Impossible to Soundproof Bedroom Wall From Neighbours Decked Area?


Postby SomeGuy99 » Tue May 29, 2018 1:54 pm

Hello,

I'm trying to understand why all my efforts to soundproof a wall in our bedroom keep failing.

Here's the situation; Our north wall is 46ft long, 1 and half stories high (half the lower level is in the ground), no windows or doors. All our bedrooms and bathrooms run along the wall. Directly on the other side of this wall is our neighbors deck (about 5-6 feet away). When they're on the deck talking and yelling, we can hear them... all night

Originally, this wall had 5/8 drywall, 2x6 framing, fiberglass insulation, 1/2 osb, 1.5in Styrofoam, vinyl siding.

To start fixing this, I simply added a layer of 5/8 CertainTeed SilentFX drywall in our bedroom. The claim from them is that it "features a viscoelastic polymer between two specially formulated dense gypsum cores significantly improves sound attenuation and is ideal for systems requiring high STC performance." It was super heavy stuff. I installed it over the existing drywall with a gap all around the edges which I filled with acoustic sealant. This helped a little but we can still hear the neighbors talking and yelling.

I found out that the OSB on this wall had a lot of rot due to the Styrofoam not being sealed. My thought was that the rotten OSB (lack of mass), was letting a lot of noise through, like an open door. Also, it seemed to me that Styrofoam can amplify sound (I can share some youtube video's to show what I mean). I tore down the outside of this wall, replaced all the OSB, sealed all cracks and gaps, then replaced the Styrofoam with Rockwool Comfortboard 80 (suppose to absorb sound). After doing all this... there was NO change in the amount of noise coming in. I was totally shocked.

Am I cursed? Or is there something else I've missed? Based on the STC rating of the drywall alone, I shouldn't be able to hear anyone talking normally. Yelling should be murmurs.
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Postby fenny666 » Mon Jul 09, 2018 7:19 pm

Hi, I know it's an old post but It's one I may be able to assist with and might still be relevant.

I'm not a sound proofing specialist and without looking at the problem i'm working on the assumption that the wall is the only culprit that needs to be addressed in order to resolve the issue.

I'm not familiar with the specialist board you have used but the thing that stood out to me was that it was fixed directly to the existing partition. The key for better acoustic performance is to reduce the amount of vibration allowed to travel through the partition.

There's a few approaches I would try -

I suspect the specialist board was expensive. Are you able to remove it? If so, fixing it differently should almost certainly improve its performance. One approach would be to use res bar fixed to the exsisting wall and the boards are fixed to this. Res bar is designed specifically to improve acoustic performance. Go to BG website and look in the 'white book' for res bar which will better explain what this is. But don't be put off, it's dead easy.

A bullet proof approach (again assuming the wall is the only culprit) but more expensive and if you can afford to lose the space would be an independent wall lining.
I would build a 50mm stud partition in front of the wall ensuring a 10mm gap between the exsisting wall and the back of the wall lining.
Ideally you should use 'I' studs because as you are only boarding one side they are far more rigid. You could use 'C' studs which are cheaper but will likely need bracing to the exsisting wall to stop it flexing.
When fixing the floor and head track you should fix 2 50mm strips of soundblock to each and then fix them. To better explain this imagine it would look like ceiling, then 2 layers of board then the track. Acoustic sealant should be used between each layer. Its not normally required do this on the floor track but it wouldn't hurt.
Fix the studs at 600mm centres and fill between the studs with 50mm Knuaf acoustic insulation. Then fix res bar horizontally at 600mm centres. Then board. If you can reuse your specialist board then try a layer of this. To improve further add an additional skin of 15mm soundblock and even a second skin.
Be sure to stagger board joints horizontally and vertically and acoustic sealant should be used round the perimeter.

Long winded I know.

Hope this is helpful.

Cheers
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