Building from scratch - 25 x 25 ft - need advice

Hello, I am building a new rehearsal studio, 25x25x9 from scratch and it needs to be 90-something percent soundproof for loud rock music. There is a dizzying array of options on the internet. So far it looks like Green Glue or equivalent and 5/8 drywall is the way to go for cost effectiveness vs. damped sheetrock. A few questions: 1. Is a double wall necessary to make a room "soundproof" (where neighbors can sleep through the noise, they are between 100-200 feet from where the room will be; we are separated by retainer walls, in some cases two)? 2. Or, can I simply use two 5/8" type x drywall + Green Glue + "resilient channel"? Three/four drywall sheets? I forgot to mention, I'm getting the drywall for free. (I'm trying to avoid building a double-wall) 3. The outside of the building will be stucco, should I design the outer walls in a particular way? Keep in mind, nothing has been built, there's not even a foundation. The plans have been approved and I could still modify them.

Hi "Gstring". Welcome!

1. Is a double wall necessary to make a room "soundproof" (where neighbors can sleep through the noise, they are between 100-200 feet from where the room will be; we are separated by retainer walls, in some cases two)?

For isolating drums? Yes, you will need a proper two-leaf "room-in-a-room" approach. Drums and bass are the most difficult instruments to isolate, due to the very high levels and very low frequencies involved. 100+ feet of space between you and the neighbors is good, but low frequencies carry far, especially at night when thing are quite in the neighborhood.

There is a dizzying array of options on the internet.

Yup! But not too many of them are based on real science! Way too many are based on myths, guesses, and plain old ignorance. You wont find those here on this forum. Just the real stuff that actually works, and has been tried and tested in laboratories and the real world.

2. Or, can I simply use two 5/8" type x drywall + Green Glue + "resilient channel"? Three/four drywall sheets?

That us still a 2-leaf "room-in-a-room" approach, just not quite as effective. In order to decide which specific technique and materials to use, you first need to set a goal for your isolation, in real numbers. You need to define how many decibels of transmission loss you need. That will lead you directly to the type of building technique and the exact materials, thicknesses and dimensions that are necessary for attaining that level of isolation.

(I'm trying to avoid building a double-wall)

But you just described two cases of double wall! :)

3. The outside of the building will be stucco, should I design the outer walls in a particular way?

Yes: with plenty of mass, and sealed air-tight.

Keep in mind, nothing has been built, there's not even a foundation. The plans have been approved and I could still modify them.

Excellent! Then you are in the best and most enviable position of all: you can do it right, from the beginning! :)

it needs to be 90-something percent soundproof for loud rock music.

90% isn't much. 90% soundproof implies a transmission loss of less than 20 dB. A couple of sheets of cardboard will do that! :) Most people don't realize that sound and our ears work on a logarithmic scale, not a linear one. You are going to need something like 60 dB of isolation (plus or minus a few), which implies a reduction by a factor 1,000,000. Yup, you need to get it about a million times quieter than it is, in order to achieve what you want.

So far it looks like Green Glue or equivalent and 5/8 drywall is the way to go for cost effectiveness vs. damped sheetrock.

Sheetrock and drywall are the same thing, just by different names. And what Green Glue does is actually a form of damping: constrained layer damping (CLD) to be more precise. You always need to damp the resonance in an MSM wall, and Green Glue accomplishes that in a certain specific part of the spectrum, for a specific mode of resonance, but you still need insulation (fiberglass, mineral wool, etc.) to damp the resonance of the cavity itself. You can't do without damping on an acoustic isolation wall: it will cost you as much as 16 dB of isolation, or even more if you also don't use Green Glue. - Stuart -

Stuart, Yes, there will be drums and bass. Aren't drums and bass in the 110-120 dB category? Maybe this is a silly question to ask, but why not just stack a bazillion panels of drywall together? Okay, up to five? ...six?!? Would that be as effective as a double leaf setup? Also, regarding the double leaf system, STC 69: http://www.bobgolds.com/WallCharts/Quad ... eafSTC.htm My concern is, how will this affect the perimeter wall that will have stucco? Will I still need two sheets of 5/8 drywall on the first, outer-stucco wall (as shown in the link)? And if so, won't I have to modify the plans? Or should I just walk up to the sub contractors, offer them some coffee and donuts and say, "hey, you don't mind hanging up two sheets of drywall to the whole building before you start there...do you?" :mrgreen:

Yes, there will be drums and bass. Aren't drums and bass in the 110-120 dB category?

Yup! And most likely your local municipal noise regulations will say that the maximum legal limit at night is around 40 dB, maybe even 30. 120-40=80. So you need 80 dB of isolation. ( Maybe 90! :shock: ) That's pretty extreme. An average house wall (sx4 studs with drywall on each side) gives you 30-something. Call it 40, to be nice. Isolating 80 dB is 10,000 times harder. You need to absorb ten thousand times more energy to stop 80 dB as you do for 40 dB. The math is simple, but the numbers are shocking!

Maybe this is a silly question to ask, but why not just stack a bazillion panels of drywall together? Okay, up to five? ...six?!? Would that be as effective as a double leaf setup?

A bazillion would work! But five or six? Not. If you don't use MSM isolation, then you are stuck with the principle of physics called "mass law". Mass law says that each time you double the mass of a wall, you get an increase of 6 dB in isolation. So start with your standard 2x4 wall with a single layer of drywall on each side, at 40 dB isolation. Add an extra layer to each side, you get 46 dB. So now you have two layers per side. Double that again to get 4 layers per side, and you hit 52 dB. Double again (8 layers per side) and you are at 58. Double again (16 layers per side) and you hit 64.... I think you get the picture! :) Most people do not realize just how hard it is to stop very loud sound, especially if it has a lot of low frequency content!

Also, regarding the double leaf system, STC 69:

What you see there is a comparison, not numbers written in stone. To get the truth about how to get STC-69, refer to IR-761. And STC is a lousy way of measuring isolation anyway, as it does NOT take into account low frequencies. It cuts off at 120 Hz, so it doesn't even consider things like kick drums, bass guitars, the lower few octaves of keyboards, etc...

My concern is, how will this affect the perimeter wall that will have stucco? Will I still need two sheets of 5/8 drywall on the first, outer-stucco wall (as shown in the link)?

I wouldn't put drywall on the outside leaf of a house. I'd replace that with something like OSB. But you can use whatever material you need to get the same surface density.

And if so, won't I have to modify the plans?

Probably, but that shouldn't be a big deal. You are not changing the dimensions, shape, style or other major aspects of the house: just changing materials. Shouldn't be an issue. Call your municipality to find out: you might not even need to change the plans. - Stuart -