We are about to install 16” x 16” terrazzo cement tile (2cm) on a 10′ x 10 wall in a doctor’s office. The wall is a painted sheetrock. Can we install over the sheetrock using a bonding primer or would it be better to install over a cement backer?
The NTCA Reference Manual lists paint as a questionable substrate.
It may likely be better to install over a substrate that does not have paint beneath the bond coat where the bond of the paint to the substrate must be relied on to support the installation.
Some manufacturers have mortars or primer/mortar combinations that will bond to a variety of questionable substrates including paint. Consult your tile and primer manufacturer for their recommendation for adhering this particular tile to the substrate.
Also be certain to check with the tile manufacturer to understand the required minimum deflection criteria for this type of tile. It will be at least L/360 or higher.
The introduction of increasingly rigid OSHA guidelines have lent even more credence to the popular trend of utilizing backerboards that promote both health and safety. Those working in the industry are concerned with protecting their health during installation, as well as protecting the end user against any exposure to contaminants later on.
Many professionals now choose state-of-the-art, cement-coated foam-core backerboards, which contain very low silica while providing a high-performance cement bonding surface. Professionals are also being warned to be aware of other substrates of concern, including formaldehydes and non-polymeric flame-retardants such as HBCD.
1 Progress Profiles
The company’s Profoil Panelis an extruded polystyrene panel with a density of 48 kg/m3, provided on both sides with a waterproofing membrane. Panels are
36” x 60”/106” (91.5 x 152.4/270 cm) and available with several thicknesses. They are designed and tested to have mechanical resistance and long durability, allowing work to be carried out quickly and inexpensively. They are suitable for indoor application with a thermal insulation function on floor, wall and ceiling. Profoil Panels can also be used for partitions walls, tops for kitchens, shelves and different furniture. progressprofiles.com
The company’s original Building Panel is constructed of a high-density, closed cell extruded polystyrene core and reinforced with an ultrathin cement resin surface coating, resulting in a lightweight yet sturdy backerboard. Internally water- and mold-proof, it is part of the wedi Shower System. wedicorp.com