John Sayers' Recording Studio Design Forum Archive

Hello friends,

I am a Columbia College Audio and Acoustics graduate (concentration in production, not acoustics), and I've been studying studio builds for sometime now, with the ultimate goal of creating my own, professional, home studio eventually. This forum has provided me with so much information, it'd be wrong for me to continue without at least offering my sincere thanks, so on that note, thank you all, for your time and wisdom are greatly appreciated!

Moving on, I've been at war with myself for a couple years here, trying to compile a thread worthy of this forum, but I've changed plans so often, it's probably better that I didn't waste anybody's time in the duration.

My build is taking place in my detached garage (approximately 40'x25'), where I raised the attic height to 10', instead of 6', where it used to be, to offer more height in what has evolved to be the location for my control room. I also replaced the old attic ladder with a nice new staircase, to my satisfaction. Acoustically speaking, I've done little to win the isolation war up there, but it's been ok so far, regarding neighborly complaints and impeding sound sources, such as planes and Harley Davidson's being captured on tape, for example (though mic pre gain is quite low when I'm tracking heavy metal guitars, haha, so bleed doesn't exist much in that regard); voice narration on the other hand, not so happy about the ambient noise levels up there.

Some details about my attic space- I have a gable type roof, with 2x12" rafters, one layer of 3/4" plywood, and architectural asphalt shingles. I used rafter vents to send ambient air from the soffits to the ridge. On the interior, I left the rafter collar ties (2x8"s) exposed, thinking aesthetics, and diffusion (maybe useful). I used 1 1/2" resilient channel to secure each section of drywall upstairs, and only applied one layer of 5/8" gypsum to the channels, where I should've done two with green glue, but it just didn't happen, as I was overly stressing it's completion, unfortunately.

Unfortunately, again, I find myself in a hurry to construct a small tracking room on the ground floor, and again, I have a relatively tight budget to get it operational, though I am qualified to build it myself, and I am willing to take out a small loan (couple thousand), to get it done as good as possible, on my budget.

HVAC should've been my step one, but has yet to be designed, and is not yet in my budget. Luckily for me, the building is very well insulated, and maintains it's temperature very well, even with my gear on...it could be better though, surely. Pushing the HVAC back was definitely a mistake on my behalf, but I have some plans to get around it, without having to destroy much of the finish work I've done. In time...

So, with that all said, and a vast amount left unsaid, you may understand how I'm feeling about getting this done. Ultimately, I wouldn't be surprised if this thread spirals out of control, but hopefully not, as my frustration has me in a corner where I'm just about to build some walls and hope for the best.

At this moment, I'm curious about one specific item, which pertains to the tracking room I am going to build under my control room.

This room (about 14'x12'x8') will be constructed in a corner on the ground floor of my garage, and will be divided from my workshop/car area. Currently, two of the (eventual) four surrounding walls are exterior walls (2"x6" wood studs that are fiberglass insulated, with 1/2" OSB and vinyl siding on the exterior). There is currently 5/8" drywall on those two interior walls, and one of those walls also has a soffit on the exterior that I am concerned about.

Armed with both solid information and disinformation, I find myself fighting logical explanations.

In terms of simplicity, I'd like to leave up the existing drywall (because why not?), drill a bunch of holes in it (thinking Helmholtz and anti-resonance), maybe install hat channel/clips over it (to slightly decouple the interior and exterior walls), then triple layer 5/8" gypsum/green glue as my final application. I am partially aware of the leaf effect here, but again, I understand the theory more than the application...and yes, I recognize it would not be the ideal two leaf as would be preferable, thus the extra gypsum.

Would it be better to rip down the drywall, then do resilient channel/clips straight to the 2"x6" framing, to increase STC/isolation, and decrease resonance?

This is essentially the first question I'm looking to understand more thoroughly. Please let me know what you think, and if you have any other words of wisdom, advice, criticisms, etc., please let me know, I'd really appreciate it.

Thanks in advance, and sorry for the book length introduction.

CHEERS!

The garage door faces East. The console faces North. The stairs are on the Southwest end of the building.

I plan to partition off the garage door/shop area from the tracking room area with a long wall.
There will also be a hallway/entraceway from the exterior door, with two doors inside, one for studio access, the other for shop access.

