Mosaic Ceramic Tiles
Mosaic ceramic tiles, or tiles that measure two inches in size or smaller, require a thin, tight groove for installation. Choose a V-notched trowel for any mosaic installation. Tiles measuring one inch or less in size should use a 3/16-by-5/32-inch trowel. Tiles measuring two inches should use a 1/4-by-3/16-inch trowel, although any V notch can handle mosaic ceramic tiles in a pinch.
Wall Tile and Small Floor Tile
Most ceramic wall tiles measure four inches up to six inches square, and 3-by-6 or 4-by-8 inches in rectangular sizes. Square notched trowels work the best for wall tiles in this size range, and for smaller floor tiles measuring six inches or smaller in size. Choose a square notched trowel that measures 1/4-by-1/4 inches for best results.
Larger Wall Tiles and Small Floor Tiles
Wall tiles measuring six or eight inches square or extended subway tile sizes such as 4-by-12 inches, as well as six- and eight-inch floor tiles can use a square or U notched trowel. Look for trowels that measure 1/4-by-3/8 inches in size in either square or U notch. For tiles that straddle two trowel sizes, use the larger trowel size for tiles that are 3/8 inch or thicker, or that are handmade and have irregular backs.
Large Ceramic Floor Tiles
Ceramic floor tiles come in sizes up to 24 inches square. Use a square notched trowel for any tiles measuring at least 12 inches square and 3/8-inch thick. A 1/2-by-1/2-inch trowel is best for larger floor tiles. For 18- and 24- inch tiles that are 1/2-inch thick, use a U notched trowel that measures 3/4-by-5/8 inches for best results. A 1/2-inch square notched trowel will work for larger sizes, but back buttering, or applying of additional mortar to the backs of the tiles may be required for a good bond.