Choosing the Right Tile
Make sense of PEI ratings, glazes and materials with this primer.
Tile terminology can be confusing. PEI ratings, glazes and just telling the difference between porcelain and non-porcelain tiles can leave consumers bleary eyed. To help you navigate these issues and find the right tile for your particular application, the information below includes descriptions of the different types of tiles, from ceramic to marble, as well as details on wear ratings.
Porcelain or Non-Porcelain Ceramic Tiles?
Most types of tiles made from a form of clay or a clay mixture and kiln-fired are considered to be a part of the larger classification of tile called ceramic. These tiles can be split into two groups, porcelain tiles and non-porcelain tiles, and the non-porcelain tiles are commonly referred to as ceramic tiles.
Non-porcelain ceramic tiles are generally made from a red or white clay that's fired in a kiln. They're easier to cut than porcelain and usually carry a PEI (Porcelain Enamel Institute) rating of 0 to 3 (see PEI ratings below). Ceramic tiles are suitable for light to moderate traffic and are more water-absorbent, making them less frost-resistant than porcelain. In addition, they're usually more prone to wear. However, with new technologies, ceramic tile should always be considered by its specifications, as durability and other factors will vary among ceramic tiles. Ceramic tiles generally cost less than porcelain tiles.
Porcelain tile is generally made by pressing porcelain clays, which results in a tile that's dense, impervious, fine grained and smooth, with a sharply formed face. Porcelain tiles usually have a much lower water-absorption rate than ceramic tiles, making them more frost-resistant, although not frost-proof. Glazed porcelain tiles are much harder and have more wear- and damage-resistance than ceramic tiles, making them suitable for any residential and light commercial application. Most porcelain tiles have a PEI rating of 5.
To enhance the stain resistance of a stone tile, many tiles are glazed. This means they're coated with a liquid glass that's baked onto the surface of the clay. In addition to protecting the tile from staining, the glaze also allows an unlimited array of colors and designs to be added to the tile. Porcelain tiles whose color runs all the way through the tile, rather than simply being baked onto the surface, are called full-body tiles. Since their color extends throughout the tile, these tiles don't show wear, making them ideal for commercial applications.
Regardless of which you choose, be sure to seal the tiles periodically to maintain their beauty.
Ceramic Tile Wear Ratings
The current rating system for ceramic tile is the only reliable gauge for consumers to use in determining wear expectations for a particular tile application. The Porcelain Enamel Institute has developed a rating scale that can effectively guide any consumer through the process of choosing the right tile for a particular application. This rating system is recommended by the American Society for Testing and Materials.
- PEI Class 1 Rating (no foot traffic): Recommended for wall use only in residential and commercial applications
- PEI Class 2 Rating (light traffic): Recommended for both wall use and bathroom-floor applications
- PEI Class 3 Rating (light to moderate traffic): Recommended for countertops, walls, and floors where normal foot traffic is expected
- PEI Class 4 Rating (moderate to heavy traffic): Recommended for all residential applications as well as medium commercial and light institutional.
- PEI Class 5 Rating (heavy to extra-heavy traffic): Recommended for all residential as well as heavy commercial and institutional applications.
Natural Stone Tiles
In addition to the many choices you have in ceramic tiles, there's a wealth of options among natural stone tiles. There are many subtle and significant differences among the types of stones available, from appearance to water absorption to durability. And no two natural stone tiles are the same each has its own natural beauty. The natural stones most commonly used in tiles are slate, marble, limestone, travertine and granite.
Slate is a fine-grained, metamorphic rock, commonly derived from sedimentary rock shale. It's composed mostly of micas, chlorite and quartz and is best-suited for floors, walkways, roofing, kitchen countertops and wet bars.
It's a dense, tough composite typically available in blacks, grays and greens, although it can also be found in many other colors. Slate shades within the same color family often vary. Veined patterns from overseas are also available. Unless it has been honed smooth, slate's surface can be recognized by its distinct cleft pattern.
Marble is one of the more popular natural stones, formed from fossil sediment deposits that have been pressed by the natural geologic forces of nature for millions of years. Much as diamonds are created from coal, marble was once limestone that underwent a metamorphosis from the intense pressures and high temperatures within the Earth.
The combination of the natural materials in these deposits and natural geologic events produces unique colors and veining of great depth and intensity. Most marble products are softer and have more porosity than granite. Because it's softer, it's most often used in bathroom walls and flooring, as well as for tub decks, fireplace surrounds, furniture, sculptures and courtyards. Marble is not recommended for kitchens unless the stone is honed and sealed.
Limestone is a form of marble that's less dense than marble or travertine (itself a form of limestone). Limestone is a sedimentary rock consisting mostly of calcium carbonate and is formed from the remains of ancient sea life such as oysters and mussels that have been compressed over millions of years.
Limestone is a common stone found in great abundance in many parts of the world, generally in earthy colors such as off-white, grey and beige. Limestone that contains the mineral dolomite is hard enough to be polished to a shine much like marble can be. Its best uses are for structural walls, entry walls, floors, fireplace surrounds, vanities and shower walls. It's generally not recommended for kitchen countertops and wet bars, because fruit juices and alcohol products can stain it and it's prone to scratches.
Travertine is a variety of limestone formed in pools by the precipitation of hot mineral-rich spring water. It's another form of marble that's less dense than a high-grade marble and highly porous. The divots characteristic of travertine were created by carbon dioxide bubbles that became trapped as the stone was being formed.
Travertine can have a honed, unfinished surface, or the holes can be filled and then polished to a high gloss. It's best-used in entry walls, floors, fireplace surrounds, vanities, shower walls, tub decks and mosaics and is not recommended for kitchen or wet-bar countertops, since it can be easily scratched. It can also be easily stained by fruit juices and alcoholic products. Its colors usually range from light beige to brown. Travertine requires a degree of special care, as some cleaning products can be destructive to its surface.
Granite is a dense-grained hard stone. It's actually the second-hardest known substance, behind diamonds. Granite is an igneous rock formed either from the melting of sediments deep within the Earth or through magma (lava) activity. The sediments were held under extreme pressure and temperatures for millions of years and then brought to the surface of the Earth through upheaval of the crust that formed mountains. This process produces granite, a quartz-based product, which combines strength and durability with rich patterns and veining.
Minerals within granite typically appear as small flecks throughout the stone, often creating a salt-and-pepper look. Other types of granite have veining similar to marble. Once polished, natural granite will maintain its high-gloss finish virtually forever. It also cleans in seconds. Because of its durability, it can be used for kitchen countertops, wet bars, entry walls, floors, fireplaces and bathroom vanities. Flamed or honed granite can be used almost anywhere.
Buyers should note that no two natural stone tiles will be the same each has its own natural beauty. Homeowners must be sure to seal the stone periodically, however, in order to maintain that beauty.
Interior designer Angela Miller has trained in hard and soft flooring, ergonomics, and commercial furniture and textiles. Reprinted with permission from the National Kitchen & Bath Association