Prepare the Bare Floor

• 1). Locate any dips in the concrete floor by placing a flat wooden board on the floor's surface in a corner and looking for dips beneath the board. Move the board over the floor little by little, checking for dips and marking any low spots you find with chalk.
  
  
• 2). Fill in the low spots in the floor with leveling compound, using a trowel. Run the edge of the trowel you used to spread the compound over the surface of the floor to remove the excess compound, and then allow the compound to dry. If the compound settles below the surface of the floor, add more compound and allow the compound to dry again.
  
  
• 3). Sand the areas where you used compound to make the filled spots level with the rest of the surface. Next, clean the floor well, using a mop and grease-cutting soap, such as dish soap. Once the floor is clean, rinse the floor with buckets of water or a garden hose.
  
  
• 4). Spread concrete sealer over the entire surface of the floor, using a paint roller, once the floor has dried after its cleaning. In areas that you cannot reach with the paint roller, such as the edges and corners of the room, spread the sealer with a paintbrush. Allow the sealer to dry for six to eight hours, and apply a second coat to the floor.
  
  

Lay 12-Inch Tile

• 1). Find the center of the flooring area in the basement that you want to tile by measuring down each wall and marking the middle, and then snapping chalk lines between the opposite walls of the room. The lines should cross in the center.
  
  
• 2). Spread tile adhesive at the center of the room in one of the corners created by the crossing lines. Put down the first tile to line up with two of the lines. Next, place spacers against each side of the tile, and line the next tiles up with the first.
  
  
• 3). Continue out toward the walls, spreading adhesive and laying each tile directly against those before it, with spacers in between all the tiles.
  
  
• 4). Go over the tile floor with grout after the tile adhesive has dried for 24 hours. Covering the spaces between the tiles, and wipe any excess grout off the tiles, using a clean cloth. Let the grout dry for 24 hours, and then caulk the edges of the tile floor by the walls of the basement.
  
  
• 5). Wait three to four days for the grout and caulk to fully cure. Next, apply a waterproof sealer to the grout and caulk, using a paintbrush. Wipe up any sealer that gets on the tiles.