Inside of the wood 2x4" studs on the ground will be my main tracking area. The blue tape represents future walls as well.

Sorry, the no cad..

Welcome!

As you can read in almost every other single thread on the forum, the first question is, how many dB of transmission loss are you needing for you studio space? You mentioned recording metal guitar and voice over. Both of those don't have super low frequency information like a bass amp or drum set.

So you have (or want) a live room on ground floor and a control room above it?

You also mentioned that you want a professional grade home studio. That will probably mean you need great isolation from room to room and the outside world. That means building rooms in rooms. Your current construction sounds like a standard garage and acoustically speaking, that won't be sufficient. You'll need to rip off the drywall, re-use what you can to beef up your exterior sheathing with green glue and cleats. From there, build you inner leaf.

Until we see SketchUp drawings and real life pictures, I have no idea what your room upstairs looks like so I cannot comment on it. This will also help us grasp where your staircase and things are.

Greg

Hey Greg,

Thanks for the quick reply!..I'm currently trying to squash pics to upload, but apparently the website is very picky about photo file size. Secondly, my cad skills are lacking, but I should have some pics that illustrate some of what I have, and some of what I'm going for.

Regarding your questions about information I haven't provided (sorry about that), I'll do my best to give you what I can, though I'm no acoustician, more like an overzealous student.

Your very first question about transmission loss is an objective question where unfortunately, I only have a subjective answer, and by that, I only mean that I am unsure of the ratings I truly need.
I've read many posts here, and abroad, which already have me second guessing how I could've approached this thread differently, just by that simple question which I should have had a simple answer for. Damn.

Anyhow, yes, I will be tracking instruments with full frequency information/dynamic range, such as drums, bass, and piano, for example.

...when I said professional, I should've chosen a better word, such as, ''high quality,'' as I don't have the means to build what I consider to be a professional studio inside of my detached garage, at this point in time. I am willing to accept that I am going to have some isolation problems here, I'm just hoping to do the best that I can with what I have. That word was misused.

...and yes, I'm looking to build a live room at ground level, beneath my control room.

Your statement about beefing up the exterior walls flipped a switch in my head, that may be easier than I have envisioned.

I'm between a rock and hard place regarding my live room layout, as I'm hoping to build with acoustic proportions in mind, think C.P. Boner for example. My room, off memory is about 14x12x8, which follows one of C.P.' s proportions accurately...if I start doing room in room designs (the most obvious and beneficial for isolation, I know), my proportions go down the drain, then tuning, etc, becomes much less fun.

Already, you have glitched my brain, for the better, why thank you, I'll do my best to get some pics up asap.

Thanks!

Thanks for posting pictures. It all makes sense now!

Are you okay with having poor isolation from the outside world into and out of your control room?

If only super loud sources like drums will be tracked on the main floor room, you could save money by just building that room as a room in a room.

Greg

Absolutely Greg, I was rushing to get pics up before anyone replied, haha, definitely makes more sense with a visual.

...and yes, you are spot on with that question/assessment, as I am not entirely discouraged by the poor control room isolation, like I am with the live room downstairs, which I'd definitely be looking to seal as best as possible...without a full blown remodel anyhow, haha..

I figured the mass spring mass, leaf conversation would come sooner than later.

The way I visualize it, the two exterior walls are my biggest problem, regarding my strict limits for proportionally planning a small room, finances of course, and time constraints...the other walls that I plan to put up will hopefully contain pressure more effectively than if they weren't there, but I understand resonance, and therefore understand the battle ahead of me.

Thanks for spitballing with me, you've already helped me gather some productive thoughts.

Cheers!

-Chris

Hi, Chris, and Welcome to the forum!

HVAC should've been my step one, but has yet to be designed, and is not yet in my budget. Luckily for me, the building is very well insulated, and maintains it's temperature very well,

It seems you want good isolation? If so, the temperature issue is not the number one issue with HVAC: staying alive inside your studio is! In order to get good isolation, you need to seal your room totally, hermetic, twice over. Completely air-tight. Putting people inside there to perform means that there's no fresh air going in, no stale air going out, and no humidity control. People exhale moisture in large quantities, and CO2 in even larger quantities. You have to get rid of that. CO2 level will kill you long before the oxygen runs out.... HVAC in studio is mostly about getting stale air out, fresh air in, and humidity control Temperature control is secondary (but still important).

