To install a ceramic tile floor, spread thin-set mortar over the installed backer board, and press tiles firmly into the mortar in a predetermined pattern, using spacers to ensure even installation. After the mortar hardens, remove the spacers, and spread grout into the spaces between the tiles. Let the grout harden before applying grout sealer and reinstalling fixtures such as toilets or baseboards.
A tile floor needs a sturdy substrate that won't flex to avoid broken tiles or an uneven floor. Water-resistant backer board is the most common substrate option. The base needs to be level to ensure the tile is level.
Do a dry run with the tiles before using the thin-set mortar. Find the center of the floor, and work outward so the tile looks symmetrical. The dry run helps determine if some of the tiles should be cut around the edges so they all fit.
Spread the mortar on a small section of the floor using a notched trowel. Twist the tile slightly while placing it to spread out the mortar. Place the spaces when installing the tiles. Add more mortar, and continue working until the entire floor is covered with tile.
The thin-set usually needs at least 24 hours to cure before grouting. Spread the grout into the cracks using a grout float held at a 45-degree angle. Scrape excess grout off of the tiles throughout the process to have less to clean up at the end. Wipe the tiles clean with a damp cloth when finished grouting.