Q: I have removed vinyl tile in my kitchen and there are sections of wood that are black and sections that are clear on the same sheet of plywood. I can detect no moisture on either. Is the black mold dead? I am going to retile with vinyl. Is there anything that I need to do before that?

- Walker Baird

A: Your next steps really depend on the extent of the problem present. A few things to consider here:

(1) If the black material is mold and it is dry, it may not necessarily be ‘dead’. It is advised that prior to the application of new tile or tile mastic (glue), the surface should be completely disinfected with a disinfectant biocide solution.

(2) Additionally, you should consider the fact that if there is mold, there must have been a water leak that caused it to grow. Has that leak been fixed? The mold most likely was feeding off the vinyl glues present on the tile.

(3) If there was a prior water leak, you should make sure the plywood sub-floor’s structural integrity has not been compromised by a chronic water problem.

It is advised that if there was a chronic mold problem that may have affected the sub-floor, you would be best served by contacting a local mold remediation firm to address the situation. They can address removal of the mold and the sub-floor concerns.

(4) You may not be viewing mold at all. Many vinyl tiles are adhered to the plywood sub-floor using ‘mastic’ which is a glue specifically used for this purpose. If it is mastic, and not mold, you should treat it carefully as some mastic does contain asbestos. The safest method to address this, other than removal of the mastic by a licensed/trained asbestos removal contractor, is to not disturb the existing mastic but to apply the new vinyl tile glue directly over it.

A sample of the black material could be submitted to a laboratory for analysis for mold and asbestos content to give you a better idea of  the material you are dealing with.

Answer provided by Keith W. Pokorny, Senior District Manager of EFI Global.

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