Large format

Large format is a size, not a grade. The line is any tile with one edge of 15 inches or more, where the installation standard ANSI A108.02 starts asking for a flatter floor underneath. Porcemall's 24 by 48 is past it, and so are 48 by 48 and a 9 by 60 plank.

One piece covers close to eight square feet, and that is why it behaves differently. A small tile floor has a joint every few inches, and each joint absorbs a little of whatever the base is doing. A large floor has far fewer of them. The body is no weaker. The piece is simply long enough now to bridge a low spot instead of following it.

Lippage is the height difference between the edges of two tiles that sit next to each other. You see it as a shadow line along a joint and catch it with a bare foot. ANSI A108.02 sets the allowance as a fixed figure plus whatever warpage the tile is permitted under ANSI A137.1. Joint width decides the figure.

A narrow joint buys less room, not more. Rectified tile, listed under Edge on every product page, is ground to size after firing, so its edges are straight and it takes that narrow joint. It is why a rectified floor reads as one surface, and why no margin is left. A wide joint gives the eye a band between two tiles; a narrow one hands it a continuous plane, where any step shows. Joint width is in grout and trim.

Lippage is mostly decided before a tile leaves the box. ANSI A108.02 sets how flat the substrate has to be, and the tolerance tightens as the tile gets longer.

The allowance across ten feet is halved for the format Porcemall sells most. A 24 by 48 tile spans close to four feet on its own, so whatever the floor does across that run the tile has to do too. If it cannot, an edge lifts.

Getting a slab there is patching and self levelling compound, before setting day. Mortar cannot fix it. Extra thinset under a low spot leaves a soft bed that shrinks as it cures and lets the tile settle back down.

A long tile is not perfectly flat, and it is not meant to be. It leaves the kiln with a slight bow along its length, usually crowned, so the middle sits a little higher than the ends. On a 60 inch plank that bow is within tolerance and unavoidable.

Lay two of those planks at a half offset. The middle of one tile, its highest point, arrives beside the end of its neighbour, the lowest point. The pattern has put the two extremes of the bow against each other, and the difference is lippage, along the line the eye already follows. At a third or less, the point meeting that end sits nearer its own end, where the bow has flattened out.

The TCNA Handbook makes it a recommendation: for tile with any side over 15 inches, keep a running bond offset to no more than one third, and consult the manufacturer before going further. Customers ask for a half offset because that is how a wood floor is laid. A wood plank flexes under a nail or a click joint. A porcelain plank does not.

Four things an installer does differently here. None is exotic. All are slower.

Flat base first, pattern second, technique third. An installer fighting lippage with clips lost that argument at the start of the day. The stages are in installation basics.