# Black residue on slab floor?



## buildenterprise (Dec 4, 2007)

We just tore up a wet bed tile floor and are getting the floor prepped for ceramic tile. There appears to be a black adhesive or sealer of some sort on the concrete floor. What is this and what is the best way to remove it? The mortar will not stick to this stuff, the old wet bed came right up without a problem.


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## EricTheHandyman (Jan 29, 2008)

I've seen tar paper/roofing felt used under a wet bed. It could also be residue from some sort of linoleum or something that may have been removed prior to the wet bed tile was installed.

The not so good news is that it probably contains asbestos/lead/"God knows what"


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## buildenterprise (Dec 4, 2007)

This is a 2d floor concrete floor in a motel. By the looks of the "puddles" in the black material it appears that it was poured onto the concrete then allowed to dry before the wet bed was set. It runs throughout the entire 2d floor.


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## dave peffer (Jan 10, 2009)

*Black stuff?*

Age of building?
Any trowel marks?


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## dave peffer (Jan 10, 2009)

*cleavage???*

Since you say it was an old mud bed, I'm guessing it's a cleavage membrane used to keep the mud from bonding to the subfloor.
Don't tile over it. You might want to consult the architect or owner and simply do it the same way-thickbed.
If you have to remove it, don't call us!!!


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## genecarp (Mar 16, 2008)

Maybe this

http://www.integralsystems.com.au/a...epair/Primers and Bonding/TDS Nitobond EP.pdf


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## buildenterprise (Dec 4, 2007)

dave peffer said:


> Age of building?
> Any trowel marks?


The motel dates to the sixties, and this coating has been there since new.


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## JazMan (Feb 16, 2007)

It can only be one of two things. It's either cut-back adhesive residue from the original VCT or asphalt tiles that were later removed when the deck-mud was placed. Or, it's a waterproofing membrane so leaks would not ruin the guests' nite when an OOOOPS happened. 

Let me understand better. You removed a thick-bed tile installation and now you are considering doing a thin set installation? Why is that? How are you gonna account for the 3/4" - 1 1/2" of mortar you removed?

Jaz


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## buildenterprise (Dec 4, 2007)

Yes, the bed and tile were about 2" thick. There were thresholds on each side leading down to carpet which is on the same concrete subfloor. So basically the tile was just about 2" higher than the carpet, reinstalling tile in thinset would help lessen the difference between the two surfaces.


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## JazMan (Feb 16, 2007)

WOW, that's unusual for a commercial building. Is the present floor flat, with not cracks? You'll want to sell them on a crack isolation membrane system. 

So, was there ever a VCT or asphalt tiles there?

Jaz


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## buildenterprise (Dec 4, 2007)

The floor/ceiling appear to be pre-cast sections of concrete with joints every 2 feet. The concrete is in great shape. I'm just trying to figure out how to get mortar to stick to this black stuff, or how to remove it.


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## JazMan (Feb 16, 2007)

You seem to think you should get the answers you want to hear without answering the questions I've axed you. :whistling

NOW, I am trying to figure out what that black stuff is, but you are of little help. All you say is black stuff. I asked if there was ever VCT tiles on that floor. You keep avoiding the question. However, by what you just said about the sections of concrete with seams every 2', I now believe the deck mud was the original floor. AND you can NOT install anything directly to that floor without finding a way to isolate/bridge those seams. Well, they can intall carpeting. 

If you do this wrong, your customer may want to hire me in a few years to inspect and to testify against you in court to correct the mess. I guarantee you it always costs 3-4 times the original cost to rip out and do the job right, plus the loss of use of the property. If you have to ask how to do this job, you are not qualified to do it. Please stand back and walk away slowly! :thumbsup:

(The rest is for other people without this situation.) 

You remove the black stuff with a razor scraper until there is only a thin film left but you can see the concrete. The tool comes in several sizes but would be lots of labor if the area is large. looks like this; http://www.ctrentals.ca/images/5/floor%20scrapper.jpg BUT, as stated above you may as well leave it cuz you will probably not be able to go right over it. 

IF at that time the floor was suitable for tile, you would use a modified thinset that claims to be compatible with cutback adhesive, IF it is cut back adhesive. 

Jaz

PS, I see you are a deck builder. Nice decks, but why do you think you should do tile work too?


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## AboveAndBeyond (Dec 5, 2008)

i think i've run into this stuff before when i worked for a GC but never had to tile over it. i'm interested in what it is, would the O.P. happen to have any pictures?


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## buildenterprise (Dec 4, 2007)

Jaz,
I pulled up the carpet and padding from the living room and bedroom and this stuff is on the concrete there too, and there was never tile in those rooms. It looks as if it was applied to the concrete since new, there are puddles and voids in it, it's not level enough to have ever had VCT or ny tile on it. So that being said, it looks like the next course of action would be to scrape it down as you said, to try and expose the concrete. I'm thinking ditra would be called for here, I wouldn't lay the tile directly on the crete.


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## R&D Tile (Apr 5, 2005)

Probably the reason for the full mud bed over this to begin with.


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## JazMan (Feb 16, 2007)

I love Ditra, it is the best thing since sliced bread, BUT I think you have to do a real mud job just like the one you ripped out? How large an area? How many sq, ft.?


Jaz


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## buildenterprise (Dec 4, 2007)

The original mud floor was in the kitchen and bath only, 8 x 8 and 5 x 5. Now they want the kitchen tile to extend through the LR so that would add another 150 sf. I haven't even checked yet to see if the tile will clear the bottom of the metal entry door.



JazMan said:


> I love Ditra, it is the best thing since sliced bread, BUT I think you have to do a real mud job just like the one you ripped out? How large an area? How many sq, ft.?
> 
> 
> Jaz


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## rsss396375 (Aug 11, 2008)

It sounds like some type of vapor barrier which was installed in preperation for the mud, but you say its under carpet too? Here is a link to TCNA that may help:
http://www.tcateam.com/services.htm#forensic

You may want to try and take a sample and send it off to testing. Thast may cost $. Another idea may be to locate an older civil engineer in your area and describe the material to them. They may have some experience in how, or why it was used.


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