Large-format tile: what it needs before you order

What counts as large format

The tile industry calls a tile large format when any side is 15 inches or longer. That takes in the 12 × 24 inch plank-style tile now common in kitchens, as well as 24 × 24, 24 × 48 and the panels beyond. Above that size, the TCNA Handbook and ANSI A108.02 change several requirements, and each one changes the order.

Flatness: the requirement that decides the job

A large tile cannot follow a wavy floor. It rocks on the high spots and leaves its edge proud of its neighbour, called lippage. For tile with a side of 15 inches or more, the standard asks for a floor flat to within 1/8 inch in 10 ft and 1/16 inch in 2 ft, twice as flat as for smaller tile. Many floors, especially old wood subfloors and slabs, are not.

Check with a straightedge, 6 to 10 ft long, laid in several directions. Mark every gap you can slide a 1/8 inch shim under. Grind high spots; fill low ones with a patch or a self-leveling compound. The self-leveling compound calculator counts the bags: a 120 sq ft area poured to an average 1/4 inch takes about 6 bags, and a whole floor more.

Mortar: deeper notch, both sides

Large tile is set with a 1/2 inch square notch or a slant-notch trowel and usually back-buttered. That is about 1.25 lb of mortar per square foot before buttering, against 0.56 lb for a 1/4 inch notch. Use a mortar rated for large and heavy tile. The thinset calculator adds the buttering, and the thinset guide explains the coverage.

Leveling clips and wedges

A leveling system holds neighbouring tile edges flush while the mortar cures. A clip slides under the tile edges at the joint, and a wedge or cap tightens it down; after curing, the clip snaps off at the joint and the wedges are reused. Makers suggest a clip every 8 to 12 inches along each edge.

The spacers and clips calculator counts clips from the tile size, and the floor tile calculator counts the tile.

Offset: no more than a third

Large rectangular tiles are slightly bowed from the kiln, highest in the middle of the long side. Set in a half offset, the high middle of one tile meets the low end of the next, and the lippage doubles. The standard limits the offset for tile with any side over 18 inches to one third of the tile length, unless the maker approves otherwise. A 24 inch tile is offset 8 inches, not 12.

Layout and cuts

A big tile magnifies a bad cut. A 2 inch sliver of 24 inch tile at a doorway looks like a mistake. Before you order, work out where the cuts fall along both walls and choose between centring a tile and centring a joint. The tile layout calculator compares them: in the 14 × 12 ft kitchen, a centred tile leaves 5.25 inch cuts across the width, and a centred joint leaves 11.2 inch cuts, which look deliberate.

Waste

Large tile wastes more per cut than small tile. An offcut of a 24 inch tile is too large to discard and often too awkward to use, and a single breakage is a large share of the floor. Use at least 10% for a straight layout, 15% in a room with many corners, and keep two or three spare tiles from the same lot for repairs. Check the shade and calibre codes on every box.

Handling and labour

Tiles over 24 inches are heavy and flex when carried flat. They are carried on edge and, at the largest sizes, need two people or suction cups. Labour is slower per tile, though faster per square foot, and many installers charge more for large format. Expect the labour range at the top of the tile figures.

Walls

Large tile on walls brings its own limits. The wall must be flat and plumb, and the backer board is screwed every 8 inches so it does not flex. Heavy tile on a wall is supported from below with a ledger board while the mortar cures, and each row is set on the one below it, never hung. Many makers limit the weight of tile on a wall over gypsum board, and some require cement board for anything over a few pounds per square foot.

Before you buy

1. Measure the floor’s flatness and price the leveling first.
2. Measure a tile from the box; use the real size for the layout.
3. Plan the cuts and the offset.
4. Count the tile, mortar, clips and leveler together.
5. Buy all the tile from one lot, with spares.

The subfloor preparation guide covers what goes under the mortar, and the guide to tile size and grout joint compares large and small tile side by side.