[Richard]

I used some high zoom maximum sound deadening and insulating red colored stuff from the Lowes/HD. It was a huge mistake. In that in the transition from fixed floor to the floating floor, I can feel the floor flex if I am in bare feet. I would not use a padded underpayment if I were to do it again. I would use something like roofing felt if I wanted to protect the under lying floor from moisture. Of course you have to glue the underlayment to the flor, and then the LVT to the floor.