# Sound Proof Common Wall



## bbbuilders (Mar 28, 2006)

I am remodeling a townhome where each unit shares a common wall. The wall is wood frame 2x4s. Nothing fancy. Now that I have demo'd the unit down to the studs, what is the best way to rebuild the common walls to reduce sound transmitting from one unit to the next?


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## Bob Kovacs (May 4, 2005)

Depends on how much space you want to lose, but you also have to make sure you maintain the fire-rating of the wall assembly with whatever you do. You'll need at least one layer of 5/8 Type X drywall for one-hour fire resistance, you may need two by code. Obviously, more drywall will create more mass, and more sound dampening. 

You can also hang the rock on resilient channel (RC-1 channel), which will help further- but you have to make sure the assembly is fire-rated. You'll also lose around 1/2" with the channels.

Or, you can create a staggered stud wall and weave sound batts thru that, followed by the channels and drywall- you'll lose a few inches doing that though.

Bob


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## K2 (Jul 8, 2005)

20 years ago I did 4 townhouse style apartments and still own them. I did 2 full walls between units fully insulated and the walls don't touch each other. I saw cut the plywood between the units so the plywood could not transmit sound etc. I consider this one of the smart things I did 20 years ago. You don't hear anything between units.


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## RobertCDF (Aug 18, 2005)

All the walls I have seen in these types of situations are double walls. 5/8" drywall on the inside with a small space in between then finish as normal. Insulation, drywall, blah blah. More or less just repeating what has already been said by others. (maybe I should just shut up)


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## Spectatorz (Jun 11, 2004)

*SoundProof Walls*

I would hang a layer of 3/8" dry wall on the studs and then a layer of 3/8" sound board (available at big orange) then finish the wall with 1/2"drywall.
If you want more quiet, go with 1/2" sound board instead.
Works Great, I have used this method myself.

Just my opinion.


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## RowdyRed94 (Jan 23, 2006)

I just did a bunch of research into this to decide how much to put into our model home. The advice above is spot on with what I learned. I'd add that it's futile to attempt to isolate low-frequency sound. Thuds and thumps will always get through to some extent. 

This forum thread spells it out quite well. Read Brian's posts.

http://www.avsforum.com/avs-vb/archive/index.php/t-452667.html

My problem was that everyone says "this works great" and "that worked for me", but how often do they really know? Only the person who lives in the home really knows. We've put money into sound channel, soundboard, fiberglass, and whatever else, but we never really get to experience the results.


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## K2 (Jul 8, 2005)

I lived in one of my townhouse units for 2 years. dbl wall works great. I think cutting the plywood floor between the walls is important.


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## alvector (Oct 24, 2007)

*quietrock and mlv*

I just got done installing Quietrock and mass loaded vinyl in a new 8500 sqft home. We put the quietrock on the ceilings of the first floor, and walls in the master suite. In the tile areas we used the mass loaded vinyl. Both perform very well. You can tell the difference when the guy in the other room is using a saw, or someone is upstairs. Note, we also had cotton insulation installed in all ceilings with a floor above. I'm not on the billing end of it, but I know that the quiet rock is quite expensive. Did research on it myself, and the only thing better (according to research) is a double wall with mlv woven and cotton batts. I can see cutting the plywood flooring (sub) would help, but only if the joists ran with the cut,, but then i would worry about the strength of the sub to carry the weight of the wall.


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## MonsterToys (Oct 25, 2007)

*sound proof room steps*

Ive done something similar to this guys' steps in sound proofing a room (before or after putting up the walls:

ehow.com/how_15992_soundproof-room.html

However, in my experiences, it is very difficult to make it 100% sound proof. The key is to choose a material that will absorb sound well. Hopefully this helps in your research.


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