# Sound Attenuation



## builder49 (Feb 24, 2010)

I have to construct a fire rated wall assembly separating two rooms and would like to add sound attenuation at the same time. Has anyone had experience with "Green Glue" or other products used between layers of drywall? The wall assembly will be 2x stud wall with double layers of 5/8" drywall. Thanks, builder49


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## Sir Mixalot (Jan 6, 2008)

I've done a couple recording studios. 
If you can, install some hat channel horizontally on the 2x4's first. This will help tremendously in soundproofing.:thumbsup:


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## Rich D. (Oct 14, 2011)

On a open wall (no drywall) mount resilient channel horizontal to the studs. Screw this channel into the studs and make sure the channel is not touching the floor, top or bottom plates, and adjacent walls.

Now screw on a layer of homasote, it is very important to screw the homasote on in between the studs into the resilient channel. DO NOT screw it into the studs or plates, thats important. Seal all seams with an acoustic sealant.

Now do the same with your layers of rock. Again do not screw into studs or plates.

Ive never used green glue but ive heard good things about it. Its $$$


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## Sir Mixalot (Jan 6, 2008)




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## Rich D. (Oct 14, 2011)

Sir Mixalot said:


> I've done a couple recording studios.
> If you can, install some hat channel horizontally on the 2x4's first. This will help tremendously in soundproofing.:thumbsup:


Why do you use hat channel instead of resilient channel?? For me hat channel is almost 2 bucks more per 25ga 12' length compared to resilient channel, plus resilient channel works better. :thumbsup:


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## Henn Drywall (Dec 17, 2012)

They're screwing off their drywall with a cordless........


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## ohiohomedoctor (Dec 26, 2010)

Its all about the homasote..


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## Sir Mixalot (Jan 6, 2008)

Rich D. said:


> Why do you use hat channel instead of resilient channel?? For me hat channel is almost 2 bucks more per 25ga 12' length compared to resilient channel, plus resilient channel works better. :thumbsup:


There's a reason why RC is cheaper. :thumbsup:
Resilient Channel was originally brought to the mass market decades ago by USG (United States Gypsum). The product was trademarked as RC-1, and tested extensively at Riverbank Acoustic Laboratories. Today many installers, architects and material retailers refer to any channel with one “leg” as RC-1. It’s important to note that USG hasn’t dealt with the original resilient channel design for years and years. Since then, many manufacturers have made a “resilient channel” and informally referred to previous USG test data for acoustic performance. This is entirely misleading and quite unfortunate. Resilient channel available today has many profiles, mil thicknesses and performance characteristics, so it really not possible to simply predict how any given piece of “resilient channel” will perform. Additionally any 1 or 2 legged resilient channel is not specified by the Steel Stud Manufacturers Association (SSMA). So there are no standards for its construction or use.


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## ohiohomedoctor (Dec 26, 2010)

Nice explanation


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## Rich D. (Oct 14, 2011)

Sir Mixalot said:


> There's a reason why RC is cheaper. :thumbsup:
> Resilient Channel was originally brought to the mass market decades ago by USG (United States Gypsum). The product was trademarked as RC-1, and tested extensively at Riverbank Acoustic Laboratories. Today many installers, architects and material retailers refer to any channel with one “leg” as RC-1. It’s important to note that USG hasn’t dealt with the original resilient channel design for years and years. Since then, many manufacturers have made a “resilient channel” and informally referred to previous USG test data for acoustic performance. This is entirely misleading and quite unfortunate. Resilient channel available today has many profiles, mil thicknesses and performance characteristics, so it really not possible to simply predict how any given piece of “resilient channel” will perform. Additionally any 1 or 2 legged resilient channel is not specified by the Steel Stud Manufacturers Association (SSMA). So there are no standards for its construction or use.


So basically since theres no standards for its use, its never spec'd out on prints? Since hat channel is specified under the ssma and they do know how it will perform, it is used?

But dont you think resilient channel is still better over hat track even though its not specified under the ssma?


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## Sir Mixalot (Jan 6, 2008)

Rich D. said:


> So basically since theres no standards for its use, its never spec'd out on prints? Since hat channel is specified under the ssma and they do know how it will perform it is used?
> 
> But dont you think resilient channel is still better over hat track even though its not specified under the ssma?


The negative about it to me is if it will hold the load. Because every channel is different. 
Not a single tested standard.


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## Rich D. (Oct 14, 2011)

Sir Mixalot said:


> The negative about it to me is if it will hold the load. Because every channel is different.
> Not a single tested standard.


So your saying it may not be strong enough to hold up the wall assembly? Even rc-2?


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## Sir Mixalot (Jan 6, 2008)

Here's a link to the SSMA's--> Product Technical Guide 2012


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## Sir Mixalot (Jan 6, 2008)

Rich D. said:


> So your saying it may not be strong enough to hold up the wall assembly?


No. It probably is strong enough. All I'm saying is, that it's unkown and a possible risk in certain situations.


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## Rich D. (Oct 14, 2011)

So basically since the ssma dosnt spec rc, its not used...


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## Rich D. (Oct 14, 2011)

Im not trying to argue btw. Im kind of confused about the whole thing. Trying to educate myself on these channels...

If you didnt have specs or prints on a job, would you use hat or rc-2? I would think rc-2 would provide a higher rated wall asembly...


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## Rich D. (Oct 14, 2011)

Heres an interesting article

http://soundproofing.org/infopages/channel.htm 

Heres a piece i cut out..

It is important to distinguish acoustically effective resilient channels (RC-1 RC-2) from hat channels, Z-channels and other lightweight metal furring systems that drywall contractors are used to installing. These other systems may resemble resilient channels, but they allow no movement and are simply too rigid to be effective. Only true resilient channels have any acoustical benefit.

Heres another clip..

For walls, the drywall edges should be resting on neoprene vibration pads and sealed with caulk before the wall is finish taped and painted. This provides a supporting base on which to mount the wall and Unload the channels from the weight of the drywall panels. Use 2 of the 2? pads per vertical sheet of drywall or, 1 every 2? or so.. The weight of the drywall will tend to crush the drywall edge down on the pad, narrowing the gap to the floor to be sealed. 

.....

That would help with taking weight off the wall...
....

But since theres no spec for it, you wont see it in commercial applications...


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## Sir Mixalot (Jan 6, 2008)

Rich D. said:


> Im not trying to argue btw. Im kind of confused about the whole thing. Trying to educate myself on these channels...
> 
> If you didnt have specs or prints on a job, would you use hat or rc-2? I would think rc-2 would provide a higher rated wall asembly...


Yes. I'm here to learn as well. :thumbsup:
I'd use hat. I worry most about ceilings with RC. But that's me.


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## Rich D. (Oct 14, 2011)

The reason im asking all these questions is because i have a 20x30 existing room i was asked to sound proof...

Im trying to improve my systems.

Sir, you made me want to look at other products and get away from rc channels...

Have you heard of sound isolation clips you mount to the studs, which accepts hat track onto and then use that to screw the boards on in between joists..

http://www.greengluecompany.com/products/noiseproofing-clips

That combined with a layer 5/8 rock, green glue, then another layer of 5/8 with roxul is the stud voids should make a nice quiet wall.


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## builder49 (Feb 24, 2010)

Sir, Rich & others. Thanks for the interesting and informative replies. Will look into the hat channel etc. Due to space limitations, I was hoping to avoid building out the existing walls too much. I was hoping to just add a couple of layers of 5/8" with "green glue" sandwiched in between. I would like to reduce the sound transmission but achieving a 2 hr fire rated assembly is my goal. Thanks and Merry Christmas to all. builder49


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