Are wall and floor tile the same thing? While there is some overlap, differences make one tile better for walls and another tile better for floors.
What's the official definition for "wall tile" or "floor tile"?
Tile manufacturers often categorize tiles as wall and/or floor tiles on their websites. For example, Ann Sacks lists its Athens Gray Field as being right for both wall and floor. Yet its Chrysalis Mosaic is only for wall installations. Unfortunately, some tile companies do not designate their tiles by surface and this gets confusing.
COF ratings are one thing that "define" which tile goes on wall or floor.
Every ceramic or porcelain tile has a certain COF rating. Floor tiles must have a minimum level of friction to make it safe to walk on. This is called Coefficient of Friction or COF, with higher numbers representing more friction. Wall tiles can be as slick as glass (often it literally is glass) because friction doesn't matter. As long as the tile has a COF of 0.50 or greater, the tile can be used on interior floors. Exterior paver tile goes even higher, up to COF 0.60.
PEI ratings are the second factor the define hardness and durability.
The Porcelain Enamel Institute (PEI) issues five classes of PEI ratings that tile companies can use if they wish. Ratings range from Class 1 (No foot traffic, walls only) to Class 5 (Heavy-duty foot traffic, as found in commercial settings). PEI ratings are usually buried within each tile's specifications and are the only true determiner of where a tile can be used.
Rule of thumb: never use wall tile for floors.
In a nutshell, tile that has been rated as right for floors can always be used on walls. But the opposite--using wall tile on floors--would not work. When we say that floor tile can be used on walls, this is only from a functional standpoint. Reasons listed below clarify why you don't want to do this even though technically you can do this.
Wall tile is often softer and less durable than floor tile.
Nobody expects to walk on the wall. Because wall tile usually does not stand up to the abuse of floor tile, it tends to be softer or more prone to breaking. The best example of this is glass tile, which is very brittle and will not last long as a floor material before breaking. But glass' fragile nature doesn't matter on walls, where abuse is not as likely.
Designers recommend smaller tile for walls.
Yes, small tiles are often used on floors. A classic example are 1" hexagonal mosaics that often are installed on bathroom floors. Floor tile can range up to 12" square to 18" or even more. Because of its visible nature and the difficulty of installing wall tile on a vertical surface, wall tile tends to be around 4" x 4" or smaller. As an extreme example, try to imagine 18" square floor tile used on walls: it would look garish and overpowering.
Vitreous surfaces are needed for walls that experience lots of water.
Tile, when installed on walls, is most often installed on shower and bathtub walls. With this high concentration of water, the hard, glazed surface (vitreous) of wall tile is most favorable. By contrast, an absorbent tile such as terracotta or quarry tile can be used on the horizontal floor surface, but would never be used as a wall tile.
Specialty wall tile pieces are more often found on walls, too.
Wall tile lends itself to extra embellishments that are found less often in the floor tile. Bands, borders, and listellos are often found in wall tile installations to improve the look and reduce the visual monotony of these installations.
Exotic materials? Wall tile has it covered.
Unusual and exotic tile materials are more often installed on walls than on floors. We have already mentioned glass as a great wall tile, but also consider leather, tin, stainless steel, and honed natural stone.