Paint basement (white bathtub)

Good day everyone.

The outer walls of my basement are concrete as a white tank and the inner walls are built with aerated concrete blocks. All unplastered. I just want to paint everything white. I actually wanted to use the same white as in the rest of the house, a nice glossy white. At the hardware store I was told that I can only use a matte white, but I unfortunately forgot the reason. I think it was something about moisture or something like that. Is that correct?

They think that your glossy paint is something like latex paint - therefore they think you should use matte. But you don't have to - although the fewest want glossy and it usually doesn't look good.

I cannot confirm that. The [Weiße Wanne] is only there to prevent water from entering from the outside. Therefore, you will not have more moisture inside and can plaster and paint your walls as usual.