Establish a reference
To create a layout grid, you need to know the size of the tiles. This determines the size of the grid squares. From there, you can establish horizontal and vertical reference lines, and superimpose the grid on the floor.
I start by laying a few tiles side by side along a straightedge, each separated by the width of the grout joint that I plan to use, and then measuring the length of the group plus a line of grout on one outside edge. I’m aiming for a unit of measure that’s between 24 in. and 36 in., a distance I can comfortably reach on a typical floor installation.
Once I determine the unit measurement, I snap a reference chalkline parallel to the longest straight wall in the room. That reference line can be any distance from any wall, including a centerline between two main walls, or the reference line can be the cumulative measurement of tiles and grout joints from a single wall.
Next, I measure from that line to various stops, such as walls, entryways, and cabinet bases, to determine the cuts I’ll have. I always plan for at least half a tile at the most obvious places—doorways and long, visible walls, for example. In some cases, it’s impossible to have large pieces everywhere, so I place narrow pieces in closets, under cabinet toe kicks, or behind toilets.
If my first reference line doesn’t give me a layout that works, I erase the line with a damp sponge, adjust the location, and snap a new one. Then I snap lines at the unit-measure increments parallel to my reference line. It’s critical to make sure the measurements are precise; a 1⁄4-in. or even 1⁄8-in. error can throw off the entire layout.