The first lines to plot when laying out a tile floor are perpendicular reference lines. Measure an equal distance (X) from each end of the longer wall and align a laser with these points. Then measure distances Y; if they are equal, the room is square. Otherwise, the lines may have to be adjusted for a balanced layout.

My education in layout began in a large manufacturing and repair shop for machinery. For six months, I was apprenticed to a layout specialist who taught me how to plot accurate layout and machining lines on rough iron castings. Almost 45 years later, I still use the skills I learned on rough castings, applying them to the not-so-perfect floors, walls, countertops, and ceilings I have to cover with tile. Most layouts are simple, with only a few lines required to guide the tiles; but some can be quite complex, requiring a lot of thought, patience, and time to plot.For tile...