Replies

1. 
   stretch | Jan 10, 1999 01:19am | #1

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   Better check with the supplier of the tile and thinset--Isuspect they will tell you that the paint needs to come off where its loose so the thinset can bond with the concrete. Also determine, if possible, the kind of paint used. Concrete usually gets an epoxy based paint to aid bonding and that stuff is evil to remove. Good luck.

2. 
   Guest_ | Jan 10, 1999 04:07am | #2

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   Well, not much of a problem, although your best option is to remove all the paint and scarify the slab, as it is probably a trowel finish, ie, very smooth. If it is latex-base paint, wash the floor with liberal amounts of water. This will help pull up the loose spots. If it is epoxy, leave in place, but rough up the surface by sanding (80-100 grit).

   If the paint is oil-base you have a bit of work to do. Oil-base gets into the slab and any amount of scarifying will not ensure a good bond.

   However, if it is oil-base, I'd suggest "encapsulating" the paint. Check for any loose paint with a floor scraper and remove the paint in those areas. Sweep the floor clean, then wash with soap and water. Let dry. Apply Hydroment Ultra-Set with 1/8 to 3/16 V-notch trowel. Within 72 hours, but no sooner than 12 hours of applying Ultra-Set, skimcoat with thinset. Knock down any trowel marks--you want this coat pretty flat. Now you can set tile.

   This Ultra-Set is great for it's intended purpose, but is nasty if you get it on you. You'll have to wear it for awhile because it just won't come off, which means it's great stuff. So wear gloves, and get one of those cheapo trowels so you won't feel bad when you throw it away.

   The slab must be bone dry when applying Ultra-Set. You can set right onto Ultra-Set with thinset, but you must do so within 72 hours or the thinset won't achieve a good bond. Hence, the thinset skimcoat (it buys you some time). If you do put down a skimcoat, let dry overnight before setting tile.

   Having said all that, there is another option for you to consider: mix your thinset with a two part epoxy in place of water or additive. Any tile shop should have this.

1. 
   Guest_ | Jan 10, 1999 04:37am | #4

   *Ditto to Rich....go with the skimcoat unless it is a small area and you can tile it in one setting day. And dont worry..Ultra Set matches well with jeans, but wear gloves....doesnt go well with food.

3. 
   Ralph | Jan 10, 1999 04:37am | #3

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   My basement floor is concrete slab that has been painted. What do I need to do to it before I install ceramic tile. I'll be using thinset.

   Thanks