In other words, it's your VENTILATION system that needs your attention.

In terms of simplicity, I'd like to leave up the existing drywall (because why not?),

Because isolation! If you proceed as planned, you'll have the sum total of practically no isolation: 1/2" OSB plus vinyl siding is pretty much useless for studio isolation. Not even as an outer leaf. You'll need more mass on that.

drill a bunch of holes in it (thinking Helmholtz and anti-resonance),

Unless it is designed and built specifically to be a Helmholtz resonator, it won't be. And even if you did design it that way, what frequency would you tune it to? And why?

maybe install hat channel/clips over it (to slightly decouple the interior and exterior walls), then triple layer 5/8" gypsum/green glue as my final application.

So your wall would be: 1/2" OSB, 5 1/2" air gap, Helmholtz resonator INSIDE the wall ( ) 3/4" air gap, 3x 5/8" drywall. Is that it?

I don't even know how to calculate the isolation from that. The Helmholtz resonator in the cavity is a HUGE unknown. I've never even heard of anyone doing that, nor can I even think of a reason why you would want to. And of course, at the resonant frequency, the wall would not isolate at all.

I am partially aware of the leaf effect here,

There isn't any in this case, since your "middle leaf" is a Helmholtz resonator that has a very deep cavity on one side and a very thin cavity on the other side. No idea how to model that. One side si tuned deep low down, the other is tuned high. Plus the overall MSM resonance. It's not 3-leaf, but it sure as hell ain't gonna isolate so well!

and yes, I recognize it would not be the ideal two leaf as would be preferable, thus the extra gypsum

If you did do a 3-leaf, then the extra mass needs to go on the MIDDLE leaf, and the other two leaves need to have roughly equal mass. That's the optimum layout, and the one that the simple equations work for. Having more mass on one of the outer leaves and practically none on the outer is not going to work too well.

Would it be better to rip down the drywall,

Yes, absolutely.

then do resilient channel/clips straight to the 2"x6" framing,

No. Not if you want high isolation. You'd need a second independent frame for that.

to increase STC/isolation,

Increase isolation: Yes. Increase STC: irrelevant. STC is not a useful measure for determining studio isolation. In fact, its a rather useless measure! It only considers HALF of the musical spectrum, to start with.

and decrease resonance?

What resonance are you wanting to decrease, and why are you wanting to decrease it? In what way do you want to "decrease" it? Frequency? Amplitude? Something else?

This is essentially the first question I'm looking to understand more thoroughly. Please let me know what you think, and if you have any other words of wisdom, advice, criticisms, etc., please let me know, I'd really appreciate it.

First things first: As Greg said: define your isolation needs, in decibels. Without knowing that, it's all just guess work, which has a 99.9999% chance of being wrong.

The garage door faces East. The console faces North. The stairs are on the Southwest end of the building.

Without having an accurate, dimensioned diagram of what you are talking about, there's not much I can say!

but apparently the website is very picky about photo file size

Keep it under 700 pixels wide, and you should have no problems.

my cad skills are lacking, but I should have some pics that illustrate some of what I have, and some of what I'm going for.

Forget CAD. Just do a simple model in SketchUp.

Your very first question about transmission loss is an objective question where unfortunately, I only have a subjective answer,

Then you need to get an objective answer! It's dead easy to do. All you need is a half-decent hand-held sound-level meter (but NOT an app on your iPhone: a REAL meter).

I only mean that I am unsure of the ratings I truly need.

Then MEASURE them! A sound level meter and a few hours work are all you need.

Anyhow, yes, I will be tracking instruments with full frequency information/dynamic range, such as drums, bass, and piano, for example.

Drums is a different ball game. That's major sound energy at low frequency. Hard to deal with. So you REALLY need to get the sound level meter out, and start testing!

I'm just hoping to do the best that I can with what I have.

Then your single most important aspect is design! It's that simple. If you don not spend the time to design it right, then it won't be much good. If you just sort of try to throw a few bits of construction material together, in haphazard ways, without doing the math, then I can guarantee you that the outcome will be disappointing at best, and unusable at worst.

