Double drywall ceiling, which drywall for the first layer? Without recessed edge?

[Tegelväggen]

Hello!

I'm working on a basement project and going to install drywall on the ceiling now.

To get the best possible soundproofing, I'm planning to use double drywall (to prevent footstep noise from going down into the bedroom in the basement and to prevent laundry room noise from going up to the bedroom above).

I will attach it to both the frame structure and the existing wood ceiling.

1. For layer one, do I buy any special drywall without recessed edges? I think it would be unnecessarily uneven if I screw the next layer right over such a recess.
   
2. Do I have to/should I use wet room glue/paper tape the joints on layer one? I've never learned how to tape paper strips.
   
3. Layer two. Does it need to be attached to the wood, or are 20 screws/m² in the drywall above enough? Where there is a wood ceiling, this is not a problem, but where there is only a floor joist, it might become a bit trickier to hit a stud.
   
4. Drywall for layer two: I haven't decided yet how to handle layer two, but I'm considering boards that are recessed all around or beveled. The ceiling height is just over 2m and the windows are almost up to the ceiling, so there will be lots of grazing light at eye level. Any ideas?

P.S. I’m planning to secure the existing plank and tongue-and-groove ceiling (t=25mm) with chipboard screws just to be safe before the drywall. P.S.

 

[Stefan1972]

you don't need any special plaster for that, just offset the joints on the next layer instead.

 

[eriobe]

Hello!

1. How do I handle the first layer, do I buy any special gypsum boards without recessed edges? I think it might get a bit unnecessarily uneven if you screw the next layer directly over such a recess.
   Use any boards. There won't be much difference, stagger the seams, or place the boards in different directions.
2. Do I need to/will I benefit from wet room glue/paper tape the seams on the first layer? I've never learned to spackle paper tape.
   No. You don't need to spackle. However, if you're very concerned about noise, you might possibly seal between the boards in the first layer. Uncertain if it makes much of a difference.
3. Second layer. Does it need to be attached to wood, or are 20 screws/m² in the gypsum board above enough? Where there is a wooden ceiling, this isn't a problem, but where there is only a floor joist, it could become a bit trickier to hit a beam.
   You must get the screws to sit in a beam. Use screws long enough to go through both boards. If it's tricky to hit a beam, you'll need to draw. Take the opportunity to make small pencil marks on the wall when you see the beams. When you then have the boards up, you can draw lines on the ceiling between your reference lines.
4. Gypsum for the second layer: I haven't decided how to handle the second layer yet, but I'm considering boards that are recessed all around or beveled. The ceiling height is just over 2m and the windows are almost up to the ceiling, so there will be a lot of grazing light at eye level. Ideas?
   If you use beveled boards, you don't need to spackle. Otherwise, you'll have to spackle, tape, and work hard to make it smooth.

 

[ramafred]

For layer 2, you can use a drywall screw, for example from Gunnebo. This layer should also be glued. Mounting adhesive should work well since the drywall screw will hold sufficiently until it has cured.

If you want better acoustics, you can use a soft sealant on the drywall joints. Maybe overkill, but buy something like Byggmax latex or similar, and it won't be much more expensive.

Best regards,
Freddan

 

[Jörgen Ö]

Doesn't it get extremely unnecessarily heavy with two layers of plasterboard?
Isn't it better to try to incorporate some form of soundproofing material above plasterboard layer 1?

 

[Tegelväggen]

Yes, weight is indeed a factor, 50m² and two layers weigh about 1 ton. Is there anything else that dampens with less weight? It's just one of the rooms, it's a frame structure that should be insulated.

Gypsum screws from Gunnebo: Is it a special screw? And do you only need to glue if you are not screwing into the underlying structure?

 

[Stefan1972]

First, one might ask if it is noisy today? It might be silly to paint a scenario that might not be accurate. Even if a little sound comes from downstairs, it should be manageable. Washing machines rarely run when someone is about to sleep, etc.

 

[ramafred]

Yes, the weight is indeed a factor, 50m² and two layers weigh about 1 ton. Is there anything else that dampens with less weight? It's only one of the rooms that is a framework structure that needs insulation.

Gipsskurv from Gunnebo: Is it a special screw? and do you only need to glue if you're not screwing into the underlying structure?

Gypsum is a very good material for soundproofing and it doesn't add much bulk. An alternative is to partially insulate the ceiling and leave a layer with an air gap. However, it quickly adds up to centimeters.

http://www.gunnebofastening.se/produkt/?product_id=74&family_slug=skruv

The idea with the screw is that you won't have to search for a framework, which is why glue is also required since gypsum itself doesn't hold very much. Some craftsmen skip the glue, but in a ceiling, I wouldn't take the chance.

 

[Tegelväggen]

Don't know how it is today actually, it wasn't living space before. You can hear quite a lot through it. The only downside of double plasterboard is the weight. It doesn't cost much and the work effort before plastering, painting, and furnishing isn’t that big now.

I don't think the floor beams are over-dimensioned as it already flexes a bit today, but the question is what 1-200kg of plasterboard does in terms of difference for a room.

I have no idea unfortunately. I thought double plasterboard was standard between floors.

 

[ramafred]

@justusandersson might be able to chime in with some thoughts?

 

[nino]

I screwed up double plasterboard and ceiling, braced down and placed sparse on cc300
I sealed the plasterboard with latex in the joints and against the walls.

I also placed a 45 insulation between the existing ceiling and the new one.

I staggered the joints, a little difficult to find screws for 3x12mm boards.

 

[Nils82]

Stagger the joints, both long and short joints. Fully screw both layers, make sure you have something stable to screw into. If you want to invest in a soft sealant, apply it on layer 1.

Good luck.

 

[Tegelväggen]

Regarding the soft joint, do you set the boards with a small gap in layer 1? like a 5-15mm gap? so you can fit the joint.

50 gypsum boards will be purchased this weekend. It's going to be quite a haul down to the basement.

 

[Nils82]

Regarding the soft joint, should you place the panels with a bit of spacing in layer 1? Like a 5-15mm gap? So you can get the joint in.

50 drywall panels will be bought this weekend. It will be quite a haul down to the basement.

No, you seal around. That is, in the wall/ceiling angle and any penetrations.

 

[nino]

I also pulled at the seams, you never know which way the air/sound takes and if you do everything you can then you have done it... if you skip a step and it's still noisy you start to wonder...