Home constructed in 2003. Started an update to guest bathroom which is about 5 feet by 6 feet of blah cream colored 8"x8" tile. Im not working right now and figured I would jazz it up a bit. I have done small tile jobs before I this should be a piece of cake for me. Except for bathrooms, home is 100% oak hardwood flooring. Bathrooms are tiled with the plain jane stuff I described above. Tile is very hard ceramic coated red clay material. When I finally busted one with a hammer I notice the material below the tile isnt plywood subfloor as I expected. Rather it is some other gray material laid down in sheets screwed onto the plywood subfloor beneath. Unfortunately, the tile is not coming off cleanly and is bringing chunks of this gray material with it. What is this material beneath my tile? I think it might be Fiberock Underlayment but I am not sure. It is gray and in the area where it is cut for the HVAC register, the cut is smooth. Will the Fiberock only be under the tile, or maybe it is throughout the home? Do I remove and replace this underlayment or try to smooth it out? Danggit I think I just answered my own question. It will be easier to remove and replace this underlayment, right?