Moisture barrier in bathroom!

[Babblas]

I am building a new bathroom in our old stone house, we will have a waterproof membrane on the floor and walls.
The room is square, three walls are interior walls consisting of brick, clay brick, and spar cement, the fourth wall is an exterior wall that is plastered from the outside and then lightweight concrete.
The floor layer suggested that I should put a moisture barrier (construction plastic) against the lightweight concrete before I screw in the studs, plywood, and drywall, before he applies the wall covering.
My question is do I need the moisture barrier?
And if so, should it be construction plastic or a vapor/diffusion barrier?

 

[SvanteC]

No. The våtrumsmatta acts as a moisture barrier, you should not have two of them.

 

[tttomten]

He might have meant the studs (not the entire wall) to prevent moisture transfer to the studs?

 

[Babblas]

Thanks for the input. I will have another talk with the mattläggaren to make sure we agree, before the carpet is put in place.