Painting above tub tile

[Tbucket]

I'm putting in a bathtub and want to do tile up to the shower head and paint above that. Right now I have CB board up to the ceiling with the joints filled with alkali resistant mesh and thinset. I plan to redgard (no vapor barrier behind CB), do I redgard up to where the tile will stop or go all the way up to the ceiling? Do I use drywall mud above the tile so I can paint? Will drywall mud stick to redgard or the CB? Is drywall mud the right stuff to use to smooth out the surface for paint?

 

[Jadnashua]

Drywall mud won't stick well to RedGard, I don't think (been awhile since I read their instructions!). The vapor barrier is needed for the wet areas. Above the shower head is not considered a wet area. I'd stop the RedGard so it was only underneath the tiled area, then you can use mud to smooth the cbu surface, if needed and paint it.

Now, a setting drywall mud MIGHT stick to RedGard. The stuff you buy in a bucket won't reliably.

When cement based products cure, they literally grow pointed crystalline structures that poke into microscopic irregularities and that's what causes the bond...it's not a very adhesive bond, it's a mechanical one. Now, if you use a modified thinset, that will have some adhesive characteristics in addition to the mechanical bond of the cement.