You have a good sized space, with good potential. If you spend the time to DESIGN it right, it can be better than you are hoping for. But if you don't, it won't even rise to that level.

I'm between a rock and hard place regarding my live room layout, as I'm hoping to build with acoustic proportions in mind, think C.P. Boner for example.

It's a LIVE room: Why do you want to use a ratio for it? And why that particular one? Ratios make little sens for live rooms....

is about 14x12x8, which follows one of C.P.' s proportions accurately

No it does not. Not even close. That's 1 : 1.5 : 1.75. Not very close at all to Boner's ratio, which is 1 : 1.26 : 1.59 Waaaaay off.

if I start doing room in room designs (the most obvious and beneficial for isolation, I know), my proportions go down the drain, then tuning, etc, becomes much less fun.

Once again, this is a LIVE room, so why do you think it needs to follow a ratio? It's NOT a control room, so why bother? Why worry about ratios when isolation is a much, much bigger issue?

I figured the mass spring mass, leaf conversation would come sooner than later.

You are not making much sense with that comment! You already discarded the concept of building a room-in-a-room, since you say it would trash your room ratio, so where would you get any MSM if you don't have two leaves?

The way I visualize it, the two exterior walls are my biggest problem, regarding my strict limits for proportionally planning a small room,

Once again, I don't understand your fixation on wanting good proportions for a LIVE room.... Why? For what purpose? I'm not following the plan at all. Why do you need your live room to have a good ratio? Please explain.

the other walls that I plan to put up will hopefully contain pressure more effectively than if they weren't there,

Pressure? Are you building a water tank? Why do you want to contain pressure? What type of pressure? Air pressure? Water pressure?

but I understand resonance,

With all due respect, I don't think you do. Where would you have any MSM resonance if you only have a single leaf wall around your studio? There's nothing to resonate... There would only be MSM resonance if you build a room-in-a-room system. If you only have a single leaf wall, then you are doomed to lousy isolation, no matter how good that wall is. If you want good isolation, the only logical choice is room-in-a-room, but you don't want that because you are chasing a ratio, even though it's just a live room.

This isn't making a whole lot of sense to me right now! I think it would be better if you take the time to draw up an accurate diagram of what you have in mind, labeling each part clearly, with dimensions. With that, we can figure out what you are actually trying to do, and help you come up with a plan.


- Stuart -

Hello, Stuart, thanks for taking the time to respond so thoroughly, your expertise and guidance are greatly appreciated; I've read hundreds of your posts on this forum, and I couldn't be more enthused to finally chat with you about my build!

I will do my best to illustrate how and why I am thinking about things the way that I am, and I really look forward to identifying any falsehoods that I've been led to believe, because I am certainly aware that my acoustical knowledge is diluted with misinformation, thus why I am finally posting here, after many years of study from the sidelines.

Let's begin a little out of order here, so we can simplify our conversation a bit.

Quote:
I'm between a rock and hard place regarding my live room layout, as I'm hoping to build with acoustic proportions in mind, think C.P. Boner for example.
It's a LIVE room: Why do you want to use a ratio for it? And why that particular one? Ratios make little sens for live rooms....

Quote:
is about 14x12x8, which follows one of C.P.' s proportions accurately
No it does not. Not even close. That's 1 : 1.5 : 1.75. Not very close at all to Boner's ratio, which is 1 : 1.26 : 1.59 Waaaaay off.

Quote:
if I start doing room in room designs (the most obvious and beneficial for isolation, I know), my proportions go down the drain, then tuning, etc, becomes much less fun.
Once again, this is a LIVE room, so why do you think it needs to follow a ratio? It's NOT a control room, so why bother? Why worry about ratios when isolation is a much, much bigger issue?

Quote:
I figured the mass spring mass, leaf conversation would come sooner than later.
You are not making much sense with that comment! You already discarded the concept of building a room-in-a-room, since you say it would trash your room ratio, so where would you get any MSM if you don't have two leaves?

Quote:
The way I visualize it, the two exterior walls are my biggest problem, regarding my strict limits for proportionally planning a small room,
Once again, I don't understand your fixation on wanting good proportions for a LIVE room.... Why? For what purpose? I'm not following the plan at all. Why do you need your live room to have a good ratio? Please explain.

