Must (or should) wall have drywall for wet room behind wet room mat?

[widheg]

I am going to build interior walls for my future wet room. I plan to install OSB boards against my standing wall studs (CC=600 mm). Then plasterboards and finally a wet room mat. Must (or should) I use wet room plasterboards instead of regular plasterboards in my case (as I will still have my surface layer as a waterproof layer)?

Note 1) I have understood that the wall studs' CC distance does not need to be 450 mm in my case since I will not have a ceramic surface layer. Is that correct?

Thanks for the motivated answers!

 

[tergo]

Note 1) I have understood that the wall stud's CC-distance does not need to be 450 mm in my case since I am not going to have a ceramic surface. Is that correct?

YES

ordinary plasterboards are fine

if you use both OSB+plaster, it's also fine for tiles

 

[BirgitS]

It is approved to use cardboard-covered gypsum board in wet zone 1 and 2 under vinyl flooring. See here: https://www.gvk.se/branschregler/vagg/skivmaterial
Unless the manufacturers of the vinyl flooring and the adhesive state otherwise in their instructions.

 

[MrJay]

As far as I know and have built, 15mm plywood is required in bathrooms and not OSB...

 

[Paul-Staffanstorp]

Nothing is required behind the plasterboard and ordinary plasterboard is now approved...

BUT...

If you want to be able to make approved fixings later, I would have swapped OSB for 15mm plywood as it is virtually impossible to know in advance where you need to insert noggins, so it's better to spend a little extra money on plywood and be on the safe side later.

 

[widheg]

Nothing is required behind the drywall and regular drywall is now approved...

BUT...

If you want to be able to make approved fastenings later, I would have replaced OSB with 15mm plywood as it is nearly impossible to know in advance where you need to install noggings, so it is better to spend a little extra on plywood and be on the safe side later.

Thanks! So plywood is better to fasten into compared to OSB (if they were the same thickness)?

 

[Paul-Staffanstorp]

They are not as thick because OSB is only 11mm, and according to BBV, not approved for fastenings, which 15mm plywood is. So, you must use battens everywhere fastenings are to be made.

Also, plywood is generally much better than OSB, even when talking about the same thickness, as OSB’s density is much lower. If you screw into an OSB, remove the screw, and try to screw into the same hole, the screw won't hold again. If you screw too far and tighten the screw too much in an OSB, it ends up with the screw just turning around, creating a sort of hole.

In an average-sized bathroom, we are talking about roughly 1500-2000kr more expensive with 15mm plywood, so it's quite negligible to get it 100% approved.

 

[widheg]

They are not as thick because OSB is only 11mm and according to BBV not approved for fixings which 15mm plywood is, so you would have to install battens everywhere fixings are needed.
Then plywood is generally much better than OSB even when discussing the same thickness as the density in OSB is much lower.
If you screw into an OSB, remove the screw and try to screw into the same hole, the screw won't grip again.
If you screw too far and tighten the screw too hard in an OSB, it will end up with the screw just continuing to spin and you create a kind of hole.

In an average-sized bathroom, we're talking about 1500-2000kr more expensive with 15mm plywood, so it's quite negligible to get it 100% approved..

Thanks for the detailed answer!

 

[Tim Uddfors]

Thank you for the detailed response!

I would follow Säkervatten's wet room wall guidelines, follow the link.

fohttps://sakervatten.se/wp-content/uploads/2024/02/folder-vatrumsvagg-2012.pdflder-vatrumsvagg-2012.pdf (sakervatten.se)

 

[Paul-Staffanstorp]

I would follow Säkervatten's wet room wall, follow the link.

fo[link] (sakervatten.se)

What is the difference from what I explained... 🤔

Good with the link though, it makes it easier for TS to build correctly.

 

[Förvaltare]

The flooring installer I hired firmly advised against using wet room gypsum boards, due to poor adhesion for the glue. Good luck.