Installation of Tile, Mosaic, Glass and Stone
This domain tests the actual setting of ceramic, porcelain, mosaic, glass and stone. The exam expects correct adhesive selection, trowel technique, coverage, open time, support and protection for each material, plus recognition of when a substrate or product is unsuitable.
Core rules
- Select thin-set or adhesive by service condition: dry interior, wet area, exterior, heavy tile, glass or stone. Do not use mastic in showers, exteriors or over membranes that prohibit it.
- Match notch size to tile size and substrate; back-butter large-format tile and stone. Coverage should be at least 80% in dry interior and 95% in wet or exterior areas, unless the standard requires more.
- Respect pot life and open time; do not add water to reactivate cured thin-set.
- Use white thin-set for translucent glass and light stone where colour can show through; follow mosaic manufacturer instructions.
- Support large wall tile with spacers, ledgers or clips; use leveling systems to control lippage without hiding substrate defects.
- Seal stone only as recommended; some stone must breathe or be protected before grouting.
Worked example
A 600 mm × 1200 mm porcelain tile is set over cement backer board on a shower wall. The installer uses a 12 mm × 12 mm square-notch trowel and back-butters each tile. After setting one tile, it is pulled and shows about 75% coverage. The requirement is 95% in a wet area, so the coverage is insufficient. The fix is to flatten the back of the tile with a thin burn coat, use a larger notch or adjust mortar consistency, then recheck coverage. The reasoning: large tile does not conform to a notched bed, and voids in a wet area can collect water and lead to failure.
Traps
Spot-bonding; using too small a notch; skipping back-buttering; setting into skinned-over thin-set; using mastic over waterproofing; ignoring glass translucency; letting leveling clips remain too long; not protecting stone from staining.
Key points
- Match adhesive and notch size to tile type and service condition.
- Back-butter large-format tile and stone.
- Check coverage: 80% dry interior, 95% wet or exterior.
- Respect open time and pot life.
- Use white thin-set for glass and light stone as specified.