When the tile is formed, it creates a void on the back of the tile. By applying a backer inside this void, the tile gains added rigidity and provides a suitable surface to bond to the substrate. The hardboard is the standard backer and works great in most situations. It is not affected by occasional splashings, like behind a sink. We use a 3/16" thick hardboard which stays mostly hidden by the the stainless steel tile's fully-formed factory edge. It has the lowest profile, as it makes a tile that is about ¼&#; thick. It installs easily using a construction adhesive similar to Liquid Nails.
If you are going to use the tile in an area that gets soaked frequently, like in a shower or outside, you will need to use the Fiberock backer. It works great in areas that see a lot of moisture. Because it is a little thicker and makes a tile that is about 3/8&#; thick, it is sometimes chosen when mixing stainless tiles with other types of tile, such as stone, ceramic or glass, to better match their thickness. However, because Fiberock is thicker, it does protrude from the back side of the tile and is NOT hidden by the stainless steel tile's factory edge. It is typically installed with Thinset, like regular tile.
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To summarize, the hardboard backer is 3/16" thick, makes a 1/4" thick tile, and stays mostly hidden behind the tile's fully-formed factory edge. It's our most popular backer and is used in most situations. The Fiberock backer is 1/4" thick, makes a 3/8" thick tile, and because it's thicker, it does protrude from the backside of the tile and is NOT hidden by the stainless steel tile's fully-formed factory edge.
More information on our backers is available here: Tile Backing Options
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