Sunday, January 9, 2011

Review of Ceramic Tile Types and Facts-ADA Flooring/Tiles.

There are two major types of tile that can be used for wall tile, mosaic tiles and floor tile.
·       Quarry tile: that is tile that is made by extrusion from natural clay or shale.
·       Tile that is made by the pressed dust method.
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.)
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·       Wall tile has from 7-20% water absorption (that's right, it's a lot). That's why you shouldn't use wall tile outside where there can be freezing temperatures. The water goes into the body when it rains, snows, from pools and fountains, and even condensation, and then it expands when it freezes and the tile cracks. So don't put this tile outside in most places in the U.S. Even Florida and California have some freezing days in most parts of the state. The same holds for "Saltillo" tile that rough looking hand pressed Mexican tiles. These can have water absorption up to 30%.
Wall tile is made for a purpose, sticking on a wall (although it can be used on countertops and sometimes on floors. The relatively soft body of wall tile makes it easy to cut to fit (including round holes for plumbing fixtures) and helps the tile to stick to the wall without sliding.

Quarry tile has water absorption less than 5%.
·       When it is extruded, a dense surface forms that reduces the staining and surface porosity  of the unglazed tile (remember all tile can be glazed).
·       Can be made very thick and therefore strong.
·       Quarry tile a good candidate for warehouses, fast food places with high traffic, commercial kitchens, dairies, meatpacking plants and other areas where strength and ability to clean are paramount.
·       If it is used unglazed (which it generally is) it doesn't have a thin surface to wear out and will last a very long time.

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. 

·       It is harder to get adhesive to stick to the tile. Wall tile with its high water absorption will "grab" into the adhesive fast and stick well to a vertical surface. You can use porcelain tile on a vertical surface but it needs to be physically supported while the adhesive sets, for example with plastic spacers or boat rope. Use the best adhesive available for these tiles, latex modified thinset or epoxy.

·       Porcelain tile is harder to cut. Your grandfather's snap cutter or carbide blade will be challenged when cutting this product. You need a diamond wet-saw. While on this subject and in case you feel like going home to set tile tonight, do not under any circumstance use a dry blade in a power saw to cut tile or any other product that contains silica. The watchdogs at OSHA are developing standards for exposure to silica dust as I speak to you. It's not as good idea to breathe this stuff even if the medical science is still being evaluated.

·       Even with low water absorption, because the surface may be unglazed, there is a surface micro-porosity (real little holes on the surface) that can allow staining. Not good if you drop ink on your floor. The manufacturers are solving this by adding a clear glaze to the surface of the "unglazed" tile.

·       Color ranges and finishes of unglazed porcelain pavers has been limited and considered more of an institutional look. This too is being addressed and many new styles and colors are coming into the market.

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?
·       Small porcelain tiles that can be either glazed or unglazed, and I won't say that again, I promise.
·       Less than six square inches and generally are sheet-mounted at the factory to save time in installation. Who wants to put little one by ones in a 40,000 square foot shopping mall piece by piece?
·       Strong and have low water absorption and have some real advantages.

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.

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