Drywall with black plastic on the back

[Eraze]

Hello

We had to open up the wall to run electricity and saw that there were plasterboards with a black backside, like plastic.


The house was built in '76.
When I checked different sources, if I understood correctly, after insulation there should be a vapor barrier and then plaster?
Is this instead of a vapor barrier because there isn't one.

When I spoke to a carpenter, he said there isn't a vapor barrier on the insulation.

So how should we proceed here when putting up plaster again?

 

[tergo]

it's black

Is it instead of a vapor barrier because there isn't one.

Yes
you should put age-resistant plastic when plastering

 

[Eraze]

det svart

Yes
you need to put age-resistant plastic when plastering

Shouldn't it be certain centimeters to all holes, like 30 cm above. Because it. Doesn't work. Or is it enough to tuck in a bit under the old plaster?

 

[tergo]

Yes if it is spliced on the beam or if it is possible to tape the splice https://www.byggmax.se/skarvtejp-åldersbeständig-p21600

 

[Eraze]

Yes, if it is jointed on the stud or if it is possible to tape the joint [link]

Don't really know how to tape on the back. Thinking... They have put plasterboards with plastic on the back. So it's attached to the plasterboard. Therefore, there is no plastic in the joint between the plasterboards. So maybe it's enough to tape new plaster and apply it?

 

[Anders243]

Yes, if it is joined on the beam or if it can be taped at the seam [link]

No! No! This blue tape is totally worthless. I've encountered several rolls that barely stick to new plastic, let alone other surfaces. However, their green tape in the same section is excellent. For 120-130 kr it is worth the price.

Edit: this one is much better.
https://www.byggmax.se/tätningstejp-åldersbeständig-sp-p21601

 

[Eraze]

No! No! This blue tape is totally worthless. I've encountered several rolls that barely stick to new plastic, let alone other surfaces. However, their green tape in the same section is excellent. For 120-130 kr, it's good value.

Edit: this one is much better.
[link]

Thanks for the tip
But how should I tape this? On the back of the gypsum board or on the studs and just pull down (should saw the opening straighter). There will be a seam either way.

 

[Anders243]

I figured that you could tape a piece of vapor barrier plastic and then attach a board in the usual way. It's easiest if you have access to the studs, but otherwise, you can screw a piece of plywood to the existing drywall and let it protrude into the hole to attach the new piece and plastic to it.