Firstly, the above posts allude to an idea that I am fixated on my decision to utilize room proportions for the construction/design of my live room, and in hindsight, I obviously make it seem that way, but I didn't hope to imply that to be the case, as it was meant to be more of an idea seeking approval, which it was not, thankfully; with your simply stated question, "it's a live room, why use a ratio," I have gathered that proportional planning is a waste of my time/resource, and would actually be a major hindrance for my build, as it now appears quite obvious.

I was under the impression that ratios were valuable for both live rooms and control rooms, especially smaller ones, but it seems clear that I am wrong in that assumption. Moving on.

It seems you want good isolation?

Yes, I absolutely want good isolation.

HVAC in studio is mostly about getting stale air out, fresh air in, and humidity control Temperature control is secondary (but still important).

In other words, it's your VENTILATION system that needs your attention.

I understand that ventilation is a critical piece of the equation, but I wasn't thinking of it as simply as you put it, which will definitely change my approach.
Already, there has been a paradigm shift in my thinking.

Quote:
Would it be better to rip down the drywall,
Yes, absolutely.

Again, we can shorten this discussion significantly with my acceptance of the fact that I will need to increase the exterior wall mass, though now, I have some new questions...

Quote:
In terms of simplicity, I'd like to leave up the existing drywall (because why not?),
Because isolation! If you proceed as planned, you'll have the sum total of practically no isolation: 1/2" OSB plus vinyl siding is pretty much useless for studio isolation. Not even as an outer leaf. You'll need more mass on that.

So far, I've never established a plan that I was dead set on, which I'm sure is apparent, and my questions are evolving as I begin to recognize the fundamentals that have eluded my approach.
At this point in conversation, with some newfound wisdom, am I wrong in thinking that my outer leaf (those two exterior walls), at this moment, consists of vinyl siding - 1/2"osb - 5 1/2"insulation - 5/8" gypsum? If I were to glue two more sheets of 5/8" gypsum on the interior of those two exterior walls, would that still be a poor outer leaf? I understand the vinyl and 1/2" osb aren't great, but wouldn't any application of mass on the interior become beneficial to that leaf as a whole, in this example? I am a little confused about that. Aside from ripping down the vinyl/osb and replacing it, is there an approach I can take, to make it more acceptable from the interior side of things?

First things first: As Greg said: define your isolation needs, in decibels. Without knowing that, it's all just guess work, which has a 99.9999% chance of being wrong.

Forget CAD. Just do a simple model in SketchUp.

Then MEASURE them! A sound level meter and a few hours work are all you need.

Sometime soon, I will get an SPL meter to establish my isolation needs, and will do my best to create a model of my building in Sketchup.

Thanks again, I'm already seeing things more clearly. Cheers!

I was under the impression that ratios were valuable for both live rooms and control rooms, especially smaller ones, but it seems clear that I am wrong in that assumption. Moving on.

For a control room, yes, ratios are important: but not nearly as important as some people think: It's just one of many aspects that need to be taken into account when designing a room. For a live room, they are only useful in the sense of avoiding the really terrible ones, such as where two dimensions are identical or directly related (eg, 16 feet long, 8 feet wide and 8 feet high). As long as you don't have any direct mathematical relationship, there's no need to go crazy trying to find a "perfect" ratio for a live room. Instead, live rooms are SUPPOSED to have "character" and "warmth" and "vibe", and all those other things that make them attractive to musicians. So if you are stuck with a ratio that happens to favor a certain set of frequencies, use that to your advantage: just keep it under control, and don't let it "run away with the show", by taming it with treatment.

Yes, I absolutely want good isolation.

Good! Then you should start your design process by defining that: How many decibels of isolation do you need? That's a very important number, since it sets the stage for the entire build. So get a decent sound level meter (part of this thread tells you what to look for: http://www.johnlsayers.com/phpBB2/viewt ... =3&t=21122 ), and measure how loud you are in your current setup, for a typical session. Then measure how quiet you need to be, both from a legal point of view (local noise regulations) and also from a practical point of view (what level does your family consider "acceptable"? And your neighbors?). The difference between those two is how much isolation you need. From there, it's simply a matter of looking at the various types of construction that will provide that level of isolation, and choosing the one you like most.

