Ceramic tile over concrete -- floor preparation.

Old 03-03-05, 04:42 AM
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Ceramic tile over concrete -- floor preparation.

I have pulled up carpet and the concrete looks painted. does this need to be removed to get a good bond? In the kitchen area and one bath it looks like the black sticky stuff is still on the floor. What is the best way to remove these and get the best bond? the rest of the areas look like plain concrete.
I have regular thinset. I was told i could either buy fortified thinset for these areas or buy an additive that you use instead of water. whats the best way?
is the jasco adheshive remover good for the black sticky stuff and the paint?
thanks in advance for any help. John
Old 03-03-05, 10:37 AM
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Any paint or sealer has to be completely removed to give your tile a chance at staying down. Solvents can leave residue that also will inhibit the bond of the thinset to the concrete. If you use them you will have to thoroughly flush the floor to get rid of any contaminates. Scraping or grinding are your mechanical options which would be best for the tile but a backbreaker possibly for you.
The black adhesive is best removed with hot, hot water and 4" razor scraper(used on wallpaper). Get the goo up, the stain can stay. Sorry for all the prep work but I want your tile floor to last more than a year. No shortcuts here.
The modified thinset, with the additive already in the bag in powder form will be fine. One last thing, no active lateral cracks in the floor, right? If so, you will need a crack supression membrane.
Old 03-04-05, 05:26 AM
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there are some small cracks less than a millimiter like hairlines but they are all smooth and level. i also in arizona a mostly dry climate. this is backbreaking work i have found out the coating is more like an epoxy than a paint. it seems solid. i know its only on the surface because where the carpet tack strips came up is grey concrete.
Old 03-06-05, 08:42 AM
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I've had to remove that black tar from concrete before and found that the kick scraper works the best. It's really a tool used to remove vinyl tile but if you had a fairly new blade on it, it removes almost anything from a smooth concrete floor. Its like a standup shovel/spade that just has a blade on the end. You can buy one for around $20 or rent at a hardware store. Also, if the paint is not loose or pealing, you could run over it with a good sanding by using a drywall sanding extender with a fairly rough paper (60-80 grit). If you get the kind that fits the drywall extender, you can avoid being on your knees all day. You can stand up and apply a good amount of pressure to the paint. Anything that does not come up with this sanding process will be fine to tile over. Make sure you get all the dust up before tiling as dust will prevent a good adhesion for any tile job. It must be clean and dust free. Hope that helps.
Old 03-12-05, 11:54 PM
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I watched a neighbor use a combination of a scraper and laquer thinner. Seemed that the thinner did a pretty decent job of minimizing the scaper work.

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