Installing Resin-Backed Mosaics Using MAPEI’s ECO Prim Grip

What are resin-backed mosaics? They are a sheet of smaller tiles that are arranged in a pattern that are back-mounted to a fiberglass mesh that is coated with an adhesive (typically epoxy-based). Resins form a non-absorbent coating on the back of the tile that regular thin-set mortar will not properly bond to.

Tile-setting materials are basically concrete. For these materials to form a bond with the back of a tile, there must be some moisture exchange – in other words, the back of the tile must be absorbent.

As the concrete cures, little crystals and branches grow from a reaction between the cement and water that is known as hydration; these crystals and branches enter the pores of the tile and create a bond. Even though modified mortars create a stronger bond, they still need some absorbency.

Traditionally, epoxy setting materials such as Kerapoxy 410 mortar and Kerapoxy CQ grout and mortar (color #00 White or #38 Avalanche) or a specialty mortar such as Planicrete W were the only options for interior/exterior installations of resin-backed mosaics.

An alternative to using an epoxy setting material is MAPEI’s ECO Prim Grip, a bond-promoting primer that can be used to coat the back of resin-backed mosaics. Once ECO Prim Grip is dry, the mosaic tile can be set using a cement-based mortar that meets the ANSI A118.11 standard or is classified as ISO 13007 C2P1 or better.