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Old 07-10-2008, 03:36 PM   #1
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Black Tar On Basement Floor

I am remodeling my 50s ranch basement. The old floor was some kind of laminate tile that looked like it used tar to seal to the concrete. I scraped it all off and now I still have a very thin layer of black across the floor. I am not exactly sure what it is but I would like to tile over it.

What exactly is it and how can I remove it?



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Old 07-10-2008, 04:59 PM   #2
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It could be "black asphaltic adhesive". Black asphaltic adhesive, also called "black out" was commonly used from the 1950's to 1980's to lay vinyl composition floor tiles and asphalt tiles.

That's about the only thing that I can think of that fits the description of "tar" that would have any business being on a concrete basement floor.

YOU CAN float over this stuff with a cement based floor leveling compound, but there are ways to remove it fairly quickly and effectively. Post again if you want to know a relatively fast easy way to remove the stuff.

But, just to confirm it's black asphaltic adhesive, take some paint thinner or mineral spirits on a paper towel and wipe it on that black stuff. Did the paper towel turn black? If so, the solvent is dissolving it, and it most likely is black out.


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Old 07-10-2008, 06:38 PM   #3
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BLACK OUT? Never heard it called that before and I've been in the biz since 1964. It's "asphalt emulsion" usually called "Cut Back".

Anyway, you should NOT try to remove it since it's impossible to get it all off and the solvents could cause an explosion. Even if the house does not blow-up the solvents will be driven deeper into the concrete creating a bonding problem.

You didn't mention what type of tile you want to install. If it's VCT, you can use the same type of adhesive and go right over it. If you're installing ceramic tiles, there are many thinset mortars that are rated for going over "Cut Back".

TILE GUY - retired- TROY, MI - Method & Product suitability consulting.

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Old 07-10-2008, 08:30 PM   #4
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Where I live, they call it "cut back" too. It seems there are about a half dozen different names people call this stuff by.

I wonder about what's going on in this forum. People are concerned that any use of a flammable solvent creates an explosion hazard.

If you read the MSDS info on most solvents, you'll feel dizzy and nausious and get headaches and sore throats long before you even approach the minimum flammable concentration. If you follow common sense procedures like providing for adequate ventilation and not smoking while working with highly flammable liquids, you CAN reduce the risk of your house blowing up.

I mean, where is it written that DIY'ers always do things in the most hazardous way conceivable? The reality is that most DIY'ers are well aware of the risk of a flammable vapour explosion and will provide adequate ventilation so that the workplace never even comes remotely close to containing a explosive concentration of vapours.

Last edited by Nestor_Kelebay; 07-10-2008 at 08:44 PM.
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Old 07-10-2008, 09:02 PM   #5
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I only ever heard it called cutback as well,and this dating tells me it contains asbestoes, Asbestoes was not removed from the cut back until he late 70s, but it was still on the shelf in products until the new batches were brought in, it was never recalled it was just removed.Same with the tile that is why there could be asbestoes in tile installed even until the early eighties.

The tile also contained asbestoes but it was the lowest form of asbestoes ever brought to the market. The reactivation of it can only be brought on by sanding it or scraping on it.

This why abatement companies have been making millions with removals they use a wet method that keeps the dust down and chemicals that liquify the cutback.

Cutback has haunted the flooring industry for years it repels bonding agents in almost every glue they make and when they took out the asbestoes, the glues that had it stopped having thier own bond, it was a nightmare until they started to produce better glues this inturn brought on many inconsistanies that still will come to bear on many jobs from that era.

It will also impede the bond of thinset, the advise method is to get enough bare concrete surface for the thinset to pentrate, use top quality ultraflex.

Of course Ditra solves this problem as well!
Ditra escapulates the cutback under it and it is applied with a dryset mortar, this does not contain latex (latex will reactivate cutback) and the limited body will form a suction bond with the concrete. If any release occurs the Ditra will become a slip sheet and the movement will not transfer to the tile.

This why I sell Ditra it is the magic bullet, the Germans have known this for many years we are just finding it out
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