Wall Tile Over Painted Wallboard?
 

Here is an odd one: Been asked to tile (6x6) over cement board on an exterior wall. No problem until they said they had painted the wallboard!

How should I prepare the board? Angle grinder with a sanding disk or wire disk? I plan on using unmodified thinset . . . is that the strongest?

Not so good----Grinder with a wire wheel to scuff well----unmodified with liquid additive is the strongest-Kerabond and Keralastic by Mepei is a good example.

A high quality modified thinset should do it.

What brand is the cement board?:)

Yeah just scuff or sand any sheen off of it. Not a big deal painters are routinely ahead of us on jobsites and they always overspray. Don't use unmodified mortar, your situation needs latex modified mortar. All tile-concrete board installations use modified.

I want to see the answer to Bud's question.

Jaz

So does Bud.

What brand is the cement board?:)

either keralastic or granirapid are WAAAAAY stronger than unmodified thinset



other than that, you can use a drywall sander if you really want to. just knock the sheen off. make sure you get any loose dust away in the process. as long as the paint is well-bonded, the mortar will be too.

i used to do a lot of tile on military bases, and in the name of things looking right for the people with the funny hats, a lot of mistakes like that were deliberately made all of the time.

Keralastic is a brand of thinset? Why am I so confused?:)

Keralastic is a polymer reinforced thinset offered by mapei. They also sell the liquid latex that you add instead of water.

IT IS STRONG! if you have some spooge left over after setting a lot and you don't get it within 24 hours, it is almost impossible to break off with a 5 in 1

Yow I know that, :yes: I was trying to be gentle with you.:)
It wouldn't hurt for you to mention that Keralastic would be mixed with unmodified thinset to complete the thinset concoction.

man, i did that once on fort carson, and my boss freaked out! i tried to say, "don't worry about it, man" and he wouldn't have it.

i'm glad to hear someone else say it. i wish he was on this forum.