12×24 is one of the most popular tile sizes in American homes, on floors, shower walls and backsplashes alike. It is also a size that sits right on the line where industry rules change: its 24-inch edge is long enough to trigger the running bond joint minimums in ANSI A108.02. This guide to 12×24 tile grout size answers what grout line to use on floors and walls, in stacked and offset layouts, and when 1/16 inch is realistic. For every tile size and joint in one place, see the tile spacer size chart.
What size grout line for 12×24 tile?
For rectified 12×24 porcelain or ceramic tile, 1/8 inch is the common grout line: narrow but visible, and it meets the ANSI running bond minimum for rectified tile. Calibrated (non-rectified) 12×24 tile in a running bond needs at least 3/16 inch on average. A 1/16 inch joint is possible only with very consistent rectified tile, when the tile maker allows it.
| 12×24 tile | Layout | Grout line (starting point) | Why |
|---|---|---|---|
| Rectified | Running bond or offset | 1/8 inch, plus edge warpage | ANSI A108.02 4.3.8.1 average minimum for rectified tile over 18 inches |
| Calibrated (non-rectified) | Running bond or offset | 3/16 inch, plus edge warpage | ANSI A108.02 4.3.8.1 average minimum for calibrated tile over 18 inches |
| Rectified | Stacked (straight grid) | 1/8 inch; 1/16 inch if the tile maker allows | Size variation and the maker’s minimum decide |
| Calibrated | Stacked | 3/16 inch or as the tile maker specifies | Joint must absorb size variation |
Joint size is only half of it. The joint also has to be at least three times the tile’s actual size range under the proposed ANSI language quoted in LATICRETE TDS 164, and never less than 1/16 inch. Check the box: the tile maker’s minimum joint overrides any general rule.
What size grout joint for 12×24 tile in running bond?
In running bond, 12×24 rectified tile needs an average joint of at least 1/8 inch, and calibrated tile at least 3/16 inch, with the amount of edge warpage added on top. The offset on the 24-inch side should not exceed 33% unless the tile maker specifies otherwise.
Both rules come from ANSI A108.02, quoted in LATICRETE TDS 164. Section 4.3.8.1 gives the joint minimums for tiles with any side greater than 18 inches and its own example: a rectified tile with 1/32 inch warpage on the longest edge needs 1/8 plus 1/32, or 5/32 inch, on average. Section 4.3.8.2 limits the running bond offset to 33% when the side being offset is greater than 18 inches nominal; a larger offset requires an approved mock-up. The reason is warpage: many long tiles are slightly higher or lower in the middle, and a half offset puts the high center of one tile next to the low end of its neighbor. Our article on tile styles prone to lippage shows why offsets matter.
Grout line size for 12×24 floor tile
On floors, 1/8 inch is the safest grout line for rectified 12×24 tile and 3/16 inch for calibrated 12×24. Floors are larger, take side light from windows and doors and rarely match a wall’s flatness, so the extra width absorbs small differences that a tighter joint would show.
Because 12×24 has a 24-inch edge, it is large format tile, and the TCNA flatness guidance in TDS 164 applies: no more than 1/8 inch variation in 10 feet and 1/16 inch in 24 inches. A floor that misses that tolerance will show lippage whatever the joint. See large format tile installation for floor prep.
Grout line size for 12×24 wall tile
On walls, rectified 12×24 tile is often set with 1/16 or 1/8 inch joints. Use 1/16 inch only with very consistent rectified tile in a stacked layout when the tile maker allows it; use 1/8 inch for offset layouts, shower walls and any tile with visible size variation.
Walls are usually flatter and smaller than floors, but shower walls lit from the side show every edge. A stacked vertical layout is a common choice for 12×24 on walls because it avoids the offset warpage problem altogether. For wall-specific setting tips, see using a tile leveling system on walls and showers and our guide to large format wall tile.
Is a 1/16 grout line okay for 12×24 tile?
A 1/16 grout line can work on 12×24 tile only if the tile is rectified, the size variation is very small, the layout is stacked rather than running bond, and the tile maker’s minimum allows it. In a running bond, ANSI A108.02 sets an average minimum of 1/8 inch for rectified 12×24 tile.
Before committing, measure several tiles from different boxes. If the difference between the largest and smallest is more than about 1/64 inch, three times that range already exceeds 1/16 inch. Our guide to the thinnest grout line possible walks through that check, and 1/16 vs 1/8 grout line compares the look.
What size tile spacers for 12×24 tile?
Use spacers or leveling clips that match the grout line you chose: 1/8 inch for most rectified 12×24 tile, 1/16 inch for tight stacked layouts where the tile allows it. Because 12×24 tile is prone to lippage at the long edges, leveling clips are a better choice than loose spacers.
Next Level leveling clips come in 1/32, 1/16 and 1/8 inch and work with reusable wedges. The 1/8 inch clip is the common choice for ceramic and porcelain from 12×12 to large format when you want a narrow but visible line. Place clips along the long edges so they cannot bow between clips; how to use a tile leveling system explains clip placement.
Frequently asked questions
What size grout joint should be used on 12×24 tile in a bathroom?
For rectified 12×24, 1/8 inch on floors and 1/16 to 1/8 inch on walls, following the tile maker’s minimum. Calibrated tile needs more.
Is 12×24 tile large format?
Yes. Its 24-inch edge is over the 15-inch line generally used for large format tile. See what is large format tile.
Can I use a half offset with 12×24 tile?
ANSI A108.02 limits the offset to 33% for sides over 18 inches unless the tile maker specifies otherwise.
Key terms
- Rectified 12×24: 12×24 tile ground to exact size after firing, which allows narrower joints.
- Calibrated 12×24: 12×24 tile sorted into a size range, not ground, which needs wider joints.
- Average joint width: the mean joint across an installation; ANSI minimums for long tile are stated as averages.
- Half offset: a running bond where each tile is shifted by 50% of its length, which magnifies warpage on long tile.
- Third offset: a running bond shifted by about one-third of the tile length, the usual limit for sides over 18 inches.
- Warpage allowance: extra joint width added to the minimum to match the edge warpage of the tile being installed.
- Vertical stack: a wall layout with tiles standing upright in straight columns, without an offset.
Sources
Setting 12×24 tile? Next Level 1/8 and 1/16 inch clips hold the long edges flush while the mortar cures, and the wedges are reusable. The Next Level tile leveling system is sold nationwide by quote. Request a quote for clips for your 12×24 job.