Install a drywall partition for the bathroom

Hello everyone,
I want to partition off a bathroom in a room. I have marked the wall lines in red on the picture.
The wall will be 3.40m high.
For the cladding, I want to use 15mm OSB boards and above that 12.5mm gypsum plasterboard.
I want to realize it with metal UW and CW profiles.

Can you tell me what minimum width the UW and CW profiles should have?

My further questions are:
- Do the OSB boards have to be installed staggered?
- Do the joints of the OSB boards have to be filled and sanded?
- I have read that a few millimeters of space should be left between the boards and the wall / floor / ceiling. How can I seal this gap against sound?

Thanks in advance

As a rule, you use 50 mm.

I would go for 75 mm, that way the wall will be 13 cm thick in the end. Insulation in between, which will also be a bit thicker then. You can also fit a proper door frame (14 cm) in there, which looks better visually.

Make sure to install the OSB boards staggered with tongue and groove. No cross joints. You don’t need to fill in anything, there will be drywall over it anyway. For safety, I would apply a vapor barrier under the boards. The OSB boards should act as a barrier, but because of the wet room, I would play it safe and use a foil there as well. At least on the bathroom side. Knauf Insulation is well suited here.

It’s best to fill the gap to the wall with silicone. I always use body filler adhesive, it doesn’t break and stays dimensionally stable, etc. Sikaflex or something similar is appropriate here.

thank you for the answer, that already helps me a lot.

I have two more questions:

- the current floor in the bathroom is one layer lower than outside the square. Outside the square, there will be another layer of laminate (which will then be the final floor). In the bathroom, presumably screed? and then tiles. My question: does it make sense to start the wall construction now and place the CU profiles on the current subfloor?

- how do I best cut the OSB boards? Handsaw, electric hand circular saw, or jigsaw?

For long straight cuts, use a circular saw; for complicated cutouts, a jigsaw. I wouldn't use a handsaw for panels (more likely for a strip/ a beam if no miter saw is available).

A circular saw is rather not suitable. Sheets can be cut straight with a handheld circular saw and an appropriate guide.

You dummy, that’s what was meant.
If the questioner talks about a [Handkreissäge] and I shorten it to [Kreissäge], I’m not suddenly referring to a [Tischkreissäge].