I am building the pad for my Hearthstone and it requires a 1.2 Rvalue. I want the pad as low as possible since it is in a small room and I want max chimney height. Subfloor is wood and reinforced but the stove is heavy and many of the hearth building materials are also heavy. The pad will be 6 feet wide by 4 feet deep and tiled. I like extra big hearths vs. premanufactured ones. Micore you say? Great idea... So I have contacted the stove shops, the manufacturers of hearth pads, the building supply outfits, and even the listed distributors for micore in my state. Unless I want to buy a pallet of it then there is no micore available in the state. Most folks, even stove shops, think I am crazy. "Micore? What's that?" I have read through several threads and finding the stuff seems to be tough everywhere but impossible here. As I go down the list of accepted materials I find gypsum or plaster board. I assume that sheetrock with its combustible paper does not qualify as gypsum board in this application. So is there a more common name for the gypsum board? The R value is only 0.45 but that is twice as high as durock at 0.20. So it is not out of line. 6 layers of durock will get heavy, tall, and just bulky to deal with but it might be my only choice. Does anyone have any ideas or even better would be a puget sound source for micore?