ᐅ Triple-layer drywall installation on individual interior walls

Created on: 26 Aug 2023 23:40
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RobertHell
Hello,

with most timber frame house suppliers, the wall construction is usually designed so that on the living space side (after the insulation) a 15mm OSB board (about 0.6 inches) is installed, followed by a 12.5mm plasterboard (about 0.5 inches).

For soundproofing reasons and to securely fix cabinets or similar items, we are considering installing an additional plasterboard layer on certain walls as a DIY project.

I have read in various forum posts that this is possible and can be quite effective. Do you also think this makes sense for our purpose?

Is the following procedure correct?
Assuming the first plasterboard layer has been properly jointed:
1st step: screw on the second plasterboard layer with drywall screws, staggered
2nd step: apply primer into the joint (where the plasterboards meet)
3rd step: fill the joint and screw heads with joint compound
4th step: sand the wall
5th step: prime the entire plasterboard surface
6th step: paint

Should I inject elastic acrylic sealant into the joint to prevent cracks in the plaster later on?

Another option suggested by the house builder would be to use 22mm OSB boards (about 0.9 inches) instead of 15mm, and keep just one layer of plasterboard.
What do you think about this proposal?

Can anyone tell me how much a 15mm OSB board, a 22mm OSB board, and a 12.5mm plasterboard reduce sound transmission?

Thank you for your answers
Robert
i_b_n_a_n28 Aug 2023 20:17
You can safely hang two elephants on 15mm (0.6 inch) OSB board (provided you have the appropriate screws) and even have an import permit for elephants.

For soundproofing, you need mass and/or preferably a secondary wall that is decoupled from the main wall (you were mainly concerned about structure-borne noise, right?). However, this requires space and a sufficiently large budget.
11ant28 Aug 2023 22:52
i_b_n_a_n schrieb:

You can safely hang two elephants on 15mm OSB (provided you get the right screws) and have an import permit for elephants.
I am one of a kind, but I don’t need to be imported into Germany anymore ;-)
https://www.instagram.com/11antgmxde/
https://www.linkedin.com/company/bauen-jetzt/
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RobertHell
1 Sep 2023 09:05
Okay, then I don’t see any reason to switch from 15mm OSB to 22mm OSB, unless there is a reason I might have missed? It certainly shouldn’t cost that much more.

One more question regarding the second layer of drywall over the first drywall layer:
Do I really need to apply joint tape at the seams? From my understanding, cracks are more likely to occur between the OSB and the first drywall layer due to the different materials and their varying expansion.
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Simon-189
1 Sep 2023 11:04
RobertHell schrieb:

One more question about applying a second layer of drywall over the first drywall wall:
Do I really need to embed mesh tape at the joints? As I understand it, the cracks are more likely caused by the OSB behind the first drywall, since the different materials expand differently.

That is probably true, that the movement mainly occurs at the material transition.
However, keep in mind that the second layer will be your visible surface, since it will apparently be primed and painted directly.
I would consider it too risky to avoid cracks altogether. In my opinion, using a roll of mesh tape there is definitely worth it.
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HarvSpec
1 Sep 2023 11:25
If you want a clean result, I would definitely embed mesh tape, then apply a full skim coat and sand it down.

Personally, considering the concerns, I would lean more toward a construction-side solution during the wall build rather than a "DIY fix" afterward, especially when the effect is uncertain. I tend to prefer doing it properly from the start, but everyone has their own approach.