I want to tile over our uneven stone fireplace. We Planned to level with thinset and backerboard screwed in on top of the thinset, however a carbide drill couldnt get through the stone to attach the backerboard. Based on some advice and googling we tried to just level the uneven stone with thinset, but it is still a bit uneven, particularly at two unusually high points in the stone, we also don't have perfectly sharp edges as the high points in the stone are higher than the surrounding floor with the lowest points originally being even. In an attempt to improve the situation we were told to smooth out the surface as much as possible, and tile with thinset over that, attempting to level the final surface with the tile by adjusting the amount of thinset under each tile. We sanded the thinset as much as we could but it didn't make a significant difference. The tiles we are planning to use are 3x6 marble. Would appreciate any advice on how to proceed before we attempt something else and potentially worse the situation via /r/DIY http://bit.ly/2GYuqQ4
