How to Determine the Quality of Ceramic Floor Tiles

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Ceramic tiles are rated via the American Society for Testing and Materials for their abilities to withstand normal use circumstances. These factors determine the safety of the tile and its recommended usage. In addition to these tests, tiles also are graded for overall quality. When selecting ceramic tiles, it's important to compare all ratings to get the best tile for your application.

Tile Grading

Tiles are graded using a numerical numbering system based on their thickness and quality. A rating of 1 is the highest quality and thickest tile available, 3/4-inch thick, and you can use them anywhere. Grade 2 reflects that some imperfections exist but the tile still is usable on walls or floors. These tiles are approximately 1/2-inch thick. Grade 3 tiles are the thinnest, 1/4-inch thick, and are appropriate for use only on walls. Grades 1 through 3 sometimes are referred to as standard, secondary or cull grade, respectively.

Wear Rating and Scratch Resistance

The Porcelain Enamel Institute rates tiles on their ability to resist abrasions caused by everyday wear and tear. The higher the roman numeral beside "PEI" in the printed rating, the better the resistance. Tiles rated I or II are not suited for installation on a floor. Floor tiles must be rated at III or higher for residential use; the highest rating, IV, is recommended for high-traffic commercial floors. The PEI rating applies only to glazed tiles.

Glazed and unglazed tiles are rated for scratch resistance and hardness via the Mohs scratch test. The tiles are rated from a soft 1, or Talc, to 10, or Diamond, the hardest tile available. A random selection of tiles is scratched with special testing tools, each with a different mineral hardness, until the surface shows the scratch mark made. A rating of 5 or higher is recommended for home flooring and 7 or higher for commercial floors.

Water Absorption and Frost

A tile's water absorption rating helps you determine if the tile is suitable for installation in your room. The rating is calculated based on how much water the tile absorbs in relation to its weight. For example, tiles rated as nonvitreous will not survive a high-moisture environment such as a shower because they absorb more than 7 percent of their weight. For wet areas, including exterior patios, the tiles must be vitreous or impervious. This test is completed by exposing the tile to dyed, standing water for 16 hours and then checking for penetration.

In combination with the water absorption rating, tiles are rated for frost resistance. Vitreous and impervious tiles are frost resistant because they don't absorb enough water to freeze and crack the tile. Unlike water absorption, frost resistance is not rated as a number. If the frost-resistant symbol is present, the tile is not subject to freeze/thaw damages. This icon is not applicable if you intend to use the tiles indoors.

Coefficient of Friction

The C.O.F. rating denotes the force required for an object to move across the surface of the tile divided by the tile's weight. The primary concern for this rating is whether a person walking on the tile risks slipping due to lack of friction. The rating is preferred to be above .50 foot pounds for home installations and must be above .60 for commercial buildings under the Americans with Disabilities Act. The values are indicated first in foot pounds, followed by SI Units in parenthesis on the tile information sheet.

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