Author Topic: Is decoupling a ceiling better done with a new lumber drip ceiling vs channel?  (Read 4996 times)

srj19

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Hello,

I have a small bath room that would be less than 5 feet to span with a new lumber drop ceiling. What is the consensus for small spaces like this? It would seem a new lumber drop ceiling would even exceed the decoupling of a directly connected channel and clip system since there is no connection to any structure except through the wall studs.

An I on the right track? Of course I'll be using some roxul in the cavity and probably two 1/2 green glue layers on top of the new framing.

what do you guys things?

Thanks,

Scott

Randy S

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The flanking noise can still enter your new ceiling from the walls that are still connected to the subfloor above.. So I would say that clip and channel would be a better option.
Randy Sieg

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888-942-7723
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srj19

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Ok that's interesting. I thought that because the direct joist connection was even better than with channel....(none!) the flannking sounds that still would be present (as they would be with channel) but the direct overhead would be all but eliminated due to no direct joist connection.

Are you saying that the flanking will be more evident if it goes from:
 The above floor & subfloor > Joists > Top Plate > lower room wall Studs > New Drop Ceiling Perimiter > New drop ceiling 2X4 joists > green glue and then out into the room vs. clips and channel attached directly to the joists?


Randy S

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Remember that impact noise is the hardest to reduce along with low frequency. When you do a clip and channel float the perimeter is held off of the walls by 1/4" and the gap is filled with caulking and the clips are a neoprene clip with a low rate of vibration. What would remain to address would be the airborne sound with in the cavity.

keep in mind the speed of sound through a 2x4 is 12x times faster than airborne sound.

both methods will show a value of reduction.
Randy Sieg

Super Soundproofing Co
www.soundproofing.org
888-942-7723
Ph. 760-752-3030
Fax.760-752-3040

srj19

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Hello,

Can anybody help me understand why a decoupled wall with staggered studs is effective for stopping sound through walls but not when using the same theory horizontally? (as in staggered joists tied to the studs of the perimeter walls and slightly lower (and fully disconnected from the original ceiling joists)?

 A ceiling suspended with clips and channel has probably 40 contact points directly tied to the joists (albeit with neoprene rubber boots to absorb some impact) and that is still better than a staggered/decoupled joist ceiling as I described above?

I'd put roxul in the cavities, double rock with green glue between, and caulking the perimeter of the ceiling with soundproof caulk. I might even put some neoprene rubber insulating material between new ceiling joists and the wall studs to further absorb flanking.

Flanking and sound in general would seem to be less in the room below because in most rooms the walls stack from floor to floor and impact could not occur directly above the contact points because directly above the contact points is a stud wall above. So footfall above occurs out in the field somewhere on the 2nd floor and must travel horizontally through the joists and sub-flooring over to the walls, where now it must travel down into the top plate, down into the wall studs of the floor below and into the new sub ceiling joists, through rock layer one, green glue and rock layer 2 in order to eminate out into the room below.

Help me out, why isn't this a cheaper and just as effective way to accomplish the clip and channel level of decoupling and soundproofing? I used clip and channel to do my living room, and in a older house that has had settling or normal low points in the center of a span....I had a ton of leveling and point to point work to get it all right. Running a new joist from wall stud to wall stud and leveling it seems a whole lot easier.

Scott

srj19

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I should mention I have balloon framing and so the original studs themselves are tied to the outside walls, which I believe is a bit different than modern framing methods

jhbrandt

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Scott,

I have the full ir761 document (STL research) on my publications page. You can download and review. You will see that a fully decoupled partition such as resilient channel out-performs the staggered stud configuration.

Your STL requirement was not mentioned. (Sound Transmission Loss) Do you have a decibel spec you are trying to meet? and at what frequency? The devil is in the details.

When we do an 'isolation build', many factors come into play; Budget, STL & frequency range, physical limitations, time, etc., etc., etc. These determine whether we will build a single partition wall with high mass, a partially decoupled MSM partition (staggered-stud), clips or res-channel, or (the best) completely independent isolated partition. - With completely isolated partitions, we have even used spring hangers for the isolated ceilings and not built the iso ceilings on top of the iso walls. - Many ways to skin a cat. ;)

Cheers,
John

 

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