i need to soundproof my ceiling i was thinking of using 2*2 studs inch away from the ceiling stuff it with rockwool then use 1 layer of 12m plasterboard then 1 layer of 9.5m plasterboard do you think this will work

[Jimbo73]

Think that might be too heavy? What will stop it from sagging in the middle?

[Gary Lightfoot]

What would work better, is to remove the existing ceiling, install new timbers that are the same dimension as the existing ones (or the same as those for the bedroom ceiling which would also be the floor for the loft - say 4 x 2 instead of 6 x 2 for example) so that they fit in between (but not touching) the existing timbers. This would give you the strength to hold up the new plasterboard without sagging and be more effective for soundproofing. It also means you don't lower the ceiling any more than you have to as only 2ins of the new beams has to be protruding from the existing beams.

Finish with Rockwool insulation and two layers of 1/2" plasterboard or one 1/2" and another 5/8ths". Seal all edges with silican sealant or similar to ensure there are no air gaps for sound to travel through. Fit a thick rubber underlay material upstairs before laying the carpet. It might help to seall all the gaps in the upstairs floorboards as well as the edges by the skirting while you have the carpet up.

Gary.

There are of course commercial systems made for sound insulation when refurbishing. Important features for what you do:

1. airtight seal from floor above
2. mechanically isolate new ceiling from floor above (somebody makes sort of springy hangers to support the ceiling without transmitting vibration).
3. mass (more mass is better).