Installing tiles that have different thickness
The challenge: to selectively build the substrate under glass tiles in a desirable way.
Ten or fifteen years ago, when nearly all commercial glass tiles were 1/8" thick, installers had a recurring problem of having to fit thin glass tiles into a thicker ceramic tile installation. Today, many glass tiles are produced in thicknesses matching ceramic tile, but there will always be cases when the problem of various tile thickness needs to be addressed.
The most common mistake it to simply build up a thicker layer of thinset adhesive under the tile. Thinset, as the name implies, has been designed to be applied in a thin layer. If applied in a thick layer it will dry on the outside only, leaving the inside soft and wet for a long time. If glass or glass tile is stuck to the outside of this slowly shrinking blob, the tile can crack during the long drying process.
A more effective solution is to use a dry pack mixture - the same material used to build the bottom of a shower pan. Dry pack mixture is designed to be more stable and will not shrink and crack (or at least, it will shrink much less than a thick layer of thinset adhesive). To do this properly you would have to partially fill the space for the glass tile with dry pack, let that dry and finally install the glass tile with a good flexible, rapid setting, white thinset that has been tested with glass tiles (such as Mapei's Granirapid).
If this sounds complicated, there is a simpler system. Schluter makes a waterproof membrane called Ditra that can be used to support a tile's apparent height. Ditra only comes in 1/8" thickness , so it will not work to exactly compensate for every height differential.
Note that one of our sponsoring companies, Interstyle Ceramic & Glass, has also developed cheap plastic extrusion of various thicknesses which, like Ditra, provides thickness as well as grip for the thinset to adhere to. Whichever solution you choose, install by attaching the matting to the substrate, and attaching the glass tile on top.
Both of these "sub-mat" approaches give a single, simple, effective solution to uneven tile thicknesses that is inexpensive and quick to apply.
Information on these pages is offered as a background and guideline. No warranty is implied. Always check with your tile manufacturer for an installation method that they will stand behind.
