Building on an insulated wall - do I need a moisture barrier?

[Prosit]

I have slanted ceilings on my upper floor and want to make a wall a bit thicker to create a "hidden door" to access the not-so-attractive hatch to the catwalk.

I was thinking of installing some studs on the inside of the current wall, insulating with something suitable (soundproofing), and putting up drywall or particle board on the inside. The part of the wall where the hatch is, I was planning to install those "push-to-open" fittings.

But... should I install some kind of moisture barrier (plastic or other) behind the panels I put up? I assume there is something like that in the wall now - it should probably be between the panels and the insulation.

Anyone knowledgeable?

 

[sanne78]

no plastic..!! there is probably some solution for that in the existing wall..
however, do not build it too thick.. if there is plastic, it should be at most 1/3 of the wall's thickness..

if the wall that is there today is 20cm thick, you can use 95mm studs, no more.

 

[Prosit]

no plastic..!! there probably is a solution in the existing wall.. however, don’t make it too thick.. if there is plastic, it should be no more than 1/3 of the wall’s thickness..

if the wall that is there today is 20cm thick, then you can use 95mm studs, no more.

Oh, so if I, as I planned, put up studs that are 5-7 cm or so and then insulate the space between the old wall and the new panels, do I not need to install an additional vapor barrier (should I?)?

Can’t moisture get into my new insulation then?

Or maybe it becomes a risk if I put up more plastic (it’s not good to have two layers that stop moisture I guess - risk of moisture being trapped in between?)?

T