Ceiling, 3 layers of drywall, studs?

[Studion]

Hello,

I am going to install a free-standing ceiling on interior walls. Gypsum on top.
What dimensions and strength do I need for the ceiling joists with three layers of 13 mm gypsum?
It will be laid on partially sloped walls, so the span is between 4.2 to 5 meters on six to seven joists and then about 4.20 meters on about 7 joists. I am thinking cc600.

No weight on top of the ceiling afterward, so the only thing to be supported is the gypsum.

Hope you understand what I mean with my rambling.

 

[injonil]

Wood bends easily at spans of 5m due to its own weight. We can only guess, but I would guess that 45x120 is suitable. Maybe even 45x145.

 

[Matti_75]

Plasterboard in the ceiling requires c/c400mm, then you can place an attachment point in the middle so you don't need such thick joists.

 

[Studion]

Plasterboard in the ceiling requires c/c400mm, then you can place a fixing point in the middle so you don't need such thick beams.

Thank you for your answers. I don't quite understand. Why is c/c400 required and what do you mean by fixing point?

 

[injonil]

Gypsum sags at higher cc than 400mm in the ceiling. However, I do think it will still be fine since you plan to lay 3 layers.

 

[Björn Melander]

I assume it's for your studio construction (thinking about your other thread), and then it’s good if you work with c/c 600 mm to achieve the best possible sound reduction. Imagine the gypsum functioning as a flexible membrane. I would probably choose 45 x 195 mm with c/c 600 mm, alternatively a smaller dimension with screw-glued plywood strips on the side/sides.

Remember that the ceiling should then withstand the load of acoustic treatment in the ceiling. If you're building a control room/listening room, you shouldn't have angled walls. However, if it's a recording room, it matters less.

 

[Studion]

I assume it's for your studio construction (thinking about your other thread), and then it's good if you use c/c 600 mm to achieve the best possible sound reduction. Imagine the drywall functioning as a flexible membrane. I would probably choose 45 x 195 mm with c/c 600 mm, alternatively a thinner dimension with screwed-glued plywood strips on the side/sides.

Remember that the ceiling will then need to handle the load of acoustic treatment. If you're building a control room/listening room, you shouldn't have angled walls. However, if it's a recording room, it matters less.

That's correct, Björn. Wanted to keep it in different threads due to different areas, maybe a bit overkill.
Thanks for the answer!

The load from the acoustic material will end up on the lower ceiling if I build two ceilings resting on their respective walls. The top ceiling should "only" need to handle three layers of drywall. Or am I thinking silly?

 

[Björn Melander]

That's correct, Björn. Wanted to keep it in different threads due to different areas, perhaps a bit overkill.
Thanks for the answer!

The load of acoustic material will end up on the lower ceiling if I build two ceilings resting on each wall. The top ceiling should "only" handle three layers of drywall. Or am I thinking weirdly?

Aha, now I understand. You are thinking correctly.

 

[Studion]

How nice

But do you still recommend 45x195 studs in that case, or?
And what strength should one aim for? I'm thinking of C14, C18, C24 etc.

 

[Björn Melander]

There are surely designers here who can do this better than I can. I usually look up tables and quick references for these types of loads (kg/m2). However, I'm not in the office right now. From practical experience, you will have both suspenders and a belt if you build with 45x195 and C-24. C-14 will probably suffice just fine, or alternatively 45x170 C-24.

 

[Studion]

I counted with 45x170 C24, so maybe I wasn't that far from the truth then It would be great if more people have concrete thoughts and tips, I am extremely grateful!

 

[Studion]

Björn, do you have any tips or links to good tables where I can find more info on the weights different studs can support (also for walls)? I read a lot in Gyproc's handbook, among others, but sometimes a bit more concrete guidance is needed.

 

[vectrex]

If you're going to have panels on the walls, you don't need a table. In theory, you could build them from 45x45 studs. However, I think it's unwise to use anything less than 45x95, as the price difference is minimal.

Assuming this is for the studio you mentioned in another thread? So, no snow or wind load, just a roof that needs to support its own weight.

I believe 45x170 C24 is the right way to go; I wouldn't use anything weaker. Even though it's just for a "ceiling," walking on it will be quite wobbly with a 5-meter span.

 

[Studion]

Thanks! However, the roofs need to be self-supporting and rest on the walls, so it's more than just three layers of drywall that need to be supported by the walls. Then there's going to be some items hung to regulate the acoustics, etc., adding a bit more weight.

My thought is 45x70 or 45x90 studs in the walls at cc600 (plus noggins at cc600). But when it comes to the strength of wall studs, is it also C24 that's applicable...? I understand the overall principles, but I would like to get into a bit more of the details.

 

[vectrex]

Thanks! However, the roofs will be self-supporting/free-standing and rest on the walls, so it's more than just three layers of plasterboard that will be supported by the walls. Then a number of items will be hung to regulate the acoustics, for example, and that adds a bit more weight.

My thought is 45x70 or 45x90 studs in the walls at cc600 (plus blocking at cc600). But regarding the strength of wall studs, is it C24 that applies there as well...? I understand the overall principles, but I would like to get a bit more into the details.

Yes, I understood the construction. Still, I maintain that 45x45 would work but it feels weak. If you go with 45x70 or 45x95, it's easier to build with 45x95. C14 is always sufficient for the walls. Skip the blocking, it's not needed considering all the boards, better to go up to 45x95 in that case!