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Soundproofing - adding drywall behind lathe for extra density

Hey GBA people,

I have a fun question regarding soundproofing.

The house is semi-detached and there is a 2x4 party wall. That needs some special attention for soundproofing. My plan is placing a 1 5/8 steel stud floating wall on my side of the party wall for decoupling and shafting. Filled with roxul safe n sound batting, MLV sheeting on the steel studs and 5/8 drywall.

Then I got sucked into an idea:

Could I place drywall caulked with acoustic sealant on the backside of the neighbours lathe to add density ? Kind of like having a double layer of drywall but one layer within the stud pays. Anybody see any problems with this?

Asked by Jamie B
Posted Sep 7, 2017 9:58 AM ET


3 Answers

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I could imagine your neighbor might not like you tampering with his/her wall. At a minimum, I would get a written release stating the neighbor agrees to this modification.

On your stackup, you might consider doubling the 5/8 drywall or attaching hat channel to the 1 5/8 studs for further decoupling. If there are any outlets in the wall, you would want to make them as airtight as possible.

Answered by Steve Knapp CZ 3A Georgia
Posted Sep 7, 2017 10:28 AM ET


Hey Steve,

Actually the neighbours are pretty supportive of soundproofing the party wall, since it benefits them as well.

But yes, I actually have an agreement with them already for other work.

I am considering/expecting to double layer the drywall on my side, it's something I can make a gametime decision on after the first layer is up and I do sound transmission testing.

Answered by Jamie B
Posted Sep 7, 2017 8:54 PM ET


If you decide to go with the drywall on the neighbour's lathe, you might want to set it in Green Glue.

Your plan sounds good. Unfortunately it's really hard to predict result on existing walls, but you sound like you have the bases covered.

Answered by Malcolm Taylor
Posted Sep 7, 2017 9:48 PM ET

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