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I have a large basement in a split level 1960s home with old 12 x 12 linoleum (likely asbestos) tiles on concrete slab. The total area is around 450 SF. I would like to put in a slate tile floor, ideally by leveling the floor then using Ditra. The linoleum tiles come up very easily without much fuss, so I don't mind donning a respirator and bagging them up for proper disposal. What worries me is the glue underneath, which also likely has asbestos in it.

Can I encapsulate it or cover it with a leveling compound? I need to level dips and imperfections in this floor anyway. Is there any product that will adhere to the old glue? I'd love to no have to worry about scraping it up.

Here's a close-up picture where two tiles came loose. I have done tile floors before, but never had to deal old asbestos linoleum this before this house. Any recommendations are appreciated!

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    Unless you need the extra fractions of an inch of headroom you'd gain by removing the tiles themselves, why not just pour the SLC over the existing tile? Encapsulation is one of the recommended ways of dealing with asbestos and it's much easier and less costly than removing it.
    – FreeMan
    Dec 17, 2021 at 14:04
  • I had considered this but was worried about the bond to the existing tile. If I encapsulate with SLC, how thick of a layer would be necessary for encapsulation and durability for a tile floor above?
    – sc_props
    Dec 18, 2021 at 15:09

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The answer to your original question is no: this type of tile adhesive is known as "mastic" or "cutback", and if you carefully check the directions for most leveling compounds, they will specify that mastic or cutback must be removed prior to use.

That said, I recently dealt with removal of asbestos tile and there's two other approaches you could potentially take:

  1. The mastic may not contain asbestos and can be removed with solvent and scraping. The only way to be certain is testing, so you should get the mastic tested. If clean of asbestos, you can use a combination of adhesive remover formulated for cutback and a mechanical scraper to remove it. This can be difficult if the underlying concrete was not flat. If the mastic does contain asbestos, you'll never get it off without it becoming friable and requiring extensive safety measures to legally remove.
  2. Per FreeMan's recommendation, encapsulation is a much easier approach. Bury it tiles and all and never deal with it again. In this case, it won't matter if the mastic has asbestos or not.
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  • Wondering how thick the SLC layer would have to be to encapsulate and provide solid footing for tile? I have not had the floor or glue tested, but based on my research and the age of the house I am nearly 100% certain that both contain asbestos.
    – sc_props
    Dec 18, 2021 at 15:11
  • Honestly no idea on how thick to go with SLC - in my case, there was carpet glued directly to the tile, and the mastic did not have asbestos, so I went with an abatement contractor to remove the tile (friable since it broke as it was removed), and dealt with the mastic directly. Tile was 50s-era, so you might be surprised on the mastic. I'd still recommend testing it, it only runs around $50-$100.
    – kg333
    Dec 19, 2021 at 17:56
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    Interesting about the non-asbestos mastic. Thanks for the tip. I think I will have it tested. I also came across a product called Perfect Primer, which can apparently seal in asbestos cutback glue prior to application of SLC.
    – sc_props
    Dec 19, 2021 at 20:29
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I'm looking into the same sort of thing in my house, and as I was reading into the instructions for LevelQuick RS, it does specifically state in the instuctions that a suitable substrate is "Cutback adhesive residue." So if you prime the mastic with their primer and then pour the leveling compound over all the primed residue, based on what I am reading it would be an OK solution.

Also, since this is a fairly old post, if you have already taken care of this, what did you end up doing?

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  • Thank you so much for the info! As a matter of fact, I have not started this project yet. It's down the list of a few other things. I'm also considering a floating LVP floor over the existing tile, which would still require leveling but adherence is less critical since the floor floats, as opposed to real tile.
    – sc_props
    Feb 9, 2023 at 17:53

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