ᐅ Install a drywall partition for the bathroom

Hello everyone,
I want to section off a bathroom in a room. I have marked the wall lines in red in the picture.
The wall will be 3.40m (11 ft 2 in) high.
For the cladding, I plan to use 15mm (5/8 inch) OSB boards with 12.5mm (1/2 inch) drywall panels on top.
I want to build it with metal UW and CW profiles.

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

My other questions are:
- Should the OSB boards be installed with staggered joints?
- Do the joints of the OSB boards need to be filled and sanded?
- I have read that you should leave a few millimeters of gap between the boards and the wall/floor/ceiling. How can I seal this gap to prevent sound transmission?

Thank you in advance

Usually, you use 50 mm (2 inches).

I would go for 75 mm (3 inches), which makes the wall about 13 cm (5 inches) thick in the end. Insulation will then also be a bit thicker. You can also fit a proper door frame (14 cm / 5.5 inches) in there, which looks better visually.

Make sure to install the OSB boards with a staggered, tongue-and-groove pattern. Avoid cross joints. No need to fill or skim; drywall will be installed on top anyway. For safety, I would apply a vapor barrier under the boards. Although OSB boards are meant to be a barrier, due to the wet room conditions, I’d recommend using a foil for extra protection, at least on the bathroom side. Knauf Insulation works well here.

Fill the gap between the wall and the boards with silicone. I always use body filler adhesive, which doesn’t break down and remains stable over time. Sikaflex or a similar product is suitable for this.

Thank you for the response; it already helps me a lot.

I have two more questions:

- The current bathroom floor is one layer lower than the area outside the square. Outside the square, there will be a layer of laminate flooring (which will be the final floor). In the bathroom, I assume there will be a screed layer? and then tiles. My question: does it make sense to start the wall construction now and fix the metal stud profiles (CU profiles) to the current subfloor?

- What is the best way to cut the OSB boards? Hand saw, electric circular saw, or jigsaw?

For long straight cuts, use a circular saw; for complex cutouts, use a jigsaw. I wouldn’t use a handsaw for panels (more suitable for a strip or a beam if no miter saw is available).

A circular saw is generally not suitable. You can cut boards straight using a handheld circular saw and an appropriate guide fence.

You blockhead, that’s exactly what I meant.
If the asker writes about a circular hand saw and I shorten it to circular saw, I’m not suddenly referring to a table saw.