How to install 12-inch tile in an unsquare room

Written by darryl brooks
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How to install 12-inch tile in an unsquare room
It's a bit trickier to lay 12-inch tile in an unsquare room, but it can be done with tricks of your own. (Footprints in Tile image by bnstrong from

Any tile floor needs to be installed square or you will have problems. The tiles are square and the joints are small, so adjusting an out-of-square installation is difficult. This is worse with larger tiles such as a 12-inch tile. Keeping the tile square in an out-of-square room is challenging because you don’t have anything to guide you. There are two things you can do to help. Find a square corner or the least out-of-square corner, and run the tile in a pattern that will help hide the fact that the room is not square.

Skill level:

Things you need

  • Measuring tape
  • Type II floor tile adhesive
  • Notched trowel
  • Straight edge
  • Ceramic tile
  • Tile spacers
  • Tile cutting machine or wet saw
  • Grout pad
  • Grout
  • Sponge

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  1. 1

    Measure each of the corners opposite the door you need to back out of to determine which is square or closest to it. An out-of-square room may have one square corner. You will use a 3-4-5 ratio to determine this. If you measure and mark a spot from the corner a multiple of three on one wall and four on the other, the distance between the two will be five if the corner is square. It doesn’t matter if it is three feet, three yards or thirty inches as long as the ratio is the same. Use the longest measurement that will fit the room for the most accuracy. The corner that is square or closest to it will be the one to start in.

  2. 2

    Start spreading the adhesive from the corner you chose using the notched trowel. Force the glue into the floor with the flat side of the trowel to achieve a good bond and then comb back through it with the notched side. Spread a section slightly more than two feet from the back wall.

  3. 3

    Begin laying whole tile in the corner and down the back wall using tile spacers to keep the joints even. On the second row, start with a half tile and then continue the rest of that row. Check the tiles with the straight edge to make sure you are starting off perfectly straight. Continue backing across the room in this fashion, alternating starting with whole and half tiles and checking the tiles every two or three rows with the straight edge. The staggered joints will help hide the fact that the room is out of square. Let the glue dry for at least 24 hours.

  4. 4

    Mix up some grout following instructions on the bag and spread it using the grout pad. Smear it across the tiles and force it into the joints so they are full. Use the edge of the pad to pull excess grout from the tiles. Use a damp sponge to wipe all excess grout from the face of the tiles while smoothing the grout joints. Allow the grout to dry to a haze and wash a second time with clean water. After it dries again, the haze should buff off easily with a dry towel.

Tips and warnings

  • When selecting a tile cutter, make sure it can handle 12-inch tiles. Since this installation will require more cuts than normal, you may want to invest in the wet saw.
  • Have someone at the tile store show you how to use the tile cutter or wet saw.
  • Even though you may be installing the tile in an out-of-square room, your tiles themselves still need to be perfectly straight. Use the straight edge often.

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