply set base on it
B) same as above but add a waterproof barrier between OSB and cured, level floor
C) bed the OSB base into thick mortar without taking the extra step of leveling first
The instructions seem to say that the OSB can be set directly into mortar, but worried about that because my subfloor is concrete, so potential for moisture to come up from below.