Thin grout lines are popular for a simple reason: the less grout you see, the more the tile looks like one continuous surface. But every tile has a limit, and pushing past it creates crooked joints, visible lippage and grout that will not fill properly. This guide answers how thin a grout line can really be, how to tell whether your tile can take a tight joint, which grout works in narrow joints and how to set the joint with clips. For a side-by-side look at the two most common joints, see 1/16 vs 1/8 grout line.
What is the thinnest grout line possible?
The thinnest grout line possible in practice is about 1/32 inch (1 mm), and only with precisely rectified tile when the tile maker allows it. For most installations, industry guidance sets 1/16 inch (1.5 mm) as the minimum, and the joint must also be wide enough for the tile’s real size variation.
Two rules decide the limit. The first is the tile maker’s minimum joint, printed on the box or in the product literature; it overrides any general guidance. The second is the proposed ANSI language quoted in LATICRETE TDS 164: the actual grout joint should be at least three times the actual range of facial dimensions of the tile supplied, and in no case less than 1/16 inch. A 1/32 inch joint therefore sits below the general minimum and belongs only to tile made for it.
What is the smallest grout line for floor tile?
For floor tile, the smallest grout line is usually 1/16 inch with rectified tile, and many floor tile makers specify 1/8 inch or more. Long tiles in a running bond have their own minimum: ANSI A108.02 calls for an average of at least 1/8 inch for rectified tile with any side over 18 inches.
Floors are harder on thin joints than walls. They are larger, they see side light from windows and doors, and the substrate rarely matches a wall’s flatness. Section 4.3.8.1 of ANSI A108.02, quoted in TDS 164, also requires adding the amount of edge warpage to the minimum: a rectified tile with 1/32 inch warpage on its longest edge in a running bond needs about 5/32 inch on average, not 1/8. On walls, small glazed tile and mosaics can run joints from 1/16 to 1/8 inch under the ANSI lippage chart.
How do you know if your tile can take a thin grout line?
Measure several tiles from different boxes and find the difference between the largest and smallest. Multiply that range by three: the result is the narrowest joint the proposed ANSI rule supports. Then compare it with the tile maker’s minimum and use whichever is wider.
| Measured size range across tiles | Three times the range | Practical joint |
|---|---|---|
| Under 1/64 inch (very precise rectified) | Under 3/64 inch | 1/16 inch minimum; 1/32 inch only if the tile maker allows |
| About 1/32 inch | About 3/32 inch | 1/8 inch |
| About 1/16 inch | 3/16 inch | 3/16 inch (the example given in TDS 164) |
Measure along the same edge on each tile with a good tape or caliper, and check squareness by laying tiles together. Rectified tile, which is ground to size after firing, is the only realistic candidate for a hairline joint; calibrated tile varies too much. Our guide to rectified tile explains the difference.
What grout works in a thin grout line?
Narrow joints need a grout rated for their width. Unsanded grout is made for joints of 1/8 inch or less. Some sanded grouts are rated down to 1/16 inch and others start at 1/8 inch, and epoxy grouts list their own range. Read the joint range on the bag before you buy.
LATICRETE states that its sanded grouts can be used in joints 1/16 inch or wider and its unsanded grout only in joints 1/8 inch or less. By contrast, CUSTOM’s Polyblend Plus Sanded Grout is rated for 1/8 to 1/2 inch joints. Two sanded grouts, two different minimums, which is why the bag matters more than the category. TDS 164 also warns that joints that are too narrow can make it hard to fill the joint fully and to keep it clean. For grouting technique in tight joints, see how to grout tile, step by step.
Why do thin grout lines show lippage?
A thin grout line leaves nothing to soften a height difference between tiles. With a wider joint, the eye reads the grout as a break; with a 1/16 or 1/32 inch joint, a raised edge throws a sharp shadow, especially in raking light. LATICRETE notes that tight joints make warpage and substrate problems much more noticeable.
That is why thin joints and a leveling system go together. The ANSI lippage chart in TDS 164 already holds narrow joints to tight tolerances, such as 1/32 inch lippage for glazed wall tile and mosaics with 1/16 to 1/8 inch joints. Learn more in what is tile lippage.
Grout spacing: how do you set a thin joint?
Set thin joints with leveling clips sized to the joint, not with loose spacers. The clip tab fixes the grout spacing at every edge, and the wedge holds both tiles in the same plane while the mortar cures, which is what a thin joint needs.
Next Level makes leveling clips in 1/32, 1/16 and 1/8 inch for ceramic and porcelain tile. Use the 1/32 inch clip only where the tile maker allows a joint that narrow, since the common industry minimum is 1/16 inch. For most ceramic and porcelain tile from 12×12 to large format, 1/8 inch is a common choice when you want a narrow but visible grout line. The clip size chart matches each size to tile types, and the tile leveling system FAQ covers common questions.
Can you install tile with no grout lines?
No. Setting tile edge to edge with no joint, called a butt joint, is not recommended: the proposed ANSI language says the joint should never be less than 1/16 inch, and a butt joint leaves no room for size variation or movement. Panels and slabs reduce grout lines by being larger, not by removing the joint.
Movement is the hidden problem. TDS 164 points out that very narrow grout joints can create visual problems where movement joints, which are often wider, have to run through the installation.
Frequently asked questions
Is a 1/32 grout line too small?
For most tile, yes. It is only for precisely rectified tile when the tile maker allows it.
Do thin grout lines crack more?
A grout used outside its rated joint range can crack or fail to fill. Use a grout rated for your joint width.
What is the thinnest grout line for wood-look plank tile?
Long planks in running bond need at least 1/8 inch on average if rectified, plus any edge warpage, under ANSI A108.02.
Key terms
- Smallest grout line: the narrowest joint a specific tile can support, set by its size variation and its maker’s minimum.
- Three-times rule: proposed ANSI guidance that a grout joint be at least three times the tile’s actual size range.
- Size range: the difference between the largest and smallest tile in the batch you are installing.
- Minimum joint width: the narrowest joint allowed by the tile maker or the standard, whichever is wider.
- Grout spacing: the gap left between tiles for grout, set by spacers or leveling clips.
- Tight joint: an informal name for a narrow grout joint, usually 1/16 inch or less.
- Caliper: a measuring tool used to compare tile sizes precisely before choosing a joint.
Sources
- LATICRETE TDS 164, Lippage: Causes and Prevention (proposed ANSI joint rule, ANSI A108.02 4.3.7 and 4.3.8.1)
- LATICRETE, cement grout FAQ (sanded and unsanded joint ranges)
- CUSTOM Building Products, Polyblend Plus Sanded Grout data sheet (1/8 to 1/2 inch joints)
Going for a tight joint? Next Level clips set 1/32, 1/16 or 1/8 inch grout spacing and keep edges flush, which a thin joint demands. The Next Level tile leveling system ships nationwide by quote. Request a quote for clips in your joint size.