Tiling over painted concrete block?

[CAMAN]

My boss wants me to remodel the restrooms at work. One thing he wants is tiled walls. They are currently concrete block with 4+ coats of gloss epoxy paint on them. There is no peeling of paint so I believe it is sticking well and won't cause any issues. They are two fairly big restrooms with a lot of surface area to cover, so is there any way to do this without sandblasting everything? I figure I need to rough up the surfaces well with a wire brush, but what after that? Did a little research and each HSOforum said a completely different thing. Either absolutely not without sandblasting everything, to just roughing up the surface and using a highly modified thin-set, or roughing the surface applying a scratch-coat then a mastic.

Is there any proper way or should I tell him to just paint? These are public restrooms also, so they need to be durable.

Thank You!

[Stratosman]

I wouldn't do it without removeing the paint...Can't guarantee a good bond to the paint, hate to have it fail and look like a fool in front of the boss right...

[Eelpout08]

would putting cement board over the existing wall be an option?

[theiceman]

What I've dome is just take a palm sander with really coarse grid sandpaper and go over over the paint. Then clean it really well. 40 grit should work.

[Gordie]

You dont want to put the mud dierctly on the paint it might bond for a while but it will let lose.

The scratch coat with a bonding agent is a possiblity but I would be affraid of the paint to the block bond more than anything with the extra weight of the mud and the tile it could give you problems.

IMO the best way to do this would be to put a dura rock style backer board or fiber board they make several thicknesses and you could get by with the thinner stuuf just glue and screw it off.

Use a tapcon concrete style screw and a good adhesive and you shouldn't have any problems.

Another thing you could possibly do if the paint is in really great shape and no peel or craking is present is to use a tile adhisve to set the tile right to the paint then just grout the joints but this something I wouldnt recomend if you are a novice at tile laying and you still have the possibility of the paint to block failure.

I think there is probably to much paint on the walls to do this sort of application.

[CAMAN]

Thanks guys, I was thinking about using something like Durock also, but that a TON of drilling and screwing into concrete. But it is an option, and I have been looking for a good excuse to buy a new hammer drill.

I'll probably go talk to a few pro's at the tile shops to see what they may recommend and maybe even make a few calls to manufacturers.

Quote:

hate to have it fail and look like a fool in front of the boss right...

I don't need failing tile to do that!

[cavalierowner]

If you talk to the folks at the tile shops, make sure it's someone who has worked in the industry. I once actually had a young guy try to convince me to use premixed tile adhesive in a shower! In addition to talking to the pros, I would suggest talking to the manufacturers reps for suggestions on what to do. I believe H.D. carries Custom Building Products and Menards carries Mapei. Both manufacturers have good products that I used to see on jobsites all the time and they have been helpful to me in the past (particularly Custom).

[Stratosman]

I know the local Rep for Custom well and have his phone #.... if you want it let me know.

I second the comment about "pros" at some shops... they aren't the ones that are gonna warranty the installation. Go right to the manufacturer....

[IamZombie]

What about a wire mesh like they use for stucco?

Or if you frame it out like you would finishing a basement?

Then put Durock on the framing.