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My original aim was to end up with a, possibly stained, clear-coated cement floor. After removing old floor tiles, I rented a floor grinder which took care of most of the old mastic. There were still thin spots that remained, so I bought some product at HD that softened the spots for removal, but as others have said, made a friggin' nightmarish mess of it! Will the residue prevent sealers or other coatings from absorbing into the concrete floor? If so, would thinset even stick to these areas? I don't want the expense of tile, but I've about had it trying to clean up this tar-like mastic to clean and clear-coat this floor! Any suggestions? Thanks, Bill

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I had an entry way floor some 30 years ago that had old hard vinyl tile glued down in it with the blackish-brown type of adhesive. I wanted to replace that tile with a ceramic floor tile so I peeled out all of the old tile. I then used a wide razor scraper to get most of the old adhesive scraped off.

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After that I purchased a few gallons of aggressive paint stripper, opened every window in the house, shut off all gas appliances and pilot lights and poured out a layer of the stripper across the whole floor.

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I let it sit for a suitable time (may have been about a half hour or so). Then working some with a wire brush and metal dust pan as a scoop I took up all the goop off the floor.

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Finally using a bucket and a large sponge I washed up the whole area with a copious amount of hot water to remove all the stripper residue.

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After the floor fully dried the surface was the nicest clean concrete surface you could wish for. I was able to put down the tile setting cement and had no problems with it adhering to the concrete.

  • Thanks for description and pix of supplies. I've tried all this. Adhesion with thinset (cement) to the existing cement floor would be no problem, but preparing the surface for paint adhesion requires additional steps explained in the first comment, above. Thanks, again ~ – Bill May 4 '16 at 15:33
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Do you know what base the adhesive is? I.E. latex, mineral spirits, lacquer? you could try paint stripper, lacquer thinner, (be careful with flames or sparks), or something like Goo Gone, or Goof Off.

  • Thanks, the stripper, while removing a lot of the mastic, just smeared a thin layer over more area, forcing me to have to grind and sand more. – Bill May 4 '16 at 15:26
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I used bean-e-doo from Franmar mastic remover.The company was bought by "Bear". It works like a charm and very easy to use. It's also environment friendly as it is made out of soy bean (virtually no smell). It costs about $35 a gallon. The amount to use depends on the surface and the thickness of the mastic.
I hope that helps.

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I had old tile adhesive on my concrete floor. I used a wall paper steamer and a 4" floor razor and about 25 blades for a 50sq ft bathroom. Got 95% of the adhesive up. Not concerned with the remaining 5%. I'm going to lay ceramic tiles.

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clearing a concrete slab is an entirely different process than using it as a base for some other flooring the key is homogeneity.

to achieve that, on a previously adhered to floor, is to coat it with a layer of new cementious material. just trowel on 1/4" or so of a good high polymer modified levelling compound (not a self levelling compound) or a tile mortar (flextile 56 or dyna ceraflex 620 works great for this). let cure and then put down your stain/stains/topcoat. try to get a topcoat that has the aluminum oxide in it - they wear far better, but they are more money and harder to apply.

you can skip this step if the old flooring was tile or something un-adhered to the concrete, but if what was there previously used any kind of adhesive (as opposed to a mortar), you will get terrible results. the surface pores of the concrete will be irregularly sealed with the adhesive, even if you use an acid etch or a chemical stripper to remove it. thats going to give you a very blotchy and heterogeneous finish on the final coating. and if you use a topcoating paint instead of a stain, it will adhere poorly where those same residues are and wear through differently over time.

this is all assuming you want a clearcoat on top, and not just a paint. if you want just a painted floor, then just strip and paint - just use a good two component epoxy for best results.

  • Thank you for your time and attention to this challenge, and for sharing your expertise. Because of not getting the residue off 100% (leaving some intermittent traces) I have decided to paint rather than clear coat the floor. Although I've seen many commercial floors stained and clearcoated that look okay without a cementitious top layer, but they may have not had mastic on them (I suspect some have), or they will, over time, run into problems associated with finish non-adherence also. If I run into stain bleeding I will eventually have to take your advise and trowel on the cereflex 620! Thanx – Bill May 4 '16 at 15:22
  • just remember that if you paint, no matter what you put on, it will eventually wear through and look its age. thats one of the reasons clearcoats are used - as they wear, the concrete below is all you see. in most commercial installs, there is regular application of a clear acrylic sealer. this keeps up the spots where the original clearcoat is wearing through, and thus, the overall aesthetic of the floor remains the same. once you paint, ... – personal privacy advocate May 4 '16 at 15:44
  • ...you are committed to repainting for the rest of time. if you are looking for the best looking, longest lasting floor, put lots and lots of coats of epoxy down with alox additive for wear resistance. or trowel on mortar, then stain and clearcoat, followed by regular applications of clear acrylic topcoat sealer. good luck – personal privacy advocate May 4 '16 at 15:44

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