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Flat Back-troweling & Notched Back-troweling

stalled. ANSI A108.19.15.0 contains the required mor tar coverage requirements specific to GPTP.

There are a few instances in installation procedures, such as installing tile on a ceiling, installing irregu lar or cleft stone tile or installing handmade tiles that are naturally warped, where it may be advantageous to key the mortar into the substrate and use notch back-troweling to apply mortar to the back of the tile before placing the tile on the substrate and embed ding the tile. And if for any reason, like in the case of GPTP, it is necessary to notch-back trowel both tile and substrate, the notches must be in one direction, aligned (parallel) with the substrate notches creating a zipper effect and fully collapsed to achieve the nec essary mortar coverage and support. CAUTIONARY NOTE : Any time notched back-trowel ing is used, the embedded thickness of the mortar cannot exceed the dry-set cement mortar manu facturer’s requirements or that of ANSI. As always, selecting the correct size of notch trowel for mortar application is a key requirement for any properly in stalled installation.

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

Photo courtesy of NTCA Five-Star member Fox Ceramic Tile

NTCA Reference Manual | 2024 / 2025

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Chapter 8 | Thin-Bed Method Installations