Installed correctly the substrate is optimal and the floor will last for many years. When sealing a slate tile shower floor you can simply pour some sealer directly on the slate tile shower floor and use a towel to thoroughly saturate the slate tile shower floor with sealer. Inexpensive Update For Old Slate Flooring Using Chalk Paint Slate Flooring Slate Tile Floor Painting Tile Use a vacuum cleaner to remove any bit of dust that might have been dispelled by the powered buffer pads. How to seal a slate floor . Next make sure the room is well ventilated and pour your sealant into a paint tray. Seal each piece of slate individually following the manufacturers instructions. Grouting between slate tiles on the top-most layer is generally completed after the thin-set mortar sets. You can apply sealant with a spray applicator brush roller or even a sponge. Allow the floor to dry completely. Start rolling the sealant on from one wall to the other horizontally across the room maki...