If you live in a noisy area (close to a major road, railway, airport, noisy neighbors, industrial area, sirens, helicopters, etc.) or if you have noisy weather issues (thunder, heavy rain, wind, hail), you might also need to consider isolation in the other direction, to stop those external sounds getting in.

I understand that ventilation is a critical piece of the equation, but I wasn't thinking of it as simply as you put it, which will definitely change my approach.

In simple terms: Your ventilation system needs to move at least 6 times the total air volume of your room, every hour, and better is 8 times the volume. That should be recirculated through the room, but then you need to bleed off a certain percentage of that and throw it away, to the outside world, while replacing it with the same percentage of fresh air. That percentage depends on occupancy: how many people are in the room? They all consume oxygen from the air, and dump CO2 into the air, with every breath. The harder they are working (playing music), the more O2 they need and the more CO2 they expel. So you need to do the math to figure out what the highest and lowest numbers will be for that "percentage" of the total air flow, that needs to be dumped and replaced with fresh air, to keep things pleasant inside... and indeed, to keep you alive! You will die from CO2 poisoning long before you die from lack of oxygen....

However: consider that installing the ducts to move that air in and out implies chopping huge holes in your isolation walls! Thus, you need to build "silencer boxes" to deal with that problem. A silencer box allows the air to get through, but stops the sound from getting through. You need at least one and probably two of those on EACH duct.

am I wrong in thinking that my outer leaf (those two exterior walls), at this moment, consists of vinyl siding - 1/2"osb - 5 1/2"insulation - 5/8" gypsum?

That's your outer TWO leaves! Technically, a "leaf" is any "sandwich" of heavy, solid, thick building materials that are all together, with no air between them: so your "vinyl siding plus 1/2" OSB" is one leaf, but the insulation doesn't count as part of a leaf since it is mostly air, then comes the other leaf, which is the single layer of drywall. So that's 2 leaves, not one. Yes, they are coupled together by the studs, so that's NOT a good isolation wall, even though it is two leaves. That's why you need to pull of the drywall from inside, and then use that (the drywall you pulled off) to "beef up" the outer leaf, by placing strips of that in between the studs, up tightly against the OSB that is currently your outer leaf. That adds an extra layer to the "sandwich", so that it now consists of "vinyl siding plus 1/2" OSB plus 5/8" drywall", which means that you have a LOT more mass on your outer leaf, which is good. There's a special technique for attaching that drywall: you CANNOT simply nail through it into the OSB! And you cannot glue it, either... When you are ready to do that, ask, and we'll explain.

If I were to glue two more sheets of 5/8" gypsum on the interior of those two exterior walls

Gluing layers of drywall to each other is a bad idea, for many reasons. First, acoustically: it is far better to just have the layers next to each other, WITHOUT gluing, as that allow them to act independently as well as together. Secondly, glued drywall can "de-laminate", and come apart over time, with the paper covering separating from the gypsum core, then falling apart... not a happy thing! So do not ever glue drywall layers together.

Also, just adding more layers of drywall to a COUPLED 2-leaf system is not going to be very effective, precisely because the two sides are coupled! You need to add mass to the outer leaf, and get rid of that coupled inner leaf, then build a new inner-leaf that is NOT coupled.

I understand the vinyl and 1/2" osb aren't great, but wouldn't any application of mass on the interior become beneficial to that leaf as a whole, in this example?

ONLY if it is added to the leaf itself: in other words, in direct contact with the existing layers, so they are all right next to each other, with no air (or insulation) in between. You can have as many layers of mass in your leaf as you want, but they must be built up like a sandwich: layer on layer on layer, in direct contact.

Aside from ripping down the vinyl/osb and replacing it, is there an approach I can take, to make it more acceptable from the interior side of things?

There's no need to rip down the OUTSIDE. You need to rip down the INSIDE anyway, and you can use that to add mass to the outside, from within the wall, between the studs. This is often referred to as "beefing up" the outer leaf, and it does not require that you remove the exiting outer leaf: you just add more mass to it.

