ᐅ Interior Wall (Vapor Barrier) – Sheathing / Cladding

Hello everyone,

I have a question about the wall sheathing. In the scope of work description from the builder we chose, it says:

Interior walls: 18 mm (¾ inch) fire-resistant gypsum board, unjointed 100 mm (4 inches) timber frame 50 mm (2 inches) thermal and sound insulation within the frame

Is that sufficient, or should there be two layers of fire-resistant gypsum board instead?
What exactly does that mean?

Am I wrong to assume that there is also a gypsum board on the other side of the wall?

Best regards and many thanks,

Hello again,

Correction: I totally got it wrong just now – thank goodness the house isn’t built yet.

The exterior wall is constructed as follows: 18mm (0.7 inch) drywall with a vapor barrier. The assembly is vapor-permeable. According to the building regulations, it’s considered safe to attach anchors and screws directly to the drywall. However, I have some doubts about this.
An installation cavity would cost around 7,000.

I’m currently debating whether to add it or not. I don’t really need it everywhere. The kitchen is the first place that comes to mind.

What do the experts recommend? Or are there alternative solutions?

Hello,
if the vapor barrier of the exterior walls is penetrated or damaged at any point, moisture from the indoor air can enter the wall insulation, potentially condense there, and damage the insulation. This can lead to mold and other issues.
Possible penetrations in the exterior wall include:

* Electrical outlets
* Conduits from inside to outside, e.g., onto a terrace
* Heating pipes for radiators
* Water supply pipes

If the drywall serves as the vapor barrier—meaning there is no dedicated vapor barrier film—then the above points either do not apply or require complex sealing to ensure connection to the vapor barrier.
Have the proof of the walls’ moisture protection shown to you. When calculating the U-value for the wall assembly, it can be determined whether the component is protected against moisture ingress.

Otherwise, I recommend involving an independent engineer or energy consultant, whom you hire, to advise you.

Best regards

Hi,

NorbertKoch schrieb:

Should the drywall be the vapor barrier,

Drywall cannot serve as a vapor barrier.........

Regards