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Pre-mounting Mosaics General Overview

Pre-mounting tile mosaics can provide many benefits to the installation process. Pre-mounting creates a semi-rigid panel by consolidating multiple pieces into one that can be installed like any other piece of tile. The pre-mounting process also allows for management of tile thickness and variances to achieve a smooth, flat surface minimizing lippage. Further, the materials used for pre-mounting mosaics add crack-isolation properties to the installation. Obtaining consistent grout lines may be facilitated with pre-mounting methods. It is important to use materials that are approved for the specific installation.

If the above methods are practiced, the result will be a faster and easier installation of tile mosaics.

It is important to note that these methods are also applicable to factory-made mosaics. Pre-mounting mosaic borders, for instance, will result in a more precise installation with less mess, less effort to clean joints, a flatter surface, and easier material management. This is particularly helpful when mosaic borders are thinner than the field tile.

Pre-mounting mosaics methods

METHOD 1: FABRIC SHEET MEMBRANES Recommended for materials closer in thickness to the field

6. Flat back-trowel the mo saic piece with thinset mor tar to ensure a flat plane and compensate for any dif ferences in material thick nesses.

1. Lay out clean, dry tile pieces like they are going to be installed and use a mosaic mounting tape on the face of the tiles to se cure them in place. 2. If a mosaic is larger than 3’ x 3’ (0.9 m x 0.9 m), cut the mo saic into manageable, divided sections that can be labeled and flipped over. 3. Cut the fabric membrane (ANSI A118.10) into pieces, larger than the individual sections to be mounted.

4. Scratch coat the fabric sheet membrane with a lightweight, polymer-for tified thin-set mortar ap proved for use with the intended specific tile ma terials (glass, ceramic, por celain, stone meeting ANSI A118.15, A118.4, A118.11).

7. Lay your mosaic section on the fabric sheet mem brane and using a large, flat, and rigid tool (large enough to cover the tile), such as a beating block or a large-format tile, ap ply steady pressure on the mosaic piece to achieve a proper bond (can also be accomplished with a vibra tion tool).

5. Use a v-notch to trowel the fabric sheet membrane (trowel size can vary based on desired thickness).

Inspect the joints at the side of the mosaic panel. When a proper bond is achieved, thinset mortar will be visible in the joint at a nominal 1/3 thickness of tile.

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NTCA Reference Manual | 2024 / 2025

Chapter 5 | Material Specific Products and Installation