So, once you have your outer-leaf complete, as just one single "bunch" of mass around you, on ALL sides of the room (all four walls, and the ceiling) then you can build your inner-leaf within that shell, and you do that by putting up new framing, that does NOT touch the existing framing at any point: not even a single nail. So your new wals framing stands on the floor, without touching the existing walls OR the existing ceiling, then you frame up a new ceiling on top of those new walls, and that new ceiling ALSO does not touch the existing walls OR the existing ceiling. And you put drywall on only ONE side of that new framing. You might need more than one LAYER of drywall, but they all go together on just one side of the studs, as a sandwich, just like the outer leaf.

Thus, the inner-room is completely independent from the outer room. No mechanical connections at all.

That's the basic concept.

If your inner-room is not going to fill the entire area enclosed by your outer-leaf, then you'll need to build an extension of the outer-leaf across that space, to enclose the part that you do plan to use.

For example, let's say you have a basement, and you want to leave part of it for just a basement, but use the other half to have three rooms for your studio. You would do it like this:
The left part is the basement section, and the right part is the studio section, enclosed by the isolation wall that divides the two areas. The the three rooms are built inside, each as a single leaf.

On the other hand, if you only wanted one smaller room for your studio while leaving most of the basement open, then you would do it like this:
In both cases, you can see how the extra wall was built to define the studio area, then the inner leaf room(s) was/were added as single-leaf construction.


- Stuart -

I can't thank you enough, Stuart, already, you have helped me tremendously!

Happy Monday!..., so I have a couple quick questions, and one clarification..

Quote:
If I were to glue two more sheets of 5/8" gypsum on the interior of those two exterior walls
Gluing layers of drywall to each other is a bad idea, for many reasons. First, acoustically: it is far better to just have the layers next to each other, WITHOUT gluing, as that allow them to act independently as well as together. Secondly, glued drywall can "de-laminate", and come apart over time, with the paper covering separating from the gypsum core, then falling apart... not a happy thing! So do not ever glue drywall layers together.

Initially, when I said, "glue," I really meant to say green glue, which I have realized is quite different from one another. With that in mind, when beefing up my outer leaf for mass, would it be ideal to green glue each layer of drywall (if that's the material I choose to use), or does it make little difference?...expanding on that question, I have access to a bunch of free ply/osb sheets, and was curious if wood offers the same quality of "beef" that drywall does, in this application, between studs on the interior of the building? That would be nice if it did.

Also, I am unclear about the preferred method of installation of any extra interior leaf materials, which you mention at the bottom of the post below...

Quote:
am I wrong in thinking that my outer leaf (those two exterior walls), at this moment, consists of vinyl siding - 1/2"osb - 5 1/2"insulation - 5/8" gypsum?
That's your outer TWO leaves! Technically, a "leaf" is any "sandwich" of heavy, solid, thick building materials that are all together, with no air between them: so your "vinyl siding plus 1/2" OSB" is one leaf, but the insulation doesn't count as part of a leaf since it is mostly air, then comes the other leaf, which is the single layer of drywall. So that's 2 leaves, not one. Yes, they are coupled together by the studs, so that's NOT a good isolation wall, even though it is two leaves. That's why you need to pull of the drywall from inside, and then use that (the drywall you pulled off) to "beef up" the outer leaf, by placing strips of that in between the studs, up tightly against the OSB that is currently your outer leaf. That adds an extra layer to the "sandwich", so that it now consists of "vinyl siding plus 1/2" OSB plus 5/8" drywall", which means that you have a LOT more mass on your outer leaf, which is good. There's a special technique for attaching that drywall: you CANNOT simply nail through it into the OSB! And you cannot glue it, either... When you are ready to do that, ask, and we'll explain.

I have gathered that cleats and side nailing are the idea here?...I'd love to understand that method clearly, if you wouldn't mind elaborating a bit.

Thanks.

when beefing up my outer leaf for mass, would it be ideal to green glue each layer of drywall (if that's the material I choose to use), or does it make little difference?

You can look up the technical documents on Green Glue's website. You'll learn that the stuff is pretty magical. It offers great results without eating up space. It's really easy to install, much easier than adding more layers of heavy material. Basically, it's highly recommended.

