Big tile is unforgiving. A 24×48 porcelain tile spans more floor, bows more along its length and is usually set with a tight joint, so any difference in height between two pieces shows up as a long shadow. Plain spacers keep the gap even, but they do nothing about height. This guide covers large format tile spacers and leveling: what counts as large format, how to space clips, which joint suits big porcelain, how flat the floor must be, and what changes with thin porcelain panels. For the full install process (trowel, mortar, back-buttering and shower walls), see large format tile installation, step by step.
What counts as large format tile?
Large format tile, or LFT, is generally any tile with at least one edge 15 inches or longer. That includes 12×24, 24×24, 24×48 and plank tile. Tile that is also very heavy is often called large and heavy tile, or LHT, and needs mortar rated for it.
The 15-inch threshold matters because it is where the industry’s substrate flatness requirement gets tighter. NTCA’s TileLetter notes that tile over 15 inches on one side is generally accepted as large format, and TCNA guidance quoted by LATICRETE uses “at least one edge 15 inches in length” for the stricter flatness rule. A 12×24 tile already falls in that group.
Why is large format tile hard to set flat?
Large format tile is hard to set flat because it bridges the highs and lows in the floor, it has more length to warp, it needs fuller mortar coverage, and it is usually set with a narrow joint that hides nothing. Each of these turns small errors into visible lippage.
A small tile rides up and down with the floor; a long one rests on the high spots and leaves hollows under the rest. Porcelain also has a natural bow from firing, and on a long tile that bow is larger in absolute terms. Combined with the wrong offset, the high center of one plank ends up next to the low end of the next. See what is tile lippage for the full list of causes.
How far apart should leveling clips be on large format tile?
On large format tile, place clips near every corner, a couple of inches in from the end, and add clips along long edges so the edge cannot bow between them. Thin, long or noticeably warped tile needs closer clip spacing than thick, flat tile.
| Tile | Starting clip layout |
|---|---|
| 12×24 | Two clips on each long edge, one on each short edge |
| 24×24 | Two clips per shared edge, near the corners |
| 24×48 | Clips near each corner plus extra along the 48-inch edges |
| Plank tile (8×48, 6×36) | Clips near the ends plus extra along the long edges |
| Thin porcelain tile | Closer spacing on every edge; follow the tile maker |
Treat this as a starting point and tighten spacing where a straightedge shows the edge moving. Clip counts per square foot by size are on the tile leveling clip size chart. A tile leveling system for large format porcelain such as Next Level holds each edge flush while the mortar cures.
Which grout joint suits large format porcelain?
Rectified large format porcelain is commonly set at 1/16 to 1/8 inch. For tiles longer than 18 inches in a running bond, ANSI A108.02 calls for an average of at least 1/8 inch for rectified tile and 3/16 inch for calibrated tile, plus the tile’s edge warpage.
That rule is in ANSI A108.02 section 4.3.8.1, as quoted in LATICRETE TDS 164. Stacked layouts with very flat rectified tile can go tighter if the tile maker allows. For Next Level, 1/8 inch is the common joint for ceramic and porcelain from 12×12 to large format when you want a narrow but visible grout line. Compare options in 1/16 vs 1/8 grout line.
How flat does the floor need to be?
For tile with any edge 15 inches or longer, TCNA guidance allows no more than 1/8 inch variation in 10 feet and no more than 1/16 inch in 24 inches from the required plane. Smaller tile allows 1/4 inch in 10 feet. Fix the floor before tiling; mortar is not a leveler.
Check with a long straightedge or laser. Grind high spots and fill low ones with a patch or a self-leveling underlayment. Trying to build up low spots with extra thin-set under each tile is one of the main causes of lippage, according to LATICRETE TDS 164. Clips keep neighboring edges flush; they do not make a wavy floor flat.
Do you need special mortar for large format tile?
Usually yes. Large format tile is typically set with a mortar labeled for large and heavy tile, sometimes called a medium-bed or LHT mortar, which can be applied thicker without slumping. Coverage targets are 80% in dry areas and 95% in wet areas and exteriors.
Those coverage figures come from NTCA’s TileLetter. To reach them, comb straight ridges, back-butter the tile, and press it in with a slight slide so the ridges collapse. Some installers use a vibration tool to help the tile bed in. Full installation steps are in large format tile installation.
What about thin porcelain panels?
Gauged porcelain tile and panels, often 6 mm or thinner and up to slab size, follow their own installation standards and tighter lippage limits. ANSI A108.02, as reported by LATICRETE, allows 1/32 inch of lippage for gauged porcelain at any joint width.
Thin panels flex, so they need near-perfect substrate flatness, full coverage and careful handling. Installers move them with a tile handling frame or suction cup lifters to avoid cracking. Check that your leveling system is rated for the panel thickness; the Next Level product page lists tile from 1/4 to 7/16 inch thick, so very thin panels may fall outside that range.
Frequently asked questions
Do large tiles need spacers?
Yes. Large tiles need something to hold an even joint, and leveling clips do that while also keeping edges flush.
Why does 12×24 tile get lippage?
Because 12×24 is long enough to bow and is often set at a 50% offset, which lines up high and low spots. Use a 33% offset or less and clip the long edges.
What is the best tile leveling system for large format tiles?
One rated for your tile thickness, with a clip in your joint width and enough clips to support long edges. See how to choose a tile leveling system.
Key terms
- Large format tile (LFT): tile with at least one edge 15 inches or longer.
- Large and heavy tile (LHT): large format tile heavy enough to need mortar rated not to slump under it.
- Gauged porcelain panel: a thin, large porcelain sheet made to a specified thickness, installed under its own standard.
- Thin porcelain tile: porcelain thinner than standard tile, which flexes and needs close support.
- 12×24: a 12 by 24 inch tile, the most common entry size for large format.
- 24×24: a 24 inch square tile used on floors and walls.
- 24×48: a 24 by 48 inch tile that demands very flat substrates and full mortar coverage.
- Plank tile: long, narrow tile, often wood-look, such as 6×36 or 8×48.
- Medium-bed mortar: a mortar that can be applied thicker than standard thin-set without slumping.
- LHT mortar: mortar labeled for large and heavy tile.
- Floor flatness tolerance: the maximum allowed deviation of the substrate from a flat plane over a given distance.
- Self-leveling underlayment: a pourable cement product that flows out to create a flat surface before tiling.
- Vibration tool: a handheld vibrating pad that helps bed large tile into mortar.
- Mortar ridge collapse: the flattening of troweled ridges into a continuous layer when the tile is pressed in.
- Slab tile: very large porcelain sheets, often several feet on a side.
- Tile handling frame: a rigid frame with suction cups for carrying large panels without bending them.
- Suction cup lifter: a handheld suction tool for lifting and placing large tile.
Sources
- LATICRETE TDS 164, Lippage: Causes and Prevention (ANSI A108.02 and TCNA tolerances)
- TileLetter (NTCA), Large-format tile: know your numbers for installation success
Setting big tile soon? Next Level ships leveling clips and reusable wedges nationwide, sold by quote. Request a quote for large format leveling clips with your tile size and square footage.