In our opinion, no. We have sold lots of slate, and have never had any complaints that people were tripping on the cleft areas of properly installed slate. We have had some specifiers concerned about it, and have decided not to use slate, but those who went with it, were always happy, to our knowledge. One consideration is that there are usually some pieces within a slate shipment that the tile contractor should sort and not install. We always recommend that this instruction be indicated in the project’s stone specifications.
