Porcelain tile is made from natural clay that is baked at a very high temperature until most of the moisture is removed. Because of its low moisture level, porcelain tile is a fairly strong and durable product and is often used to finish floors, walls and countertops. In the United States, porcelain tile is graded according to a Porcelain Enamel Institute (PEI). The PEI scale measures the durability of the tile, and helps buyers choose the right tile for their project.
Grade I porcelain tile is the least durable of all porcelain tile products. It is unsuitable for use on floors and countertops, and is designed only for use on walls. Tiles with a Grade I rating are recommended for indoor residential applications only and are traditionally used on bathroom walls or to create a backsplash over a kitchen countertop.
Tiles with a Grade II rating are designed to withstand light traffic only. They may be used to finish kitchen or bathroom floors in residential homes, but should not be used for commercial flooring. In light commercial applications Grade II tiles can be installed on walls or countertops when little or no abuse is expected. Homeowners with pets or children may want to consider a Grade III tile when covering floors.
Grade III porcelain can withstand light to moderate foot traffic and abuse. It can be safely installed on most residential and light commercial floors. Businesses such as beauty salons or small boutiques may choose this product for entrance ways or entire rooms. In residential applications Grade III tile can be used on kitchens, hallways and other areas exposed to frequent traffic. It may also be used for countertops with minimal risk of damage.
Tiles with a Grade IV designation are intended for commercial use, though some homeowners may decide to use them as well. These tiles can be used on almost any floor regardless of traffic levels, though they are not designed for heavy industrial use. Because they are designed for strength and durability, colors and finishes may be limited with Grade IV tiles.
A Grade V tile is designed for use in very high traffic and high abuse scenarios. This may include schools, shopping centers and grocery stores. This is also found in industrial buildings, where it can withstand abuse from machines and equipment as well as exposure to chemicals. Grade V tiles are available in a limited selection of finishes, and are usually chosen based on strength rather than appearance.