Uneven edges from tile to tile. When one tile sits higher than the one(s) adjacent to it. An acceptable amount of lippage should be up to the thickness of a dime or credit card. The possibility of lippage should be discussed between homeowner and installer before starting the project. Stone floors can be ground (see “Utilizing the toughest abrasives to sand away a measurable amount of stone. This step would be used to even out high tiles and is a separate process from our standard finishing services. Sometimes this step is also used to sand away a coating on the stone provided the installation is even. More”) but is not the recommended solution. Grinding can cause permanent changes that may be considered unacceptable.