Bulking up exterior walls

[cprescott1972]

Greeting! I'm wondering if adding mass to the exterior walls of a pre-existing garage would be a good idea or not. I'm planning on pulling the drywall off anyway before I build the new interior studio room. Thinking that maybe installing some 5/8" drywall to the interior wall cavities might help stop some of the low freq transmission.
The big IF here is whether that will cause a mold/moisture problem. I'm pretty sure it would help sound wise. I just don't want to have to tear things down 5 years down the road if there's a mold problem from bad planning.

Right now I believe it's exterior stucco >> wood paneling >> 2x4 framing with pink r-13. So, I'd plan on adding a layer of drywall to the interior framing between the insulation and the wood paneling.

Any thoughts?

[Soundman2020]

Most definitely! That is often known as "beefing up" the outer leaf, and is VERY worthwhile. Basically, you take out the insulation that is currently in the stud bays, then cut strips of 5/8" drywall to fit between the studs, up tight against the wood sheathing (probably OSB?), then you carefully caulk it in place all around the edges of each piece of "beef", and use cleats to hold the drywall in place (nail the cleats sideways into the studs). Depending on how much isolation you need (in decibels) and what the tuned frequency of your MSM system will be, you might even need two layers of "beef". If you search the forum for things like "beefing up", then you'll likely find numerous examples of how people have done this in their studios.

There should not be any mold or moisture issues from doing this, provided that you do it correctly and most important of all, that you place your vapor barrier in the correct position within the wall.

installing some 5/8" drywall to the interior wall cavities might help stop some of the low freq transmission.

It's not just about stopping low frequencies: rather, it is about tuning the MSM resonance of the wall correctly, and having enough mass and air gap, such that the wall attenuates all frequencies to the correct amount for your needs. Adding mass to a leaf re-tunes the MSM resonance, and that's the key to the whole isolation issue. Beefing up the outer leaf won't do much at all unless the inner-leaf is also properly designed such that both leaves work together correctly, as a tuned system.

- Stuart -