QUESTIONI recently had a contractor cover my very old, terra-cotta stairs (treads and risers) with concrete slabs and tile that look and feel like rough granite. Now I want to install Mexican talavera tiles on top the risers, leaving the "granite-look" treads alone (yes, they overlap the risers). Can I adhere the talavera directly onto the existing risers, or do I need to prepare the surface in some way? Should I use special adhesive for this application?
ANSWERANSWER - It is possible to adhere Mexican Talavera glazed decorative ceramic clay tiles to a concrete tile surface. Not knowing if there is a sealer or stain or some other coating or contaminate on the existing concrete tile risers, it is best to scarify the concrete tile risers first.
You can scarify the concrete tile risers with a grinder to abrade the surface. Make sure that afterwards that the clean concrete tile surface readily absorbs water. Then use a modified thin-set mortar that meets at least ANSI A118.4 performance standards to bond the tiles to the clean and dry concrete tile risers. Be sure to have a silicone caulked/sealant movement joint at the top of the riser and the bottom of the riser to mitigate movement. Be sure to follow the product manufacturers' directions for using the various installation products.