# Soundproofing



## holmesismyhero (Jun 6, 2011)

I'm starting a new job in an older stripmall, and it includes building a demising wall between my clients unit and what will be a neighboring tenant. Her usage is dog grooming / doggie daycare, so the landlord wants the wall to be soundproof.

I'm going to do a 2x6 top and bottom plate with staggered 2x4 construction, and sound insulation between. My question is, would it make sensee to also use the sound proof drywall as well? At $50 extra per sheet, on a wall that will use 20 sheets, that's a grand we can save if its not going to make that much of a difference. 

I've seen reports that show the sound deadening drywall is as effective using conventional construction as regular drywall in a staggered stud construction. Would using both be even better?

Suspenders and a belt, I guess. I might compromise, and do the bottom 4 feet with the soundproof drywall, as thats where all the noise will be coming from. 

Comments?


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## overanalyze (Dec 28, 2010)

Soundproofing a wall or floor takes a good plan from framing all the way through drywall. Most sound is not the sound itself coming through the wall rather vibrations from the sound. If the wall you are building is the only common wall between the units, having a common top and bottom plate will still allow vibrations to transfer from one side to the other. You may have better luck building two complete separate walls...if space isn't an issue. Just he sure to check if the building dept wants a layer of fire code drywall in between the assemblies.


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## Ted White (Jun 23, 2009)

You would need to do the whole wall. Including any wall above the suspended ceiling, presuming there is such a ceiling.

Double stud is better than staggered stud, as mentioned. 

Standard fiberglass is all you should use. Nothing special. 

Same with the drywall. The specialty drywall you mention isn't heavy and that's what you want. Use a layer or two of standard 5/8" drywall


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## aptpupil (Jun 12, 2010)

any holes in the wall? you will want to seal them well, too.
holmes on homes did an episode on this, i would think you had seen it already. :laughing:


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## ohiohomedoctor (Dec 26, 2010)

That soundproof drywall is awesome. We use it on ceilings in basement media rooms. Its only around $30 here though. We tore one of those out a few years back. It was disgusting. Somehow dog hair filled some wall cavities and had made its way behind the frp board which veneered all the walls.


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## Ted White (Jun 23, 2009)

You might look at simply using double 5/8" drywall and a field application of damping compound. Much better results


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## Rusty Nails (Apr 3, 2005)

Here's a link to quite a few different sound assemblies. There's dozens of ways to get what you want with cost, room and level of sound protection being the criteria.

http://www.pac-intl.com/assy_dwgs_wl_wood.html 

I'm curious to how you were going to insert sound board between the 2x4 staggered studs with a 2x6 plate?


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## Fieldings (Sep 20, 2011)

Have you thought about the use of sound bar? That is what mostly goes on in my area. I think a staggered wall with Roxul Safe n' Sound and sound bar with 5/8 drywall would be best. I have done similiar applicatons with good results. The Roxul is fire and mold resistant as a bonus.


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## holmesismyhero (Jun 6, 2011)

The sound board is to be used instead of regular drywall on the bottom 4 feet of wall, where the dogs will be.

I think the staggered stud idea sounds like ti is optimal, it is only 2 inches wider than a standard wall (which affects rental area). While they do share top and bottom plates, it is the center of the wall that is the focus of the sound transmission. Top and bottom plate are secured to rafter and floor, which dampens the sound transmission. 

And yes, I saw the episode...


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## Inner10 (Mar 12, 2009)

> You might look at simply using double 5/8" drywall and a field application of damping compound. Much better results


And less money. Great solution. :thumbsup:


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## Big Shoe (Jun 16, 2008)

Ted White said:


> You would need to do the whole wall. Including any wall above the suspended ceiling, presuming there is such a ceiling.
> 
> Double stud is better than staggered stud, as mentioned.
> 
> ...


Ditto :thumbsup:


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## Ted White (Jun 23, 2009)

It's the whole wall, not the middle or the lower 4'.


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## RS Sam (Feb 9, 2009)

...and if the adjacent areas share a common floor it will help immensely to set the bottom plate cut in to interrupt that common floor.


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## Ted White (Jun 23, 2009)

If the floor is a slab, I wouldn't worry about it


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## TimNJ (Sep 7, 2005)

I agree with Fieldings. Roxsul SafenSound. Caulk the bottom plate to the floor.


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## Ted White (Jun 23, 2009)

You're not going to improve the performance by going beyong cheap fiberglass. That's a lab-documented fact. 

Perfectly fine to use whatever is cheap or available, but know that the performance will not improve. Use whatever is cheapest.


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## Fieldings (Sep 20, 2011)

Ted White said:


> You're not going to improve the performance by going beyong cheap fiberglass. That's a lab-documented fact.
> 
> Perfectly fine to use whatever is cheap or available, but know that the performance will not improve. Use whatever is cheapest.


Where is this lab-documented fact? Not that I don't believe you.... But I do find it extremely hard to believe that Roxul SafenSound doesn't have better soundproofing capabilities than traditional fiberglass insulation.


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## Ted White (Jun 23, 2009)

http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir766/ir766.pdf

Very reasonable question. The issue is that insulation ON a wall needs to have different properties than insulation IN a wall. So often we find that an insulation company will quote NC or NRC ratings, which are the surface absorption ratings (by frequency). In other words, how much echo the insulation will stop / reduce if mounted ON a wall. In this environment, the denser mineral wool wins every time.


When we're looking inside a wall, we're now considering low frequency (bass) isolation and we therefore look and see which insulation type performs best in the cavity in our wall or ceiling. When you plot out the various tests and look specifically at the low frequency response, the fiberglass shows a slight advantage. The NRC lab linked above did not collate the data this way, however you can pull the various lab reports yourself and see.

In reality, any insulation of similar density will perform similarly. The practical performance difference between lower density fiberglass and the slightly higher density mineral product is small. This is why I suggest buying whatever is cheaper.


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## Fieldings (Sep 20, 2011)

Ted White said:


> http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir766/ir766.pdf
> 
> Very reasonable question. The issue is that insulation ON a wall needs to have different properties than insulation IN a wall. So often we find that an insulation company will quote NC or NRC ratings, which are the surface absorption ratings (by frequency). In other words, how much echo the insulation will stop / reduce if mounted ON a wall. In this environment, the denser mineral wool wins every time.
> 
> ...


That is a lot of info to read, I'll get through in the next couple of days. Thanks for posting looks interesting. For the record I have never put insulation ON a wall, or even thought of it. Strange.


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## Ted White (Jun 23, 2009)

On a wall is mostly done in noise controlled environments like studios and theaters. Covered with acoustically transparent fabric.


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