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Understanding Tile and PEI Ratings

November 21st, 2014 No comments

In general, for most people’s purposes, tile can be divided into a couple of categories, such as tiles suitable for walls (baths, showers, back-splashes, fireplaces) and tiles suitable for floors, (shower floors, foyer entries, kitchen floors, sun-rooms, hearths, exterior porches and walkways, etc.).
The composition of the clay body,  how densely the clay body was pressed when made,  and whether it is glazed, unglazed, or honed to a matte or polished finish, are all things which determine where it can be best used.
The main types of tile are ceramic, porcelain, marble, stone, and granite. All have different characteristics and can be used to good effect almost anywhere if set properly.  Even an inexpensive tile can give good service, “ if set properly”.

We have tiled outside roof-decks, stairs both interior and exterior, garages, cabanas, pools, architectural features, mall store façades, and the ordinary tub surround.  Basically, one of the main things about where and how a tile can be used is how much water the clay body of the tile will absorb when exposed to water.  The dividing line between ceramics and porcelain tiles is a little fuzzy depending on the amount of glass in the clay body and it’s density.

“I have see tiles classified as ceramic one year go to being classified as porcelains the next year due to the manufacturer changing it’s formulation.” from Bart Raguso

Ceramics

If you dip a tile into water and you are looking at the back of the tile, and the water quickly disappears and the tile looks dry, you are holding a ceramic tile in your hand.  This type of tile bonds readily to mortar because of this fact, but cannot be used outside where they could be frozen and “spall”, or split apart.  But they are fine for interior applications or in warmer climates.  Most ceramics used to be thicker to increase their strength, but now are thinner. This may have something to do with better manufacturing techniques and the ability to ship more product. I do not know, but if the clay body is red or white, it is usually a ceramic. Ceramic tile is glazed and if the glaze is chipped, you will see the clay underneath.

Porcelains

Porcelains, pavers, and quarry tile have a higher amount of glass in the clay body and are pressed to a higher density enabling them to be used outside and almost anywhere else.  They usually have the same color all the way through ( through-body ) and can be honed or polished to a high gloss like marble or stone. They are ‘harder’ but more brittle and they can still chip if sharply struck.  Mother Nature does not give you something on one side without taking something away on the other.  Also porcelains can be more difficult to bond to your substrate if the right mortar and technique are not used.

Stone and marble

Stone and marble are the classics and have been used for thousands of years by humans, but they demand a little more care and maintenance. If they are in your budget, they are preferred by many for their beauty and timelessness. They are like a little slice of time captured somewhat like a photo and infinitely variable, like the world itself.

Granite

Finally, we come to granite. Granite is almost as hard as diamond as measured by “Mohs’ scale of hardness, the ability of one material to scratch another. Granite is almost 9 and diamond is 10, but the scale is a little like decibels, with variable levels, not an absolutely even scale. There is a great Wikipedia article- https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness if you are so inclined. Anyhow it is hard and is often the choice for a fairly impervious surface, if you like the colors. I should mention some granites are only cousins to the granite family and do also require sealing, like other stone.

To sum up, most all tiles are good, if set right.  What personally resonates with you should be your guide.

The following table sums up the PEI ratings:

P.E.I Wear Ratings

    • from the Porcelain Enamel Institute

      Group I: Tiles that are suitable for residential bathrooms with light foot traffic . Generally wall tile products fall into this group. Some wall tiles can be used on the floor. Consult the manufacturer of the tile for their recommended areas of application.

      Group II: Tiles that can be used in residential areas, but not areas with high foot traffic, such as in kitchens, foyers, laundry rooms, etc.

      Group III: Tiles that are recommended for all residential installations with normal foot traffic.

      Group IV: Tiles that are suited for light to medium commercial applications, such as offices, sales rooms.

      Group V: Tiles used in heavy commercial traffic areas and are suited for exterior areas, shopping centers, airports, hotel lobbies, public walkways.