How to Lay Out a Ceramic Tile Floor

Planning the layout of your tile floor is an essential step in guaranteeing the success of your project. Ever wonder how a professional tile layer always seems to get those tiles at a perfect 90- or 45-degree angle to the wall? You can do it, too, and here’s how.

Install ceramic tile over a subfloor that’s no less than 1 1/8 inches thick. A thinner subfloor will cause the floor to flex due to the weight of the tile. A flexing subfloor results in cracked tiles and grout — and a lot of headaches. Most tile manufacturers recommend installing a cement backer board instead of any other type of underlayment, such as plywood. The boards come in 3-by-5-foot sheets and are available where tile and grout are sold.

Begin planning by using a pair of perpendicular reference lines for establishing your layout instead of relying on measurements from walls, which are neither straight nor square to each other. To ensure the reference lines are square, use a 3-4-5 triangle rule as follows:

1. Establish your first reference line by measuring across opposite sides of the room. Mark the center of each side and then snap a chalk line between the two marks.

2. Measure and mark the center of that line. Then use a pencil, a framing square, and a straightedge held against its shorter leg to mark a second 4-foot-long line perpendicular to the first line.

   Before snapping a second line across the room, you want be sure the angle you formed is truly 90 degrees.

3. Measure out 3 feet from the intersection and mark the penciled line. Then measure out 4 feet from the intersection and mark the spot on the chalk line. Measure the distance between the 3-foot and 4-foot marks.

   The distance should be 5 feet — the 3-4-5 rule. If it isn’t, make an adjustment and pencil a new line. Now snap a chalk line across the room that falls directly over the penciled line.

After you have reference lines, use them to establish layout lines, which actually guide tile placement. Dry-set two rows of tiles, extending from the center to adjacent walls. If the last tile in a row would be less than half a tile, plan to shift the first course to be centered on the reference line rather than next to it. Snap your layout line a half line away from the reference line. Repeat the procedure for the other row.

Laying out your tiles at 45-degree angles instead of 90 isn’t that difficult. You need only a couple more layout lines. Mark the two layout lines as you would for a 90-degree job and then follow these steps:

1. Measure out the same distance (for example, 4 feet) on the perpendicular lines.

2. From these points, make marks 4 feet out at right angles to the original lines.

3. Snap a chalk line through these new marks and through the intersection of the two original layout lines.

   The two lines are now your layout lines for a 45-degree pattern.