2024-25_NTCA_Reference_Manual_dig_dwnld

Mesh Mounted Mosaics in Wet Areas

The installation of mosaic tile is part of the earliest history of the tile trade. It could be said that mosaics are a part of a modern tile contractor and installer’s DNA. However, as modern methods of manufacture and installation have kept this tradition alive, new challenges have arisen that our predecessors never had to conquer, such as mounting systems used to create mosaics sheets. Mosaic sheets are causing new problems for installers. In order to have a successful installation, installers must understand the problem, potential workarounds and recommendations to rectify these issues moving forward.

WATER-SOLUBLE ADHESIVES Mesh mounted mosaics are predominantly affixed by means of water-soluble adhesives. These come in many types and forms with varying levels of solubility. There are no industry standards that cover the composition of adhesive, method of application, minimum or maximum thickness of application, amount of backing exposed, or compatibility with dry-set mortars. Additionally, since many manufacturers import mosaics or outsource the fabrication of their mosaics, tile importers have less control over the end product. Issues can go unreported, as installers in the field will in many cases just replace failing materials instead of filing a claim with the manufacturer due to the relatively small amount of tile needed and time to completion. CHALLENGES IN INSTALLATION The water-soluble adhesives may create several frustrating challenges for the installer in the field, even before they are set into place. 1. Cutting mosaics almost always requires the use of a wet saw. As the mosaic is exposed to water, it could re-emulsify and release the tile from the mesh backing. This can lead to mosaics falling apart on the saw, or in transit from the saw to the installation. With more complex designs, this can cost hours reassembling the design to install, if it’s possible at all. 2. There is also the possibility, mainly in horizontal applications or submerged applications that exposure to moisture in the bond coat could also re-emulsify the adhesive leading to the formation of a bond breaking layer between the tile and the mortar. In these critical installations such as a shower floor or a submerged application this could lead to issues well after the installation has been put into service. 3. Excessive amounts of adhesive can be present. Where water soluble adhesive is exposed to moisture such as submerged applications, steam rooms, or horizontal applications frequently subjected to moisture e.g. shower floors, this can exacerbate the potential for re-emulsification and bond failure. Leaching can occur where the adhesive might re

emulsify and migrate to the surface, creating a stain that is impossible to remove. 4. In installations where UV exposure will be a consideration, the bond strength of the adhesive may be compromised POTENTIAL JOBSITE SOLUTIONS Some contractors have resorted to remedies in the field to avoid some of these issues. These may prove to be effective in some respects, but they interfere with installation by adding time and material cost to a project. 1. Liquid or sheet membrane application to the back of the mosaic. This option may avoid the issues associated with cutting and bond breaking on the back of the mosaic. However, it still allows for exposure from the top which may re-emulsify the adhesive and release the tile from mesh backing, leading to failure due to the bond between tile and mesh being compromised. 2. Removal from mesh. Some contractors spend a great amount of time soaking mosaics in water to remove the tile from the mesh backing. While effective, this isn’t an option where mosaics have a specific design. 3. Installation with an epoxy setting material. The high bond strength of epoxy may be a good solution in challenging installation environments. Follow the mosaic manufacturers recommendations. RECOMMENDATIONS All of these issues add time, cost, and potential for failure to any project where mesh-mounted mosaics are installed. There are other methods and materials that don’t have these drawbacks. 1. Edge mounting, also known as dot mounting. This method avoids the potential problems with mesh mounted mosaics as long as the dot mounting material is not water soluble and/or doesn’t cover too much of the back of the tile. Care must also be taken with these mosaics to make sure that discoloration of the grout does not occur by having too much of the dot mounting material in the joint causing varying depths of grout and possible discoloration by not leaving adequate depth of joint to fill per the grout manufacturers recommendations. Leaving the back of the tile or stone more uncovered, sufficient coverage is much more attainable. The mounting dot adhesives used in the method may or may

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NTCA Reference Manual | 2024 / 2025

Chapter 5 | Material Specific Products and Installation