Small bathroom floor, formerly covered in asbestos tile. By the time I got the house the tile was already removed and they had peel and stick vinyl down, but didn't get the black mastic off before doing so.
Please note: I have already had an asbestos abatement contractor take samples of the mastic and submit them to the lab for testing- the mastic does NOT contain asbestos.
I want to know how the presence of this residual mastic ( still very tacky in many areas) will affect my concrete prep. I don't have any big cracks to fill and only one corner that is slightly out of level. If I thinset over the concrete (assuming it is cleaned of debris) with the mastic still there, will it compromise the adhesion?
If you think it needs to be removed- how? Or can it be covered over with SLC?
Most thin set manufacturers tell you; Adhesive residue must be wet scraped to the finished surface of the concrete, leaving only the transparent staining from the glue. To determine desirable results, do a test bond area before starting.
Read the data sheets of a few products that are available to you.
The one corner that is not flat is one too many, fix it. SLC is another option.
The scraper is a wallpaper scraper with a razor blade.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.