Super Soundproofing Community Forum

Soundproofing Forum Topics => Soundproofing your Condo, Townhouse or Bed & Breakfast => Topic started by: zver1 on April 04, 2012, 11:44:28 PM

Title: making thin layered soundproofing drywall
Post by: zver1 on April 04, 2012, 11:44:28 PM
I have a 2x6 common wall which can not be made thicker but needs soundproofing.  Also has a return air duct running through it to make life more difficult.  Still trying to see if I can reroute the return air duct, but otherwise here is my plan:
1) putty pad all outlets/switches.
2) replace 2x6 16" apart with staggered 2x4s 8" apart(16" apart each side).  Weave 2 lbs mass loaded vinyl between studs and otherwise fill cavity with fiberglass.  Prior drywall was 1/2" which I can not exceed (wall continues as outside wall for a large stretch, has an outside door etc)
3)  Create a 1/2" sandwich of 1/4" concrete backer board+green glue+1/4 drywall.  This should be similar to quietrock or similar products which I can not find locally and do not want to pay for shipment.

Other people have put up 5/8" drywall, green glue and then another layer of 5/8"  While this is great, I do not have the depth available to do this.  My concern is whether the two 1/4" layers are stiff enough to squeeze the green glue when screwed together into 16" spaced studs or if there will be a problem of the 1/4" surface drywall becoming wavy as screws pull in at the studs and the center flexes outward.  Any experience with this?  Does the sandwich need to be assembled and compressed prior to install(much heavier to lift)?  If it is a problem, what is the minimum thickness of drywall that people have used successfully.
Title: Re: making thin layered soundproofing drywall
Post by: Randy S on April 05, 2012, 02:49:48 AM
This is actually not a bad approach based on your space restrictions. I actually think you could get a decent reduction out of this system, it will just require a bit more detail with the installation.

Just make sure you use a lot of caulking when sealing the barrier and I would shorten up the staple pattern to make up for the loss of mounting area for the MLV.

Install the hardie baker first and caulk ALL seams ( butter the edges as you install and wipe clean while wet) air tight, then apply green glue to back of sheet rock and install. Make sure you offset all seams from hardie backer to drywall the best you can.

Im not a drywall guy, But as the hardie backer is a very rigid product you shouldn't have too much trouble with the 1/4" drywall.

Just a side can always add 1/2" hardie backer or drywall with green glue inside the wall between the cavities against the existing wall to increase mass and use 1/2 drywall as the final.... depending on which direction is the source of the sound issue.
Title: Re: making thin layered soundproofing drywall
Post by: zver1 on April 05, 2012, 06:39:58 PM
In terms of making the soundproof drywall match up against adjacent wall areas, is there any way to estimate the thickness added to the wall by the green glue layer?  For it to be effective, I assume it must occupy space meaning there is a dept increase over the two layers of drywall/backer board.  A little difference can be made up in the tape and spackle phase, but would be nice to know in advance so can plan.
Title: Re: making thin layered soundproofing drywall
Post by: Randy S on April 05, 2012, 06:53:40 PM
1/16" to 1/8" max depending on a 2 or 3 tube per sheet formula.