Once the floor has been prepared and the layout lines have been marked, you’re ready to start tiling. You may choose to install all the tiles in one day, cutting perimeter pieces and pieces that go around obstructions as you go. Or, you could install only the full-sized tiles on the first day and then cut and install all the cut pieces after the mortar has hardened. Mortar often hardens overnight, but, if the air is humid, it could take a couple of days.

Try to plan your installation so you do not “tile yourself into a corner”; that is, you should never have to lean over more than 3 feet of just-installed tiles in order to install more tiles. However, if you must step on a just-tiled surface, lay down a sheet of plywood first to prevent the tiles from moving out of position.

Mix a batch of thinset mortar and apply it to an area about 3 feet square. Take care not to obscure your layout lines with the mortar.

1) Set the first tiles. Position the first tile so it is carefully aligned with the intersecting layout lines; to help with accuracy, you can butt it against a straightedge. Set the next two tiles and then insert plastic spacers at the corners.

2) Set the tiles & check adhesion. Press the tiles into the thinset so they feel firmly stuck. Pick up a tile and look at its back; nearly all of it should be covered with mortar. If it is not, you may need to press harder, back-butter each tile with a thin layer of thinset, or tap tiles with a beater board.

3) Line up a row. Along a particularly visible line, press a straightedge (the factory edge of a sheet of plywood also works well) to make sure this line is perfectly straight. Check alignment every 15 minutes or so—before any of the tiles have had a chance to start setting in the mortar.

4) Maintain an even surface. To make sure the tiles are at the same level, with no low or high corners, set a piece of plywood on top and tap. If you see a tile that is low at one corner, try pressing on the opposite corner. If this does not work, pick up the tile and add or subtract mortar from the back of the tile or from its position on the floor.

5) Keep it clean. Removing squeezed-out mortar as you go may seem intrusive to your flow of work, but it will be more difficult to remove the mortar after it has hardened. Use a shim, paint stick, or plastic spacer to clean out joints. The mortar should be lower than the tile surface at all points or it may show through the grout.

6) Install the cut tiles. When measuring for the cut tiles, be sure to take into account the width of the grout lines. Cut tiles using a snap cutter, nibbling tool, or wet saw. You may need to back-butter at least some of the cut tiles before installing them. Most cut tiles do not have to be cut precisely because they will be covered with molding.