QUESTION

I am seeking a website or tile install standard for glass tile, specifically, a clause that explains /states there is to be a crack isolation barrier or elastomeric sheathing behind the glass tile, to help prevent or mitigate cracking.

My installer is saying it is not necessary, but I want to verify the national industry standards and make sure it is installed properly.

ANSWER

ANSWER - There are no mandatory requirements to install glass tile over an ANSI A118.12 crack isolation membrane, unless the substrate to which the tile will be adhered to has non-structural cracks.  Tile cannot be installed over cracks as the cracks can then telegraph through the tile.  Crack isolation membranes can only mitigate non-structural cracks, and cannot be used over structural cracks in the substrate.  The TCNA Handbook for Ceramic, Glass, and Stone Tile Installation does offer some recommendations regarding the installation of glass tile over any type of a membrane.

The TCNA Handbook does state that glass tile is generally more vulnerable to crack propagation than ceramic tile.  Where opacity allows the glass tile manufacturer may recommend the use of an ANSI A118.12 crack isolation membrane for large format glass tiles.   It states that bonding translucent glass tiles directly to membranes or other impervious surfaces is not recommended because any moisture trapped between the tile and membrane would be visible.  Select only opaque glass tile if the tile will be bonded to a membrane.

Thus check with the glass tile manufacturer to see if they recommend a crack isolation membrane.  Don't install a crack isolation membrane under translucent glass tiles.  If the glass tile manufacturer doesn't recommend a membrane, if the substrate is structurally sound with no cracks, and if you have properly designed and installed movement joints throughout the tile installation, per TCNA EJ171 requirements, you should not need to bond the glass tile to a crack isolation membrane.