Large format tile installation follows the same basic steps as any tile job, but each step has less room for error. The floor has to be flatter, the mortar coverage fuller, the trowel bigger and the layout smarter. Get those right and 24×48 porcelain goes down flat and solid; miss one and you get hollow spots, cracked corners or lippage. This guide walks through installing large format tile on floors and walls, including showers. If you are choosing the spacers or clips for big tile, clip spacing and joint size are covered in large format tile spacers and leveling clips.
What qualifies as large format tile?
Large format tile is generally any tile with at least one edge 15 inches or longer. NTCA’s TileLetter describes tile over 15 inches on one side as generally accepted as large format, and TCNA’s stricter flatness requirement applies from 15 inches. So 12×24 counts, and so do planks and slabs.
The definition matters because it triggers tighter rules for substrate flatness, mortar, and layout. Very heavy pieces are often called large and heavy tile and need mortar rated for them.
What size is large format tile?
Common large format tile sizes are 12×24, 24×24, 24×48, 32×32, 36×36 and 48×48 inches, plus planks like 8×48 and porcelain slabs and gauged panels much larger than that. Anything with an edge of 15 inches or more falls in the group.
| Size | Where you see it | Installation notes |
|---|---|---|
| 12×24 | Floors, shower walls | Watch the offset on long edges |
| 24×24 | Floors, open living areas | Needs a flat floor and full coverage |
| 24×48 | Floors, feature walls | Two-person lift, back-butter every piece |
| Planks (6×36, 8×48) | Wood-look floors | Offset 33% or less; clip long edges |
| Slabs and gauged panels | Walls, countertops, floors | Separate standards, special handling |
How flat does the floor need to be for large format tile?
For tile with any edge 15 inches or longer, the substrate should vary no more than 1/8 inch in 10 feet and no more than 1/16 inch in 24 inches from the required plane. For smaller tile, the limit is 1/4 inch in 10 feet. Measure from the high points.
These figures come from TCNA guidance quoted in LATICRETE TDS 164 and repeated by NTCA’s TileLetter. Check with a long straightedge or laser in several directions. Grind high spots, fill low spots with patch or self-leveling underlayment, and recheck. On wood-framed floors, stiffness matters too: the TCNA Handbook limits deflection for ceramic tile floors to L/360. Over cracked slabs, a crack isolation membrane can protect the tile from small movement.
What trowel size for large format tile?
The right trowel for large format tile is the one that gives full coverage: at least 80% in dry areas and 95% in wet areas and exteriors. Large notches, often 1/2 inch square or U-notch and larger, are common, but always confirm by lifting a tile and looking at the back.
Comb the mortar in straight, parallel ridges, not swirls. Directional troweling, with ridges running the same way across the floor and the tile pressed in with a slight slide across them, lets air escape and helps ridges collapse. A mortar coverage check every few tiles tells you whether the trowel notch size, mortar mix and setting pressure are working. Coverage figures are from NTCA’s TileLetter.
Large format tile mortar vs regular thin-set
Large format tile mortar is formulated to be applied thicker without slumping and to support heavy tile, while regular thin-set is designed for thinner beds. Using regular thin-set too thick can let large tile sink unevenly as it cures, causing hollows and lippage.
Look for mortar labeled for large and heavy tile, sometimes called medium-bed mortar, and follow the bag for mixing, open time and maximum bed thickness. Do not use extra mortar to fix a bad floor; that is one of the main causes of lippage listed in LATICRETE TDS 164.
Do you need to back-butter large format tile?
Yes. Back-butter large format tile by skimming a thin coat of mortar onto the back with the flat side of the trowel. It fills the tile’s back pattern, improves bond, and helps you reach full coverage, especially at the corners and edges.
Spread the floor mortar, back-butter, set the tile with a slight slide perpendicular to the ridges, then bed it with a beating block or vibration tool. Place leveling clips on each edge as you go.
How do you install large format tile on a shower wall?
On a shower wall, start from a level ledger, use a non-sag mortar rated for large tile, back-butter every piece, aim for 95% coverage because it is a wet area, and use leveling clips on every joint. Plan the layout so cuts are balanced and niche edges fall on grout lines.
Large tile on a sloped shower floor is harder: the slope toward the drain is a curved or multi-plane surface, and a flat tile cannot follow it. LATICRETE TDS 164 notes that the standard lippage chart does not apply to floors sloped to drains and that smaller tiles reduce lippage in sloping areas. A linear drain with a single-plane slope makes large tile on a shower floor more practical. Wall-specific tips are in using a tile leveling system on walls and showers.
How do you avoid lippage on large format tile?
Avoid lippage on large format tile by flattening the substrate, getting full coverage, keeping running-bond offsets at 33% or less for tiles over 18 inches, choosing a joint wide enough for the tile’s warpage, and using a tile leveling system on every edge while the mortar cures.
The 33% LFT offset limit comes from ANSI A108.02 section 4.3.8.2 unless the tile maker specifies otherwise. A tile leveling system for large format tile, such as the Next Level clips and reusable wedges, holds neighboring edges flush until the mortar sets. Clip spacing and joint choice for big tile are covered in large format tile spacers and leveling, and the full list of causes is in what is tile lippage. For porcelain-specific steps, see porcelain tile installation.
Frequently asked questions
What grout spacing is used for large format tile?
Commonly 1/16 to 1/8 inch for rectified tile; ANSI calls for at least 1/8 inch on average for rectified tile over 18 inches in running bond.
What tools do you need for large format tile installation?
Large-notch trowel, mixing drill, straightedge, leveling clips and wedges, a wet saw or long rail cutter, suction cup lifters, and a helper. See tile leveling tools.
Is large format tile harder to install than small tile?
It is less forgiving. Fewer joints means less to grout, but flatness, coverage and handling must all be right.
Key terms
- Directional troweling: combing mortar ridges in one straight direction so air escapes when the tile is set.
- Trowel notch size: the width and depth of a trowel’s notches, which controls how much mortar goes down.
- Flatness 1/8 in 10 ft: the substrate flatness tolerance for tile with any edge 15 inches or longer.
- Crack isolation membrane: a sheet or liquid layer that keeps small substrate cracks from transferring into the tile.
- Shower pan slope: the pitch of a shower floor toward the drain.
- Mortar coverage check: lifting a freshly set tile to see how much of its back is in contact with mortar.
- LFT offset limit: the 33% maximum running-bond offset for tiles over 18 inches unless the tile maker specifies otherwise.
- Two-person lift: carrying and placing large tile with two people to avoid flexing and cracking it.
Sources
- LATICRETE TDS 164, Lippage: Causes and Prevention (TCNA flatness, ANSI A108.02 4.3.8.2, sloped floors)
- TileLetter (NTCA), Large-format tile: know your numbers for installation success
- TileLetter (NTCA), Meeting the required L/360
Installing large format tile? Next Level ships clips in 1/32, 1/16 and 1/8 inch with reusable wedges nationwide, sold by quote. Request a quote for large format leveling clips. See the clip size chart to estimate quantities.