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acyate 02-21-2009 11:08 AM

Creating a soundproof wall question
I share a common wall with another tenant in an apartment and the sound transmission is very poor. I've talked to my landlord and he is ok with me putting a temporary soundproof wall as long I take it down when I vacate.

I've come up with creating a separate wall ( 2 X 4 studs @ 24" oc with 5/8" sheetrock on the sides, no insulation). I'm trying to keep cost at a bare minimum and estimate that the project can be done for under $100.

The wall assembly will weigh about 350 lbs. It will not be attached to the existing wall but will be a few inches away from it to allow for dead air space to increase sound dampening. It will be in the dining room area.

My question is - will a 350 lb load be significant load to the existing structure?? I'm not on the ground floor and the building was probably built in the 70's (lead paint era). I could probably bring the weight to under 300 lbs be switching to 1/2" sheetrock but this would effect the sound absorption of course. As far as other loads in the dining, nothing really other than small dining table and a couple of chair.


Bob Mariani 02-21-2009 11:32 AM

You will have no problems with this additional weight. You still have sound transmission from the ceiling and floor. use a foundation sill insulation under the bottom and top plates and side wall studs. Also keep the drywall away from the floor, walls and ceiling leaving a small 1/4" gap. Then caulk this gap.

acyate 02-21-2009 11:59 AM

Thanks Bob,

The sound transmission through the floor is a concern for me. The floor is hardwood and I can even hear the creaking noise on the floor when the neighbor walks. I read somewhere that as much as 30% of sound can be transmitted through the ceilings and floors. Too bad I won't find out how effective the wall would be until after the fact.

Just a few more questions if you have the time -

- is the weight really not a factor? I'm not sure what loads the building was built to, the only thing I'm worried about is that all the weight of the wall assembly will be concentrated uniformly in one area rather than spread out.

- can I get by with using normal silicon caulking rather than sound absorbing caulking such as the green glue type?


Termite 02-21-2009 12:30 PM

You can only expect a sound decrease of maybe 10 decibles with the addition of this wall. That is rather insignificant. Bob's idea of using foam sillsealer to set the wall on is a good idea....I'd use at least a couple layers. What kind of caulk you use shouldn't make much difference.

Bob Mariani 02-21-2009 03:48 PM

weight is not an issue. You are not adding much and you are spreading it out over the whole floor. Did you loose any fat friends in this area? As posted any caulking is fine. Latex may be easier to use. Tool with a plastic spoon to get a nice smooth joint. Prime with PVA primer for the new drywall. You could use soundproofing drywall as an extra buffer. Also padding and carpet in your apartment will help. Add a white noise generator to the area?

Willie T 02-21-2009 04:42 PM

I'm laughing, Bob. As I read down - before I go to your post - I was thinking about asking if a 350 man standing in one spot would stress his floors. :thumbup:

Termite 02-21-2009 06:12 PM

I agree, weight will absolutely not be an issue.

acyate 02-21-2009 06:20 PM

Well, maybe I was being a bit overly cautious about the weight.

I'll look into the PVA primer. Soundproofing drywall will probably blow my budget. If I need to beef it up, I might have to go with sandwiching another layer of drywall with some greenglue.


Based on what I've read, a 10dB reduction might not be that bad. Right now, the sounds I'm hearing are like I have a roommate living in my bedroom.

Bob Mariani 02-22-2009 07:05 AM

Two layers of drywall will not nearly match the sound proofing drywall. Let alone doubling your work which needs to include loading and unloading and carrying into the apartment.

Termite 02-22-2009 09:52 AM

For every additional layer of 5/8" drywall, plan on about 4-6dba reduction.

Bob Mariani 02-22-2009 10:33 AM

Soundproofing drywall like QuietRock is offers 10 times more STC than the same size drywall. Also good idea to use 24" OC joists with unfaced batt insulation between the studs. Soundproofing drywall offers an STD rating of 51, doubling your drywall offers a rating of 36. listen to the exact same noise level with these files. cost of two sheets of drywall are about $25, soundproofing is about $39 Labor savings more than makes up the difference in cost of a much less solution.

Hmmm. files did not load... try this link to hear samples.

Brandon_NC 02-22-2009 11:00 AM

Would a "blow in" insulation be easier? You would just need to fix the drywall after the installation. Is the wall already insulated?

Sound Proofing

acyate 02-22-2009 12:28 PM

The wall is already insulated and I don't want to touch the existing wall.

As for the quietrock, thanks for link. It was nice to know what to expect from the sound reduction. Do you recommend one layer of quietrock on one side only as opposed to a layer of drywall on each side of the wall?

One other thing I came across is to stagger studs -

Instead of using 2 X 6 plates, I'm going to try to keep the 2 X 4 plates and rotate the 2 X 4 vertical members 90 degrees.

nap 02-22-2009 01:38 PM


Originally Posted by acyate (Post 234080)
I share a common wall with another tenant in an apartment and the sound transmission is very poor.

I realize what acytate meant but his wording implies he might want to listen to the neighbors;


the sound transmission is very poor
I think he meant the sound isolation or sound insulation is very poor. Having poor sound transmission is what he is seeking, I think.:whistling2:

as to the sound transmitted via the floor; not much you can with that. The floor joists are common members so you have a direct mechanical link with the neighbor you cannot sever. Same with ceiling.

Rugs and carpet are about the only thing available to help with the floor. If the ceiling is a drop ceiling, that can be insulated to reduce sound transmission but if a hard ceiling, not much you can do there.

the staggering studs are for a common wall so you do not have the rock on each side connected to the same stud, which provides a direct solid connection between the two sides. Since you are building a separated wall, the gain would be minimal if you are using rock on each side but worthless if using only one sided wall.

one additional method you can employ not yet mentioned is the use of "hat channel" It is a material installed on the studs and the rock attached to it. It reduces the contact of the rock to the wall and as such, aids in sound isolation.

Bob Mariani 02-22-2009 03:08 PM

again look at the link and what I have mentioned. As posted above by Nap, you are not dealing with staggered studs. Placing on both sides does add to sound reduction, but not physically possible without loosing a lot of space in your room. Hat channel (resilient channel) is a cheap way to add sound transmission by adding to the existing wall but will still not nearly be effective as what I explained. and would do nothing to the new wall. One of the sound tracks even covers this. You are to add batt R13 to the new 2X4 wall that you wanted to build. Leave it loose. Use unfaced not krafted.

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