1/8 in.
in 10 ft, the flatness limit for large-format tile
Flat Floors Before Big Tile
Large porcelain panels and long wood-look planks turn every dip in the floor into a raised edge, called lippage. ANSI A108.02 limits the substrate for large-format tile to 1/8 inch in 10 feet, half the allowance for standard tile. We check the slab with a straightedge, grind and level until it meets that number, and use a tile leveling system on big pieces so neighboring edges stay even while the thinset cures.
