2024-25_NTCA_Reference_Manual_dig_dwnld

1/2" x 1/2" x 1/2" Notch Trowel

Precautionary Statement

The 1/2" x 1/2" x 1/2" trowel was introduced to the market with the intention of providing additional mortar to facilitate the installation of larger tile and as such has become an extremely popular trowel. The only drawback is that this additional mortar does not yield better coverage and/or transfer using this trowel. While it is true that larger tiles require more mortar than a smaller tile, the trowel design rather than the amount of mortar placed is the secret to successful tile installations. To obtain adequate mortar coverage, transfer, and support for large format tiles, having a facial dimension greater than 23", the appropriate trowel design is critical. The use of a Large and Heavy Tile (LHT) mortar aids in setting heavy tile, generally tile that is five pounds per square foot or heavier, and tile of ungauged thickness. However, LHT mortars are not intended for truing or leveling substrates or the work of others. All substrate tolerances for the installation of tile with one side 15" or longer must be within industry flatness standards of 1/8" in 10' using trowel-applied patch or flowable hydraulic cement underlayment (FHCU) formerly self-leveling underlayment (SLU) before the installation begins. The issue with the 1/2" x 1/2" notch trowel is the distance between the notches. The wide space between the notches makes it difficult, if not impossible, to fully collapse the mortar ridges into the valleys. This is especially true when the specified grout joint is 1/16" to 1/8" which limits the ability to move the tile in the back-and-forth motion as seen in the NTCA Trowel and Error video. When using a 1/2" x 1/2" notch trowel, the tile must now be moved at least 1/2" in a back-and-forth motion to collapse the troweled mortar ridges. This is impossible to achieve due to the wide valleys between the ridges, the thin grout joint widths and adjacent tiles along the installation pattern.

MOVE 1/2" TO THE LEFT – MOVE 1/2" TO THE RIGHT

1/2"

1/2"

1/2"

1/2"

1/2"

1"

Installing large tile with a 33% offset and a 1/8" grout joint using a 1/2" x 1/2" trowel is a recipe for failure. It is impossible to move the tile far enough to collapse the 1/2" ridge into the adjacent 1/2" valley.

1/8" GROUT JOINT

1/2"

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NTCA Reference Manual | 2024 / 2025

Chapter 8 | Thin-Bed Method Installations