Why Glass Tile Is Different
Glass tile is translucent or transparent. Unlike ceramic or porcelain tile, light passes through it — which means the material behind it (the thinset) is visible through the face. Any trowel mark, color variation in the mortar, or void in coverage shows through the tile and looks terrible. Glass tile is also non-porous (it doesn't absorb thinset), which means bonding requires the right mortar chemistry. And glass expands and contracts more than ceramic with temperature changes, so it's more prone to cracking if it can't move.
The Standards: ANSI A108.15 and A118.13
ANSI A108.15 is the installation standard specifically for glass tile. ANSI A118.13 covers the mortar required. Key requirements from these standards:
- •Use a glass tile-rated mortar (A118.13): Standard thinset is not approved for glass tile. You need a mortar specifically formulated and tested for glass tile — look for "non-sag" wall mortar with extended open time, labeled for glass tile use.
- •Use white mortar: Any gray thinset will show through clear or lightly colored glass tile. Always use white mortar for glass tile installations. Even when using colored glass, white mortar produces the truest color rendition.
- •Full coverage is critical: ANSI A108.15 requires 95% mortar coverage on glass tile — same as wet areas — because voids show through the glass as dark spots and because glass tile is thin and can crack over voids under thermal stress.
- •Expansion joints: Required per TCNA EJ171 due to glass tile's higher thermal expansion. At minimum, install expansion joints at all perimeter edges and at material transitions.
Substrate Requirements
Glass tile will not hide substrate imperfections — it will amplify them. The substrate must be:
- •Flat to 1/8 inch over 10 feet: Any high spot or depression will create a visual shadow through the glass. This is significantly flatter than typical ceramic tile requirements.
- •Rigid — no flex: Glass tile cracks under deflection. On walls, this means well-fastened cement board or tile backer with proper framing. On floors, glass tile is generally not recommended unless structural deflection is extremely low (L/600 or better).
- •No existing tile with hollow areas: Installing glass tile over existing ceramic tile is risky — any hollow spot in the existing tile amplifies movement.
Grout Selection for Glass Tile
Use unsanded grout for glass tile. Sanded grout contains fine quartz particles that can scratch glass tile faces as you work the grout into joints and wipe it clean. Most glass tile is installed with tight joints (1/16 inch) that require unsanded grout anyway.
Epoxy grout is another excellent option for glass tile — it's stain-resistant, highly durable, and will not scratch glass. The trade-off is cost (2–3× cement grout) and working time — epoxy grout sets fast and must be cleaned off glass tile surfaces completely before it hardens.
Installation Technique for Wall Glass Tile
- Apply mortar to the wall with a 3/16-inch V-notch trowel (for mosaic glass) or 1/4×3/8-inch square-notch (for 4×4+ glass tiles). Comb in one direction.
- Collapse the ridges by combing across with a flat edge or back of the trowel — this creates a smooth, consistent bed that produces a more uniform look through the tile.
- Back-butter each tile or each mesh-mounted sheet with a thin skim coat of white mortar. This is critical to achieve 95% coverage.
- Set tiles with a slight sliding motion to embed them fully. Use a grout float or rubber mallet with a beating block to press evenly without cracking.
- Pull a tile immediately after setting to check coverage. Adjust technique until you consistently achieve 95%+ contact.
- Allow mortar to cure fully (24–48 hours) before grouting.
Best Applications for Glass Tile
- •Kitchen backsplash: The most popular and practical application. Subway-format glass tile or mosaic glass for a backsplash is relatively low-risk (no foot traffic, no heavy structural demands) and creates beautiful light reflection.
- •Shower accent wall: One wall of glass tile in a shower with three ceramic walls is a classic look. The glass wall catches light from windows or fixtures and makes the shower feel larger and brighter.
- •Pool interior: Vitreous glass tile is designed for pool interiors and is the standard for high-end pool finishes. This is a specialized installation requiring pool-rated setting materials.
- •Not recommended for floors: Glass tile on floors is a specialty application requiring very low deflection substrates. Most residential floor applications are better served with porcelain or ceramic.
Related Reading
Planning a Glass Tile Project?
Glass tile requires experienced hands and the right materials. Tilers4you has installed glass tile backsplashes and shower features throughout Aurora and Denver — contact us to discuss your project.