Outdoor tile must be strong and durable to survive the elements. Because of exposure to the elements, though, outdoor tile is subject to heavy staining that will mar its appearance and change its color. To prevent this, it is necessary to seal outdoor tiles so they don't absorb moisture. For non-porous tile, administering the stain after completing the installation process is fine, while porous tiles require a dual stain application during and after the installation. Once completed you can enjoy your tiles worry-free, as water washes right off without staining.
Brush a layer of the tile and grout sealer formulated for your porous tile type over the surface of the tile. Cover the surface with an even layer of sealant. Do not allow the sealant to pool or collect into tile depressions, and do not allow the sealant to drip over the sides of the tile. Grout will not adhere well to the sealed surface.
Remove excess sealant with the brush and spread it around surface. Allow the sealant to dry overnight. The sealant will protect porous tiles' coloring, which otherwise might be affected by the grouting application.
Place grout onto the tile surface with a grout float and push it into the joints between porous tiles. Press the grout firmly into the joints with the float, filling the joints completely. Within 15 minutes, wipe excess grout from the surface with a water-dampened sponge. Wait two hours and wipe the surface with a lint-free cloth to remove grout residue. Allow the grout to dry for 48 hours.
Sweep the tiles with a broom to remove any dirt or debris. Brush a thin layer of tile and grout sealer over the tiles and grout. Use a penetrating sealer that will soak into the pores of the tile and grout, sealing them and creating a protective waterproof barrier. Cover the tiles completely, creating a visible layer of sealer. Wait 24 hours for the sealer to cure.
Apply another layer of sealer for further protection after the waiting period, following the same process used with the first. Wait an additional 24 hours before using the tiled surface.