Tile Installation Methods and Materials
Tile Installation Methods and Materials
This domain tests mortar selection, transfer, and method: thin-set vs. mastic, notch size, coverage, membranes, and movement accommodation. Questions frequently ask which product or trowel is correct for a given tile and exposure.
Core rules
- Thin-set mortar is cementitious and suitable for wet areas; organic mastic is for dry interior walls and certain small tile, not shower floors, exteriors, or continuously wet service.
- ANSI A118.1 is unmodified thin-set; A118.4 is modified. Use the manufacturer's specified mortar for the tile type, substrate, and exposure; large and heavy tile often need a medium-bed or large-and-heavy-tile mortar.
- Key the mortar into the substrate with the flat side of the trowel, then comb with the notch. Back-butter large tile or where the substrate is uneven. Coverage should be at least 80% in dry interior areas and 95% in wet, exterior, or heavy-duty areas, with full support at corners and edges.
- Use a notched trowel that leaves ridges high enough to collapse under the tile; check by lifting a freshly set tile. Mix to the stated water ratio and respect pot life and open time.
- Install movement joints at perimeters, transitions, and large field areas; do not grout them-use sealant.
Worked example
A 12x24 porcelain tile is set over a flat concrete slab with a 1/2x1/2-in. square-notch trowel. After pressing a tile into the mortar, lift it: mortar covers only 70% of the back. The fix is to key in the mortar, back-butter the tile, and use a larger or different notch as needed, then recheck coverage before proceeding.
Traps
Dot-setting tile to save mortar; using mastic in a shower; adding water after mixing to extend pot life; and judging coverage by looking at the surface instead of lifting a tile.