I'm a bit confused. I'm working on gathering all the info and materials I need to build a hearth for our new/refurbished Fireview (coming in a couple weeks.) I've referred to the installation section of the Fireview owner's manual, which I will copy and paste here for reference... "If you decide to build your own hearth to go over a combustible floor, start with a plywood base. Over this apply: 1) a layer of 24 gauge galvanized sheetmetal,2) a 1/2 inch layer of an approved non-combustible insulation board (such as DUROCK cement board or WonderBoard Backer Board),3) decorative non-combustible material such as tile, slate, stone or brick." I don't know what R value the 24 ga sheetmetal has, but a 1/2" piece of Durock seems to have an R value of around 0.25. The decorative stuff as the final layer will add very little R value. So to add to the confusion, I feel like I keep reading on this forum that the Fireview needs an R value of 1.2 underneath. I've been scrambling with no luck to try and source Micore, without ordering it online for $100 for double the amount I really need. I will likely call Woodstock in the morning to confirm what the manual says. This will be a slightly raised hearth on top of a hardwood floor. I plan to put down a 4'x5' piece of 3/4" plywood, whatever cement/ceramic board that's need for require R value, then a top layer of broken up/mosaic of 1" marble/granite on top with mortar to hold it all together. Any thoughts? Thanks!