Tiles make durable and easy-to-clean stair treads. Use brightly coloured tiles for a striking, dramatic look, or earth tone or stone tiles for a subtler appearance. Select tiles that will cover your stair treads in one row and have a finished edge for the exposed side of the treads. Specially made stair tread tiles are available, or use bullnose tiles that have a finished edge or V-cap tiles that will cover the entire edge of the treads. Unless the staircase is enclosed by walls, use bullnose tiles on the exposed side.
Examine the treads on the stairs for cracks and worn areas. If you find cracks or other damage, measure and cut cement backerboard to fit on top of the treads and attach them to the treads with screws. If the wood stair treads are in good condition, skip this step.
Spread thin-set mortar on the back of a tile with your trowel. Place the tile on the tread at the top of the staircase. Place tile spacers between the tile and the adjacent stair riser and on the left and right of the tile. Lay the rest of the tiles on the tread until it is covered. Place a beater board on top of the tiles, and tap the board with a rubber mallet to push the tiles and mortar into the wood or cement backerboard.
Lay tiles on each stair tread, working your way down the staircase. Let the mortar dry overnight.
Remove the tile spacers from between the tiles. Spread grout over the tiles on the top tread with a grout float, pushing grout in between the tiles and between the tiles and the risers. Grout the tiles on the rest of the stair treads, working your way down the staircase.
Wipe the grout residue from the tile surfaces with a damp sponge before it dries and hardens. Start at the top stair tread when you have finished grouting the bottom tread and work your way down the stairs. It is safe to walk on the stairs carefully while the grout is still wet.
Run a tile spacer or the corner of a damp sponge along the grout lines on the top stair tread to create even grout lines. Repeat for the rest of the stair treads, working your way down the staircase. Let the grout dry overnight, following the manufacturer's instructions.