There are two major types of tile that can be used for wall tile, mosaic tiles and floor tile.
Glaze is a ceramic surfacing material that is used to provide a certain appearance, any ceramic tile type may be glazed or unglazed. This includes porcelain tiles.
The water absorption determines the classification of tile. How can a tile absorb water, you ask? It is a dense body of minerals that is heated to a high temperature and is not like a sponge. The answer is that it can. One dries a tile then weighs it, soaks it in water and then measures it again. The weight change represents the % of water absorbed. (Weight after soaking minus weight when dry divided by weight when dry is % water absorption.)
Quarry tile has water absorption less than 5%.
What are porcelain tiles? Tiles with a water absorption of less than 0.5%. But wait a minute; if these porcelain tiles are so perfect why not use them everywhere? Well, there are some consequences of making a tile with near zero water absorption.
Glazed pavers. These can have low water absorption, as low as zero, but generally the manufacturer makes them with 2-3% absorption in order to improve the bonding, and ease the cutting operation while still providing adequate break-strength and frost resistance. Yes, these lower water absorption tiles from zero to 5% can be used outside even where it freezes.
Mosaic tiles. What are they?
Because they are small (about 2-1/4″ by 2-1/4″ maximum) they will follow a contour such as in shower floor. They allow for many drainage channels in wet areas to improve the slip-resistance (more on this later) and they provide for many geometric designs. They recently have become quite popular as accents to larger tiles. If they are left unglazed, they will last for a very long time.
Is it a good idea to use tiles that can absorb 7-20% water (usually they absorb about 12-14%) in wet areas?
- The surface glaze is impenetrable to water and acts as a barrier when this tile is used in bathtubs, showers, pools, and elsewhere where there is water.
- Water will penetrate the grout joints no matter how careful the installer is. This means that some method of protecting the underlying backing material needs to be used, in wet areas, such as a liquid or solid water-proof membranes or waterproof materials (i.e. cementitious backerboard).
And now to the finishing touch: glaze. Glazes are a thin finish that can and will eventually wear off of the tile. Selection of the area of use for different glaze ratings is important. Currently the industry is using the following glaze wear rating system (as is ISO, the International Standards Organization and most of the world):
0 – Decorative tile only (look but don’t scrub)
1 – Non-traffic area tile (put it on the wall)
2 – Light traffic (like in the bathroom with slippers and bare feet)
3 – Residential inner rooms (kitchens, sunrooms, etc)
4 – Light commercial (office buildings, showrooms, entry-ways)
5 – High traffic (shopping malls, fast food, etc.)
Finally, a lesson on coefficient of friction (COF) and then I’ll slip out of here. There are no national standards or requirements for coefficient of friction. There are some local municipalities that have building codes, however. The American’s with Disabilities Act (ADA) recommends a COF of 0.6 or greater on flat surfaces and for people with disabilities and 0.8 on ramps and inclines, but there are no laws, standards or whatever specifying the COF.