Many times, when new tile is to be installed, it requires extensive tear-out resulting in noise, dust and dirt, labor costs to remove the existing tile, the expense of taking the waste materials to the dump, and loss of use in the affected area. However, there is a way to eliminate these issues while yielding a very pleasing result.
The Tile Council of North America (TCNA) Handbook provides an alternative in method TR711 Tile Over Other Surfacing Materials/Walls and Floors. As seen in the attached image, the success of the 1 m (39-3/8 in.) x 3 m (118-1/8 in.) Gauged Porcelain Tile Panels (GPTP) wall installation is based on the suitability of the existing substrate, which in this case was 4-1/4” x 4-1/4” glazed wall tile and 1” x 1” ceramic mosaic tile set on a very substantial mortar bed.
The American National Standards Institute (ANSI) A108.19, American National Standard Specifications for Interior Installation of Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs by the Thin-Bed Method Bonded with Modified Dry-Set Cement Mortar or Improved Modified Dry-Set Mortar provides the following guidance.
1.6 Gauged porcelain tiles and gauged porcelain tile panels/slabs can be direct bonded to properly prepared existing surfaces/substrates.
3.4 Surface preparation process will vary based on surfaces to be installed over, consult with tile installation contractor, tile manufacturer, and setting materials manufacturer for recommendations and procedures.
5.1 Maximum allowable variation in flatness for surfaces to receive gauged porcelain tiles or gauged porcelain tile panels/slabs is 1/8 in. in 10 ft (3.2 mm in 3 m) and 1/16 in. in 2 ft. (1.6 mm in 0.6 m) from the required plane when measured from the high points in the surface.
13.1 Clean substrate and back of tile with a damp cloth or sponge to remove factory, transportation, and site dust or residue before applying mortar.
13.5 Scratch/key the mortar into the substrate and gauged porcelain tile or gauged porcelain tile panel/slab with the flat side of the trowel before combing.
13.7 Mortar ridges on both the gauged porcelain tile and gauged porcelain tile panel/slab back and on the substrate must be parallel to each other, combing at right angles (perpendicular) to the long side of the tile.
14.1.4 When installing multiple gauged porcelain tile or gauged porcelain tile panels/slabs with any side greater than or equal to 39 in. (1 m), lippage control systems are required.
The recently released (April 2023) TCNA Handbook for Gauged Porcelain Tiles and Gauged Porcelain Tile Panels/Slabs Installation, under the Substrates header states – “GPT and GPTPS are suitable for mortar beds, concrete, drywall (dry areas only), properly prepared existing tile, and some backer boards. As with traditional ceramic tile, substrates shall be clean, dry, and free from contaminants, and surface preparation may be necessary.”
On the installation shown here, the existing wall tile and mosaic tiles required a through scrubbing with a degreasing cleaner followed by the application of the mortar manufacturer’s recommended primer. The mortar manufacturer recommended A118.15, Improved Modified Dry-Set Mortar, to bond the GPTP as noted above in the ANSI Standards. Additionally, lippage control devices provided a lippage-free installation.
The installation of the beautiful black and white GPTP over the 1950’s era tile transformed this area into a sleek, clean, and modern-looking restroom. All of this was accomplished without the removal of the existing wall surface and the associated costs while keeping the restroom out of service for only a brief time. Another win for the tile industry and new tile technology.