Furring channel on ceiling?

We've built a free-standing 12' x 9' room-in-room on basement slab. Worst noise is low frequency footfalls from above. Ceiling framing is 18 gauge sistered pairs of steel 2"x4" (screwed back to back) 24" OC on 9' span. We're going to use 3 layers of 5/8" sheetrock under the joists and 3 layers of 2" Owens Corning 703 in and above joists. We were going to screw sheetrock directly into joists, to achieve a stiff mass. Then we hired a sheetrock sub because we're exhausted, and he wants to attach 3/4 " deep U-channel 16" OC perpendicular to joists and hang rock on that. (Ceiling height is an issue, too.) Questions: 1. Will the channel help or hurt preventing low frequency transmission from above? 2. Is hanging this much rock on channels safe? Sorry to ask since RC has been discussed so much here. I have to say I'm still too confused to apply what I've read and reread to this case. Thanks very much.

Hi all, this is my 4th post, never a reply. I've learned so much from this forum, and really appreciate all of the work people put into it. I don't think I need a sketch/photo for this, or TMI, but let me know. The channel would actually make it easier for me since I can use it to help hold the insulation in place before the rockers start. I'm concerned that they want to do it because it's easier for them, and the last thing I want to do is worsen the low frequency isolation. Would love a quick answer. Thanks.

ok, last try. I decided to tell the rockers not to use the channel. Reasoning: The 3 sheets of 5/8" sheetrock and relatively rigid joists of the new ceiling form a good mass. Since the new ceiling and walls are completely independant of the old ceiling and walls, it would be better to have a solid immoveable mass. Still appreciate confirmation or opposing views. Thanks.

Very short on time here... Family emergency going on. The critical question is... What are these new ceiling joists attached to? Are they attached directly and firmly to the floor joists from the living space above? If so, that's not going to improve your footfall problem very much, if at all. You have to decouple upstairs from downstairs. The best way to do this is to have separate inner leaf framing attached to the basement floor, and then firmly attach new joists to the top plates of the new walls, having no firm connections between the new room and the existing structure except for the floor slab. You only described the room's width and length, but not its height, so at this point we don't even know if what I have proposed is practical or not. Buy Rod's book -- I would actually highly recommend buying it and being completely certain of everything you need to do before construction begins again. You are at a critical point in your build where mistakes are virtually unrecoverable. You'd be wise not to paint yourself into a corner, as one bad move (or a conspiracy of many) could lead to a disasterous result. --Keith :mrgreen:

Thanks so much for your reply, and sorry about the family emergency. We own and have studied Rod's book. We have already finished the entire inner framing EXACTLY as you described, with no connection whatsoever to exisiting walls, ceiling, joists etc. The first layer of new ceiling sheetrock will be 8" below the old existing ceiling, most of which space will be filled with 703 (3 layers). Counting 3 layers of sheetrock and 2" of insulation inside, that leaves us 6'8" of height in the new structure. The only question regarding the ceiling is whether to use the furring channel the rockers want to use to attach the ceiling's 3 layers of sheetrock or not. Thanks again.

Install directly to the ceiling joist - you gain nothing what so ever )from an isolation point of view) using channel - and I see no reason to add the extra weight. Rod

Great, thanks very very much for the response. Roma Baran http://www.baranstoll.com