[ln1234]

I'm placing an order for some sound proofing materials, and I wanted to know what kind of Acoustic sealant the online sound proofing websites sell? This will be used to seal the 5mm gap around the ceiling after the installation of resilient bars and double sheet plasterboard.

Is it the same stuff as this?

Cheers

[Ted White]

That'll work. I'd also not leave the gap. The theoretic reasons for the gap are:

#1 To reduce conduction from the wall to the ceiling

#2 To provide a big gap that we can be sure gets sealed. Often a "backer rod" is suggested before the application of the sealant so you don't pump your walls full of sealant.

#3 To allow the decoupled ceiling to move as freely as possible, increasing flex. The goal is to minimize edge constraint.

In reality:

#1 In a theatre, both the ceiling and wall are being bombarded with the same vibration. Pretend the speaker in the room is a heater. The walls and ceiling are being equally heated to the same temperature. What good would a gap do?

#2 The room will effectively be sealed without a concerted effort to leave a 5mm gap. The finish plaster will also seal, as will paint. Some sealant after the final layer of plasterboard is of course a good idea.

#3 This free-floating ceiling concept has more merit with very small panels. On a large ceiling, there's very little edge constraint relative to the overall surface area of the ceiling. And let's not forget that any sealant will introduce edge constraint.

Additionally, if the ceiling plasterboard is butted right up to the wall plasterboard, installation is easier and you have mass in the intersection.

So from a practical standpoint there's no compelling reason to leave the gap. Having said that, as long as you take care to fill the potentially libelous 5mm gap, that's OK too.