Vapor barrier against slightly insulated interior wall?

[Carranor]

Hello,
we have had a bathroom renovated on the upper floor and we took the opportunity to tear out a sauna that came with the bathroom. The sauna space makes the adjoining bedroom a bit larger.

Now I have some questions about the vapor barrier. I have installed a vapor barrier on the ceiling and on the side walls that go towards the outer roof.

Do I also need to put up a vapor barrier on the wall that has a bathroom and ancillary room behind it?
The ancillary room is somewhat insulated so it might be considered as "indoor environment"?

Then I had a thought about painting with moisture-resistant paint in the bedroom in case I have fatally failed with the joints for the vapor barrier. Can I do that?

See attached image.

 

[anders07]

No, not a vapor barrier in the interior wall. Also, do not paint with wet room paint, it makes no difference for the moisture inside the wall/insulation. Regular wall paint is quite dense too, but what you want to prevent with a vapor barrier in the ceiling is moisture reaching the wood/boards indoors.