Can cement board extend beyond the tiled area on bathroom walls?

Question

I have this layout and all the areas marked with green will get tiles I am not sure about the area around the window (marled with diagonal green lines)

The area I have doubts about is the area above the green line at the bottom of the mirror. I have cement boards that would cover that entire wall (2 sheets less than 8' long)

From what I am reading the cement board could be painted over, or more accurate said, certain types of cement board

What would you recommend me to do in this case ? Should I transition to drywall in that area behind the mirror ?

Answer 1

You can skimcoat it with drywall compound (mud) and then paint.

You can also just paint it but it will look very different from paint on drywall.

Answer 2

You do not need to protect the entire bathroom with cement board, no.

However, the cement board and tile should extend past the tub/shower at least a little bit so that drywall isn't the first victim of excess water splashing out.

Per:

• https://www.homerepairtutor.com/cement-board-installation-part-1/
• https://www.familyhandyman.com/project/cement-board-ceramic-tile/

Notice how the tile goes past the glass door.

If you did cement board the entire bathroom then you could apply drywall on top of it and end up fairly flush with the tilework. You will of course have to use cement board screws to attach the drywall so things could get expensive. You'll still want to extend the tilework beyond the tub-shower for the aforementioned reasons.

Answer 3

You can finish cement board just like drywall. It's a little more difficult due to the rough texture, but a couple skim coats and you're all set. Keep in mind that the use of regular drywall mud over cement board would defeat the purpose of using cement board for those locations. Use setting-type joint compound where you expect regular moisture.

That said, I'd transition to drywall anywhere I'm not tiling--ideally just inside the edge of the tile. This makes finishing easier, not to mention installation. Cement board isn't fun to work with. A quality primer and topcoat will alleviate any occasional splash concerns.

Answer 4

The other answers are more or less right but missing some important details.

1. You do not want exposed cement board to extend out. The goal should be for the tile - even 1" - to lap over the drywall next to the cement board. Remember you don't need cement board outside your doors and things like that.

2. What if you have to have "exposed" cement board. Yes you skim coat it. But if you use latex pva primer and latex paint - which most people on here would suggest - your skimcoat will crack and fail within a couple years if that long. You must must must use an oil based primer to provide a moisture barrier for the 1/8" skimcoat. After that you can go latex or oil on top of it.

After finishing over 100 bathrooms I can say the #1 thing to longevity of the look and feel is using an oil based primer. It is funny your question is exactly why I started using it. We got these shower kits that were thin sheets of marble (not faux marble). Everything had to be almost exactly plumb/square and called for concrete boards backing... We just decided, so there wasn't a gap to run the boards to the ceiling (~9') when kit was about ~6'.

So skimcoat the upper area, prime, paint. Every fricking unit that we did this bathroom - paint/skimcoat failure. Older guy in our crew cleans up the first one... Asks me what type of primer. Explained to me how oil based primer prevent steam moisture from penetrating. Reduces these kinds of issues, nail/screw pops, wet spots and almost every other kind of bathroom issue. Never primed another bathroom in latex.