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Discussion Starter #1
I am curious if this is a viable option... installing 1/2" plywood onto the walls with 5/8" sheetrock over the plywood.

Last dedicated room I hung two layers of 5/8" sheetrock, but it never failed when I was need something solid to screw to for whatever it might have been, where I needed to screw was outside of a stud. Anchor bolts are not too good on double 5/8" sheetrock.

My thinking is go ahead and hang the plywood, then the sheetrock, which gives me solid anchoring no matter where I need to hang something, including acoustic panels, screen frame, pictures, speakers, or whatever.

It seems like this would give the room a little more solidity as well.

Are there any drawbacks, other than it will cost a little more?

Thanks!
 

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Hey Sonnie

I've had people do that before. Just understand that while it's more massive than single drywall, it's not as massive as 2 layers of drywall from an isolation standpoint. You can still use Green Glue between the layers to good effect though.

Bryan
 

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WOW, talk about weird, I came to the same conclusion about using the plywood for the very same reason! As a matter of fact I was just going to start my HT build thread and was just looking around before ( I get easily distracted ) I post. I just finished hanging 30 sheets of 1/2 plywood today! What A job, and man do I feel it! I will explain in more detail in my thread but I screwed the plywood to the metal studs along with liqued nails and then using silicone to seal all seams and recepticals. the next layer will be 60 mil Bituthane from Grace and then the 5/8 drywall.

Rick
 

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OSB would be my preference over plywood. By design it is more dense and has a better ability to shed moisture.

As to adding a vapor barrier [Bituthane ] between layers, this is never a good idea. Your structure[current residential building]should have a proper vapor barrier system according to the wall assembly of said building.

In interior barrier does not allow the interior wall to work with the current assembly. Remember, vapor moves from the warm side to the cold side, so anywhere you stop it, be prepared to have a way for it to be extracted from the assembly.

Living in Montgomery, AL, depending on if you have a brick or siding exterior, you already have one of two types of vapor retarder systems in place. Brick having a back venting and siding having some type of drainage plane house wrap.

Either of these two allow the assembly to dry towards the outside of the structure.
 

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Discussion Starter #5
Bryan... I had never heard of Green Glue, but it sure sounds interesting.

It is my understanding the plywood and drywall have approximately the same STC rating. I think I may go with 5/8" plywood, then 5/8" sheetrock. Then on the house side, where you see the hallway below, I will go with two layers of 5/8" sheetrock, then put two layers of R-13 (R-26 total) in the staggered stud wall. That should pretty much silence the HT room from the house.



I could go with 11/16" OSB instead of plywood, it would be heavier.

There is material called SheetBlok that is a specific type of sound isolation barrier that is only 1/8" thick (STC-27), which is equivalent to 1/2" sheetrock. However, after reading up on Green Glue, it sounds like it will work better.


Rick... that is strangely coincidental, is it not? Great minds think alike. :whistling:

Brien... you can take turns helping Rick and I both with our construction. :bigsmile:
 

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Green Glue will absolutely work better than Sheetblock - and is cheaper per square foot to boot.

Just remember that STC completely ignores below about 200Hz - all the places where it's hardest to stop. STC is great for classrooms, etc. where you're primarily stopping utilities, speaking, etc. Completely different than stopping [email protected] from a subwoofer.

Bryan
 

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Discussion Starter #7
Whoa... that Green Glue ain't cheap. Just to do the one wall is 2 cases at $320... to do the hallway wall and the ceiling is 5 cases at $800. :yikes:

Any idea where I might get it for less than $160 per case of 12 tubes?
 

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I have it a little cheaper but not much. It's just expensive. Look at 1lb Mass Loaded Vinyl though (sheetblock) - it's a LOT more per square foot and shipping is silly expensive. Green Glue usually ends up being about 1/2 of what MLV is and it performs a lot better.

Green Glue standard coverage is 192 sq ft per case (2 tubes per 4'x8' sheet). You can use 1 tube per, cut your cost in half, and get about 2/3 of the performance.

Bryan
 

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Discussion Starter #9
I thought it was 3 tubes per sheet.

So... you guys sell it... cool. I did not see it on your site.

I will buy it from you though. :T
 

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3 tubes per sheet gives you maybe 10% more performance for 50% more money. 2 tubes is what I recommend. PM me when you're ready.

Bryan
 

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A lot of prefab housing (timber frame, modular, kit homes, SIPS, etc) pre-make wall units that are 2x4 or 2x6 with insulation and OSB on both sides. The outer wall can have siding, stone, brick etc, and the inside can have wainscoting, drywall, etc with little fuss. There's always something to nail to.

OSB is cheaper and better suited to wall applications than plywood. It's not as heavy, but it will work. One drawback is that you'll need special outlets or outlet extenders for all the boxes, but people deal with multi-layers of drywall, so those products are out there.

I've used Green Glue with mixed results. In one application where the room was very well isolated, it worked great. In my bedroom common wall, not so great. The sound was still able to "short" through other means and we can still hear our noisy neighbor. I blame our house's construction more than the Green Glue, though.

Good luck.
 
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