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Bonding Large-Size Tile For Coverage, Support and Reduced Lippage

The procedure is: 1. Key mortar into

4. Pressing firmly move back in the opposite

suitable substrate to receive ceramic tile or stone with the flat side of the trowel.

direction 1/8 in. to 1/4 in. (3 mm to 6 mm) to flatten ridg es into the valleys, removing air from between the mortar and tiles.

2. Comb – in one

5. This method can produce specified coverage with

direction – with notched side of properly selected trowel.

the corners and edges fully sup

ported, without flat back-troweling or beat-in.

6. Periodically remove and check a tile to assure proper cov erage is being attained.

3. Firmly press tiles into mortar and

move perpendicular across the ridges approximately 1/8” in. to 1/4 in. (3 mm to 6 mm).

(photos not to scale)

Proper Troweling Method can be found online at http://bit.ly/NTCATrowelandError

NOTE: This procedure is not intended to overcome improper trowel selection or substrate preparation required by ANSI Specifications. Refer to the TCNA Handbook’s “Substrate Requirements” section for more information on Substrate Tolerances, Mortar Coverage, Flatness and Lippage information. Tiles 8 in. (203 mm) square or larger present special challenges and require new procedures to produce professional and aesthetically acceptable installations. Rectangular and square tiles up to 16 in. (406 mm) and 24 in. (610 mm) have become quite common. Even tiles up to 48 in. (1219 mm) are available to the tile trade, not to mention larger marble and stone tiles, and GPTP panels which have their own installation standards (see ANSI A108.19 and A108.20).

Emphasis must be placed on the necessity of other trades providing a flat and even surface for the professional installation of these large size products.

New installation techniques are required to aid in reducing installation time and ensure specified coverage of dry-set mortar over the entire bonding surface of the larger tiles, including full support of edges and corners.

The biggest changes in the use of dry-set mortars for installing larger tiles are the methods in which mortar is troweled on and bedding of the tiles into the mortar relative to the direction of the trowel ridges.

Traditionally, dry set mortars have been applied with the notched side of the trowel in a swirling motion of the wrist and arm. This might be marginally acceptable for smaller tiles, however, where the swirls come together or cross, air is trapped and larger masses of mortar are formed than is present in a straight trowel ridge, making it difficult if not impossible to disperse the mortar uniformly to produce even surfaces with larger tiles.

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NTCA Reference Manual | 2024 / 2025

Chapter 8 | Thin-Bed Method Installations