Ground Penetrating RADAR has no issues with tile or granite surfaces them selfs. The only issues that can arise with these kinds of flooring or walls are if a super fine wire mesh mat (1/2 inch by 1/2 inch)is used inside the grout layer. This can insulate the top of the floor from the GPR or X-ray signals. However, if the slab is elevated then it can be scanned from the underside. This will show the technician the contents of the slab up to the wire mesh mat layer that is under the tiles. Wire mesh that is embedded in the slab such as what was used in the example image (6 inches by 6 inches) is not a problem for an experienced technician.