Flooring Forensics: Ceramic tile and stone—the other hard surfaces - July 2021

By Lew Migliore

Ceramic tile and stone may be thought to have taken a back seat to luxury vinyl tile and plank, but they can’t be relegated as the stepchild of flooring. These types of floors have been around since the beginning of the civilized world, and their longevity is legendary. No other flooring has survived the centuries of use and generations of mankind. No other flooring material is as durable, and few are as natural and environmentally friendly. Stone is as it sounds: a material taken directly from the earth. Ceramic tile is made from clay and is fired in a kiln.

For commercial applications, you can see tile in the lobbies or entries to most office buildings due to its durability, beauty, longevity, appearance retention and relative ease of cleaning. Residentially, there is more tile and stone used in warmer climates of the United States than in colder ones, but with underfloor heating systems, these floors can be used and enjoyed anywhere. Another factor for accepted use in a residential setting is whether the house is built on a slab, which makes a perfect substrate for tile installation.

Ceramic tile can be made to look like most anything while stone is, well, stone, and looks like what it is, such as marble and granite. What it looks like when quarried from the earth is what you get, that natural beauty. Porcelain is one of my favorite flooring materials of all time, and it continues to increase in style, color and beauty.

Ceramic floor tiles can be damaged by caustic chemicals. I stay in a lot of hotels around the country and often see the effects of these chemicals on ceramic, especially in and around the toilet.

What are some of the issues we have with these products? For help with that, I have engaged our tile and stone expert associate, Donato Pompo.

The leading challenge of ceramic tile and stone flooring is installing it. Despite what some may say, this is not a do-it-yourself product.

Following are some of the most common issues that come up:
1. Lack of thinset mortar contact. ANSI A108.5 says for residential interior dry floors you need to have at least 80% continuous contact between the back of the tile and the substrate with full support along corners and edges of the tile. The 20% of voids has to be dispersed, and there should not be any voids more than two square inches (size of golf ball). For interior wet areas or exterior areas or commercial flooring, you should have at least 95% full contact with full support along corners and edges of the tile with no voids larger than two square inches.

• Often, we find “spot bonding” where the installers just put dabs of thinset down, leaving substantial voids.

• Or we may find that installers will trowel the back of the tile in one direction and then trowel perpendicular to that on the substrate and don’t fully beat in the tile, so continuous contact is only the intersection of the ridges, which is less than 50% contact.

• We also find that some installers don’t beat the tile into the thinset mortar and only gently place the tile because they are trying to avoid tile lippage. You need to beat the tile in to get full coverage and to get a good bond.

2. Lack of slope and drainage. Slope is supposed to be ¼-inch per foot toward the drain on the surface of the tile for interior wet areas and exterior applications but, more importantly, on the surface of the waterproof membrane. If water is trapped under the tile, it can lead to staining problems, spalling damages and create a musty smell. This is a condition that often produces excessive efflorescence staining.

3. Two-part drains have weep holes. Industry standards say to use a weep hole protector or put pea gravel or tile chips around the weep holes so the mortar doesn’t plug them up.

4. Tile lippage is where one side of two adjacent tile edges are higher or lower than the other. Installations normally can’t have more lippage than 1/32” to 1/16” approximately.

5. Most installers learn on the job and have had no formal training, and thus, they are not aware of the industry standards. That is why the University of Ceramic Tile and Stone (UofCTS) has a five-hour online course to teach installers the industry standards, methods and practices that gives the installer the acronym designation of an ITS (Installer Thin-set Standards).

The substrate and tile also have to be level, not varying out of plane more than 1/4” in 10’ for tiles that are less than 15” on any side or within 1/8” in 10’ within the plane to avoid lippage of the floor tiles. The spacing between the tiles should be uniform and even.

Voids beneath the tile as a result of uneven mortar contact can create hollow sounds or can result in tile cracking due to the lack of support.

Installing tile over a wood substrate in a house that will not support the tile or stone can create cracks in the tile due to flexing of the wood. Ceramic tile does not flex or bend unless it is gauged porcelain, which is as thin as 1/8”. If what it’s installed over does deflect, then the tile and the whole installation will be compromised. The standard for tile is the substrate cannot deflect more than L/360 (L = the length of the span being measured).

One of the biggest problems facing tile and stone flooring is the lack of highly skilled installers. If there is an installation crisis for flooring installers in general, there’s a bigger one for tile and stone. These people are craftsmen, many of whom have generational education handed down over the years. Even with industry efforts to make installation easier, there are some things that just can’t be mitigated by technology.

The increasing popularity of large-format tile has created more challenges in installation of these materials, not only for installation skills but also in special tools for the installation. This isn’t a segment for the timid or unskilled.

All tile installers should take the UofCTS installer standards online course to learn the industry standards, methods and practices for all types of tile and stone, including gauged porcelain tile panels, and become Tile Installer Thin-set Standards verified.

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