Many times, tile installers, both residential and commercial, are asked to install tile over questionable substrates. ANSI A108.02 – 4.1.1 says in part; “All surfaces shall be structurally sound, clean, dry, and free of oily or waxy films and all foreign matter.” Some of the questionable products include: existing vinyl composition tile or inlaid vinyl flooring installed with a latex adhesive, asphalt or vinyl asbestos tile with an asphalt emulsion (black) adhesive, cushioned vinyl flooring or painted concrete.

Some of these materials might provide a suitable substrate, but two questions remain. Can the contaminant (adhesive or paint) be adequately removed and is the existing surface material well bonded to the substrate in order to maintain the integrity of the tile installation? Let’s take a look at each one individually.

Vinyl composition tile or inlaid vinyl flooring with latex adhesive: These materials are very similar and need to follow a three-step approach. Any existing wax or polish must be chemically removed since the vinyl may contain asbestos which negates any sanding of the surface. Second, will the cleaned surface provide an adequate bonding surface for the thinset mortar? (Always consult the mortar manufacturer for written instructions and a warranty, if available). Third and most important, is the tile or inlaid vinyl well bonded to the substrate? If in doubt, walk away.

If the tile or inlaid vinyl is removed and the adhesive is removed with a razor scraper, the decision of an acceptable substrate rests on the mortar manufacturer. Contact the mortar manufacturer’s technical department to obtain written instructions and a warranty.

Asphalt or vinyl asbestos tile installed with an asphalt emulsion adhesive: The answer here is a big red stop sign. Do not attempt to remove either the tile or the adhesive.

Cushioned vinyl flooring: Cushioned vinyl may have been installed in one of two ways: loose-laid or glued down. If loose-laid, roll up the vinyl and treat the substrate as needed to meet the mortar manufacturer’s guidelines. If the cushioned vinyl is glued down, it must be removed since the cushioned surface will not adequately support a ceramic or porcelain tile installation.  Before removing the vinyl and depending on its age, it would be wise to consult a vinyl flooring expert to determine if it contains asbestos. If it does, an asbestos abatement professional should be hired to properly remove it. If it is free of asbestos, treat it in the same manner as described above for vinyl composition tile.

Painted concrete: This is the real sleeper in the group which may fool you into a thinking that it is okay. The paint seems to be well-bonded and is not cracked or peeling, but is it bonded well enough to provide a long-lasting tile installation? The included image of a painted concrete floor, which the homeowner wants to cover with porcelain tile planks, has several layers of paint. If you look closely, you will see the outline of what appears to be flagstone. The original owner had the painter place ½” masking tape on the floor to create the flagstone pattern, paint over the tape, and then remove the tape. Subsequently, another coat of paint was placed over the flagstone pattern. Now the question is, will the paint stay bonded to the concrete? If it does, all is well. However, if it doesn’t, the installer has a failure on his or her hands which will require the removal of the tile, mechanically strip all layers of paint and install new plank tile for free.

Before you say I guess it will be okay, seek the help of the mortar manufacturer for guidance. And remember, it is okay to say no thank you and walk away.