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Flat Back-troweling & Notched Back-troweling

SUMMARY Flat back-troweling and notched back-troweling are not re quired for most installations, refer to ANSI or TCNA Handbook methods as to when either one of these techniques is recom mended or required. Certain references in industry specifications and manufac turers’ literature may leave the specifier and installer unsure about the necessity or requirement for flat back-troweling and notched back-troweling. If the thin bond coat on the back of the tile that is considered flat back-troweling is not embedded thoroughly enough to contact and collapse the notched ridges of a properly-prepared installation surface, it serves no purpose except to increase the cost of the installation through extra ma terial and labor costs. As with all installations, the bond coat coverage required de pends on the type of installation. Per ANSI A108.5 interior or non-wet area installations require 80% coverage, while exteri

or, wet area and stone installations require 95% coverage. Flat back-troweling a tile cannot take the place of the coverage re quirement. It may look like you have 100% coverage when you flat back-trowel a tile, however, coverage also requires for the tile to be fully supported as specified under A108.5. Notched back-troweling can help with the coverage requirement and support of a tile, but once again a properly-prepared installation surface with the proper sized notch trowel will ensure the cov erage and full support as required by ANSI and the TCNA Hand book . It is the position of the NTCA Technical Committee that install ing tile using the one directional troweling method and col lapsing the ridges through a sliding motion perpendicular to the troweled ridges is the best method for properly installing tile. There are specific uses for flat back-troweling and notched back-troweling. If these specific uses are not done properly, there is little to no benefit to the tile installation, only causing increases in time and cost.

Mark Heinlein, NTCA Technical Director, demonstrating flat back-troweling.

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NTCA Reference Manual | 2024 / 2025

Chapter 8 | Thin-Bed Method Installations