Installing 12-by-24-inch ceramic tiles requires an installation method that guarantees adherence to your surface. The substance used for adhering your tiles must be easily spread, while still retaining a thickness sufficient to hold the larger and heavier ceramic tile in place. A thinset mortar, mixed properly and thoroughly, will act well as an adherent for your ceramic tile, but for the best results, your subsurface requires careful preparation beforehand. After which, you'll have to place the tiles into the mortar correctly. Once placed, the mortar will hold the tiles securely for years to come, with little maintenance required to keep the bond between tile and subsurface strong.
Clean the surface of the floor with pH-neutral cleanser. Use a mop or sponge to remove dirt deposits, but use a scrub brush if the dirt is more ingrained into the floor. Rinse the floor with clean water to remove any of the cleanser residue, and then wait for the floor to dry before continuing with the tile installation.
Use a chalk line to mark a guideline across the floor for tile placement. Measure the length and width of the tile area, placing a mark on the center mark of each line surrounding the tiling surface. Connect opposing center marks with the chalk line and then life the line from the surface of the floor slightly, releasing it to snap against the floor to create a mark across the surface. Where the lines meet is the center of the tiled surface.
Mix a batch of thinset mortar using an electric drill with a paddle bit attachment for thorough mixing in a large bucket. Add water to the dry mix, mixing constantly until you have a mortar with the consistency of peanut butter.
Spread the mortar onto the floor beginning at a corner angle created from the crossing guidelines and following the angle with enough mortar coverage to install about four tiles. Use the flat of the trowel to spread the mortar evenly across the floor, and then turn the trowel at a 45-degree angle to raise notches in the mortar with the notched trowel edge. The notches help to create an even coverage on the rear of the tiles once placed onto the floor.
Use the chalk lines as a guide to place the tiles onto the floor. Firmly press the tiles into place, using a slight twist upon final placement to spread the mortar along the tile rear. Place two tile spacers along the side of the tile before placing the next tile to create a uniform spacing between the tiles. Remove any excess mortar on the top of the tiles with a damp sponge during placement.
Check that the tiles are level by placing a carpenter's level across adjacent tiles. Make adjustments as needed to level the tiles, either by pressing high tiles further into the mortar bedding or by adding more mortar beneath low tiles.
Continue placing tiles onto the surface until you complete coverage of the row. When tiling toward a wall, leave a one-quarter-inch gap between the edge of the tiles and the walls to allow for floor movement. If a partial tile is needed, measure the partial tile space and use a tile cutter to score and snap the tile to size before placement. Continue covering the floor, working from the center outward. Wait two hours for the mortar to set before grouting.
Remove the spacers between the tiles and apply grout into the joints. Use a grout float to place the grout onto the tile surface and push the grout over the tiles into the joints between. Fill all the joints completely with the grout except for tiles bordering moisture-heavy areas such as bathtubs or showers. Fill those joints with silicone caulking instead.
Wipe the excess grout from the tile surfaces within 15 minutes of placement using a damp sponge. Wait an additional two hours and then go over the surface of the tiles a second time with a clean, lint-free cloth to remove any grout residue. Allow the grout 10 days drying time.
Brush a layer of tile and grout sealant over the grout lines in the tiles for stain protection. Wait 48 hours before using the tiled surface.