Remove Ceramic Tile Mastic on Concrete


Old 06-28-03, 08:44 AM
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Exclamation Remove Ceramic Tile Mastic on Concrete

I have removed all of the ceramic tile on the bathroom floor of my 40-year-old home. It appears that there is a layer of concrete-like substance (mastic) left on top of the concrete. I believe this is the case because there is a flat, 3" border of of concrete around the edges of the room that is about 1/2" lower than the rest of the floor and smooth concrete (unlike the rest of the room which is rough (mastic?).
However, when I try to bust the rough surface (mastic?) off, I do not reach a flat surface. I simply make deep divots. I am afraid that I am simply busting through the mastic AND the concrete. I cannot find where the mastic ends and the concrete begins.

1) Is my assumption right that this is mastic on top of concrete?
2) Is there a recommended way to remove the mastic without busting the concrete?
3) If I cannot do so, is it ok to lay new tile over the old mastic?
See pic attached
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Old 06-28-03, 09:03 AM
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Sounds like mortar, not mastic. And you're going to use mortar too, not mastic, to lay your new tile.

You don't have to get 100% of the old mortar off,but you should get most of it off. If you damage the concrete a little, it's not that big of a deal.
Old 06-28-03, 10:03 AM
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you could even use an engineered concrete[self leveling]to smooth over what is there already,the problem with continuing to tear out and smooth the concrtete over is that you may end up at the end of that process going over it with something anyway to smooth over all the holes left from trying to smooth it out,did that make sense?you may be better off leaving what you have and pouring a self leveler over it,ardex k-15 come to mind
Old 06-28-03, 12:15 PM
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Floor cleanup after removing tile

I just removed about 100 sf of old thinset from my den. What I used was a wall paper scraper with replaceable blades. Its slow but does a very good job. Tom
Old 06-28-03, 08:01 PM
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I think that you are right John. I have never seen mastic, but I heard that it is white and doesn't look at all like concrete. What I have looks like concrete, so it must be mortar.

Floorman, the self-leveling idea sounds like a good one. My only concern is that I will build up the surface too high if I don't at least reduce the height of the mortar that is already there. Does grinding 1/4 to 1/2 inch of the existing mortar down and then using the self-leveling stuff sound like a good idea?

Any ideas out there on the best way to reduce the height of the existing mortar? Is grinding the best way? This material is almost as hard as concrete.

Thanks to all for the help
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