In Faux Wood Tile Sophistication, we mentioned how important it is to pay attention to offsets when installing tile. The reason? For managing lippage.
Tile Size Affects Tile Installation
Offsets and grout joints are particularly critical when you are installing larger tile sizes and rectangular tile such as a wood plank tile where the length is much greater than the width. Since tile is trending larger, it's important to understand how size affects tile installation so you have a floor that meets your expectations for lippage and truly delights you forever.
In this article, we'll review how to properly manage lippage when installing large-format pressed tiles.
What Is Lippage When You Are Installing Tile?
According to Wiktionary, lippage is "an uneven surface of a floor that occurs when stone or tiles are not laid to a uniform level." If you look at the image above, notice how some tiles seem higher than others? That's an extreme case of lippage. The tile planks don't form a flat surface.
Lippage happens. It's a function of how different in thickness one tile is compared to the other, the spacing or grout line between the different tiles, how the subfloor has been prepared as well as whether the tile itself has any minimal warpage. Minimal warpage is frequent in larger sized tiles; it results from the manufacturing process and should be expected with kiln-fired clay products.
However, it's important for lippage not to become excessive and affect the integrity of the tile installation. Be sure to read the Tile Council of North America's (TCNA) explanation of lippage which describes the ANSI standards for allowable lippage and warpage.
Since lippage happens, it's important to know how to manage lippage when installing tile.
Managing Lippage in Tile: Pay Attention to Offsets!
The most effective way for managing lippage - especially when you're installing large format tile as we detailed above - is by paying close attention to how tiles are offset from one another during installation.
"Large rectangular tiles are pressed with inherent tension, this strengthens shape, similar to tensioned concrete slabs or flat heavy haul trailers. This strengthening begins to develop during the pressing of the tiles and continues to develop in the tile as it passes on to the drying oven. The resulting tension in pressed rectangular tiles can sometimes show in the form of an arc or crown on the surface of the tile. While completely within ANSI 137.1 specifications, these large rectangles can require the following:
- Shifting the tile pattern
- Change in installation method and setting mortar
- Both may be necessary, particularly if a very narrow grout joint is expected."
Traditional Offset TCNA recommendation
The article then explains how, modifying the traditional 50% offset used in a brick pattern (see diagram above) to a maximum of 33% - which doesn't affect the look of the pattern - when installing tile 18" or larger, will manage lippage.
"The above 1/3 offset is now the prevailing recommendation from the Tile Council of North America 2011 for ALL tile 18” or longer."
In terms of the recommended installation method, the article states:
"The use of a larger notch trowel, in conjunction with a medium bed or full contact mortar is recommended to improve overall support and coverage for large tile modules. Gently opening up the grout joint will also improve transitions from tile to tile. The TCNA Handbook 2011 page 33 recommends for tile “with any side 18” or longer the grout join shall be, on average, a minimum of 1/8” wide for rectified tiles and, on average, a minimum of 3/16” wide for calibrated (non-rectified) tiles."
What Are Some Tile Installation Challenges Associated With Offsets To Manage Lippage?
In a January/February 2010 Tile Magazine article titled Rectangular Tiles: How to “Offset” Certain Installation Challenges (pdf), Bill Griese, Standards Development and Green Initiative Manager for the Tile Council of North America, answers several questions about challenges associated with offsets when installing tile.
1. Rectangular tiles can present a challenge with offsets:
"Manufacturers strive to produce perfectly flat tiles, but when that’s not possible, they opt to produce tiles that are slightly “domed.” While such curvature is usually minimal, any time the center of one tile is beside the edge of another, there could be lippage. Also, because the length and width are different on rectangular tiles, flat installations can be a challenge when any substrate unevenness occurs, especially when the unevenness is along the tile’s longer edge.
The challenge is particularly relevant to very large rectangular tiles, such as with dimensions of 24” x 48”. The solution:
"That being said, very large rectangular tiles are installed successfully every day when suitable arrangements for a flat substrate have been made and the critical design issues: grout joint width, type of lighting, and amount of offset, have been properly considered and addressed."
2. Offset and modular patterns can present an installation challenge.
Some tile installation patterns are based on not installing tile where all of the grout lines align. Rather they stagger the tiles as in the photo above and the diagram.
"... problems are most common when 50% offsets are used, or wherever the center of one tile is beside the end of another. When such is the case, even minimal warpage can create lippage, because the highest point on the surface of one tile is directly beside the lowest point on another."
In the case of modular patterns, Griese explains, you may need to vary the grout line recommendations:
"A modular pattern is any pattern where multiple sizes are used in a repeating combination, for example when 24” x 24” tiles are installed with 12”x24”, 12”x12”, 6”x12”, and 6”x6” tiles. In such a pattern, the center of the rectangular tiles regularly lines up next to the edge of the square tiles. Typically, each modular pattern comes with a recommended grout width from the manufacturer for all the tiles to line up. While these patterns are precisely calculated, all too often they are specified with grout joints that are too narrow to minimize the effects of any warpage or installation related lippage. While such patterns can be very appealing, with many imported tiles, they may require varying and larger grout widths than specified by the manufacturer to achieve the most attractive installations with the least lippage.
3. Is there a way to reduce noticeable lippage in an offset or modular pattern tile installation?
Let's say you have a large tile which pushes the edge on acceptable warpage (i.e., it shows maximum allowable warpage) and you have your heart set on an offset or modular pattern tile installation. What can you do to reduce lippage?
Avoid patterns with offsets in excess of 33%
Griese suggests the following in terms of offsets:
"For large tiles exhibiting the maximum allowable warpage, 50% offsets are guaranteed to exhibit lippage. To address this on a practical basis, some manufacturers recommend against any patterns with offsets in excess of 33%, if the tile being used has an edge larger than 18 inches. When considering large tiles and offsets greater than 33%, consumers are encouraged to consult with manufacturers for specific recommendations. Most cases you are able to find this information on the actual tile box."
Avoid narrow grout joints
"For all tile installations, but especially ones with offset patterns, extra precautions should be taken if a narrow grout joint is desired. A narrow grout joint is generally considered to be less than 1/8 of an inch. While rectangular tiles are often rectified, or ground to precise sizing, such grinding does not remove any warpage that is present. Even slight lippage caused by minimally warped tiles can become increasingly noticeable as grout joints get smaller. When opting for an offset pattern, it is important to consider a wider grout joint to reduce noticeable lippage."
Light can accentuate visible lippage
Another important consideration when installing large tile is the direction of light, as light can accentuate visible lippage.
"With artificial lighting, it’s best to move lights away from the wall. With natural lighting, it’s best to orient patterns such that offsets are not perpendicular to the direction of late afternoon or early morning lighting."
Final Advice for Managing Lippage
Finally, don't ever underestimate the importance of preparing the subfloor and ensuring the substrate is level for reducing noticeable lippage.
Be sure to select the right mortar for the specific installation and set the right expectations for lippage given the tile used and the type of offset needed.
Here are a few more resources on managing lippage:
How Have Offsets Helped You with Managing Lippage?
Have you encountered a situation where the offset you used in your tile installation helped prevent excessive lippage?
What advice would you add to this article?
Thanks for reading!
Note: This article was originally published on February 25, 2016 and has been updated.