Studio Construction in France

[gullfo]

GWB = gypsum wall board = drywall

[faucon2001]

I will start the sound proofing next week according to the previous plan named "Proposal".
Before starting to build it, I have done a simulation of first reflexion point to anticipate the extra weight the walls and ceiling will have to support. Regarding the walls, I am not really concerned as the rock wool panels with start on the floor up to the ceiling.

But regarding the ceiling and the cloud, I am more concern by the extra weight.
I plan to build a 2x1 m cloud with a back of MDF 6mm and 80 mm of rock wool @70kg/m3, with a weight around 20 Kg. According to the drawing, the cloud will be angled to reject the sound to the back of the room.

Is the cloud structure OK? Do I need a thicker MDF board, adding more weight to the cloud?
Is 70 Kg/m3 a correct density for the rock wool?

The ceiling will be screwed on a metal frame spaced every 60 cm hanged to the joist according to the drawing.
I have read technical documentation for dry wall resistance : for a single dry wall sheet, it can support up to 5Kg per screw. There is no data for a double dry wall sheet.
Do you thing such a ceiling is able to withstand 20Kg of extra weight with 6 screws (3.3 kg per screw)?
I have the possibility to add an extra frame ( metal or wood?) before putting the dry wall in order to screw the cloud to it instead of the dry wall. Do you think it will be enough or should I consider hanging the cloud directly to the joist?

[gullfo]

best bet - hang the cloud using hooks and chain so you can angle it and adjust the height.

[faucon2001]

For sure I will use adjustable hangers for the cloud.
My main concerns are the weight resistance of the ceiling and the specification to build the clouds (wood thickness and rock wool density).

I have done some search on ceiling resistance specifications, and found that the standard ceiling hangers have a recommended maximum resistance of 55 Kg/m2. As the ceiling I plan to build with insulation weight around 42 kg/m2 and the clouds 10 Kg/m2, I should still be under the 55kg/m2 limit, but with a small margin.

Based on your experience, would you recommend instead to hang the cloud directly to the joist and not to the ceiling?

[gullfo]

yes the hooks should go into the joists. however when the joists don't line up as expected, some 2x4 or even a sheet of 20mm / 3/4" plywood to span the joists and secured with lag screws and then the hooks go into the 2x4 or plywood. this way you're able to get the right distribution across all the hooks and the additional stiffness created by the plywood and / or 2x4 can help with overall weight distribution.