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Old 12-31-2008, 09:50 PM   #1
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Remove mastic/adhesive from concrete?

I just bought a 1950's house in Cleveland. There is a 4x4 entry area that was linoleum over some kind of core board adhered directly to concrete. The floor refinisher guy sanded down a small spot just far enough to determine there was no wood.The lino came up easily, the core board is difficult, and the adhesive is rock hard.
I would like to stain the concrete in this area, as well as in the 1/2 bath down the same hall. The 1/2 bath has 3" hexagon tiles have no mesh backing and are adhered directly to concrete. The one tile that came up has concrete stuck to the back.
Any advice on how to take up the tile and adhesive? I know I'll have to put an overlayment on the concrete before I stain it, but I'm expecting some divots. I guess it would be easier to just tile over, or have the tile in the bath painted, but the stained concrete will look pretty cool. Thanks for any info you can give.


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Old 12-31-2008, 11:22 PM   #2
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Originally Posted by FixyChik View Post
The lino came up easily, the core board is difficult, and the adhesive is rock hard.
Any advice on how to take up the tile and adhesive?
I have removed hard mastic from plaster walls many times, and the best way I know of to do this is with a Nestor scraper (named after it's inventor).

You grip a single edge razor blade in a pair of needle nose style locking pliers. Hold that tool upside down so that the long nose of the locking pliers holds the blade at a shallow angle for effective scraping. Heat the mastic with a heat gun and shave it off the concrete when it's soft with the scraper.

Wear a leather work glove on the hand holding the scraper cuz that scraper will get pretty hot.

If you find the razor trying to "dig in" to the concrete, just dull the sharp edge of the blade with sandpaper.

Concrete is a porous material, and staining it requires that you remove any residual mastic from that porous surface. I'd be concerned that whatever solvent you tried to do that with wouldn't remove the mastic completely, and you'd end up with a "ghost image" of the mastic on the stained concrete.


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Last edited by Nestor_Kelebay; 12-31-2008 at 11:29 PM.
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Old 03-19-2011, 09:18 AM   #3
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Scraping Idea

I am also facing this infuriating and extreme-effort task in preparation for tile laying. Chemical removers are great for getting the last bits and thin coats off the 'crete.

It is best to get the majority of the stuff off first. Many times floor scrapers just can't get a good bite or require major effort to get hardened/fused mastic off. I grabbed a small plane (so it follows the surface undulations), adjusted the blade protrusion so it just slices the mastic. This makes the blade go further without lots of sharpening. It also allows you to bear down significantly to get a purchase on the "bullet proof" surface.

This done, the final removal and sanding (I'm looking for 15-grit belt sander paper ) is much more effective. Great weight loss program for sure!

Warnings: Make SURE you're working on non-asbestos flooring! Breathing this stuff is a killer. Also, using very hot water rather than certain chemicals is generally better if you're planning to use any thin-set (for tiling), as they may leave residues that can inhibit adhesion.

Last edited by brused_thumb; 03-19-2011 at 09:40 AM. Reason: asbestos and mastic concerns
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