Use: Prodex Under Concrete or Reflective Bubble White Poly.
In my situation, after the 4” floor was poured we trimmed 1-3” off around the edges all the way around. Insulation really didn’t move any when floor was poured, just that contractor didn’t lay all the strips even. Had some running up the wall 5” an some 7”. If they would’ve had it all 6” evenly placed everywhere it would’ve required 2” trimmed all the way around before power toweling the floor.
So my theory on the advice of running 6” up the wall is for allowance for slight movement in the prodex so your end result is to have the cut off prodex edge right at the top of the finished floor on the outside walls. If gravel were used instead of packed fill sand like I used, I’m sure there would be even more movement from pouring, so the 6” recommendation is universal advice for both gravel and sand.
Hope this helps should any other customers inquire on the reasoning of running the prodex up 6” on the walls.
Thanks again for a GR8T product.