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So I am wanting to turn my tub only area into a tub and shower and because of this I am wanting to tile the entire surrounding area with tile.

The big question I have is if the wall has latex paint, slightly glossy, and I put water-proof membrane over it, is that strong enough to hold in the wet area? I have coated a small area and the hold it strong, it takes a sharp edge to break the membrane, can't just pick at it with my nails, and it doesn't peel off the entire area after breaking it.

The water proofing Mapei Mapelastic™ AquaDefense.

The wall underneath is solid, I can't say it is a CBU but it is some mix of hard materals, very corase, as it ruined my metal saw blades fast when I have to move and outlet over.

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Could you? Sure. Of course, you couldn't know how long it will last/continue to adhere to the latex though (may not be an issue). Here's the technical data sheet‌​. Personally, I'd rather spend the little bit of money it would cost to replace with new cement backer, but that is a personal philosophy of wanting to know I tried to do it the best/longest lasting way I could at the time, for the money I had. @DMoore suggestion isn't a bad one though. When in doubt, call the company and ask for their input. –  Jacob S Oct 2 '13 at 15:33
    
what are your walls made up of? Sheetrock? –  DA01 Oct 2 '13 at 17:12
    
@DA01 I can only confirm the material is very hard and corase like concrete. When I was removing a piece to move an outlet it removed all the teeth from a metal blade and scratched my hands up pretty good. The home we built in the 50/60's (don't remember exactly which one currently) –  Justin Oct 2 '13 at 18:51

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I have applied thinset over paint many many times. I mean they have waterproofing paint (redgard) now and you thinset over that. Now the question is did the paint cure and does it have a good bond to the surface? If you don't know that then mix a little thinset, put up one tile (where you will eventually want it), and test it out. If it is solid the next day then you are good to go.

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Are there any other ways to test other than placing a tile up? EG trying to chip it away and see if move than the chip comes up? –  Justin Oct 2 '13 at 15:57
    
Well it sounds like your walls are some form of concrete - which I just took out a 50 year old shower with similar walls. If you chisel at the concrete hard enough it will chip. Not sure what test can be done. Thinset will stick to latex. How well is your latex sticking to your concrete? Also you can get a wire brush and give it a really good scraping and that is a 20 minute deal. –  DMoore Oct 2 '13 at 16:47

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