Many of you seem to have raised up hearth pads, which means you just built or laid your hearth pad right on top of the existing floor. Fine in most cases, and even often looks nice. In my case, I would like to keep my pad as low as possible, even flush with my exising floor if possible. My requirement is an R value of 0.4, so that is easy, two sheets of Dura rock, or a sheet of Dura rock and some tile/stone on top are 0.4. My install is going on a 2nd floor, which has 3/4" plywood screwed to the joicing, and 3/4" oak flooring on top of that. The question is, can I simply cut out/remove the Oak flooring, and replace it with 3/4" Durarock next gen, and then lay my stone (1/2" Silver Slate) on top of it? That would meet the R value, and make it "almost" flush with my existing floor. OR, does this R value requirement need to be in addition to the exising flooring? Thanks in advance for the help. I'm going to buy everyone on here a beer when I'm done!