I have access to a bunch of free ply/osb sheets, and was curious if wood offers the same quality of "beef" that drywall does, in this application, between studs on the interior of the building? That would be nice if it did.

Awesome. Use them. Wood does offer the same "beef" that drywall does, just differently. By differently, I mean that different materials have different surface densities. The reason drywall is often used is because it has the best cost to mass ratio. The only downside to you using something like plywood over drywall is that in order to obtain the same mass, you will have to use thicker/more layers of plywood. Thicker beef up material = smaller gap between your masses of your MSM system (unless you move your inner leaf further from your outer leaf which would also result in a smaller room). Heck, if we all could afford it, I'm sure we'd use materials like lead for our walls.

I have gathered that cleats and side nailing are the idea here?...I'd love to understand that method clearly, if you wouldn't mind elaborating a bit.

I think you're completely understanding the procedure. Put up your beef up material (with GG between if you choose to do so) and press it up as tightly as you can. Install the cleats to hold the material in place. Obviously, seal around each layer with GG Sealant. That's it. It's a pain in the ass job, but obviously worth it.

Greg

The reason drywall is often used is because it has the best cost to mass ratio. The only downside to you using something like plywood over drywall is that in order to obtain the same mass, you will have to use thicker/more layers of plywood.

Right! The density of drywall is around 680 kg/m3, while the density of plywood is only around 560 kg/m3. So you would need plywood that is 22% thicker to get the same mass. MDF is actually better than drywall: around 750 kg/m3. But it's also quite a bit more expensive. OSB is similar to plywood but a bit better: around 600 kg/m3. So you need OSB that is around 15% thicker to get the same mass as drywall.

Heck, if we all could afford it, I'm sure we'd use materials like lead for our walls.

For sure! Lead sheeting is around 12,500 kg/m3! Yep, you read that right: About EIGHTEEN TIMES the density of drywall. So instead of two layers of 5/8" drywall, you could have a sheet of lead foil just 1/16" thick, and still have the same total mass. Lead is also "limp mass", which makes it even better for isolation.... on the other hand, it ain0t cheap, and is difficult to work with. However, there are some rather specialized products out there, that consist of thin lead sheeting embedded in drywall. Used for shielding places where radiation is a problem, such as hospital X-ray rooms, MRI and NRM rooms, science labs where radiation is an issue, etc. You can buy that stuff for your studio if you want: Huge amount of mass in a thin panel. But huge price tags, too!

The normal recommendation is plain old 5/8" (16mm) fire-rated drywall, because as Greg mentioned, its the best compromise on price: reasonably high mass, lowest price per kg (or pound) of mass. It's also easy to work with. But there are alternatives, if you have lots of money and a need to save space. Even steel plate is good, at around 7,800 kg/m2 (11 times density of drywall. So is aluminium plate: 2,800 kg/m3 (4 times density of drywall). It's all about cost/benefit.

Obviously, seal around each layer with GG Sealant.

Sealing is critically important, yes, but I'm not to keen on GG sealant. The actual GG compound is the best stuff out there, bar none, but their sealant isn't so good: it tends to shrink a bit as it dries, so it can crack if you apply it thick. And if you apply if thin, you need two or more layers... There are better sealants out there. So, to be clear: Green Glue compound between layers of sheeting: YES! Absolutely. Green Glue sealant: Not so much. Use alternatives.


- Stuart -

Stuart, this is an alternative here in my area. It's wicked messy though. It's roughly the same price as GG Sealant. Would you recommend I switch to it for future sealing?

PL Acousti Seal

I have already had some of my GG Sealant crack on me and it wasn't very thick

Greg

I have already had some of my GG Sealant crack on me and it wasn't very thick

Yup. Their flagship product is amazing. Not so much their sealant.

Not sure if you can get it in your area, but I've had pretty good results with Sikaflex f11C. It's a multi-purpose sealant and adhesive, basically meant as bathroom/kitchen caulk, but it sticks like crazy to most surfaces, and is very flexible when cured (Shore A 45). Easy to work with (Ok, it's messy like all caulks) and doesn't shrink much or crack as it dries. Dries to the touch in a couple of hours, and fully cured in a couple of days. It has worked fine for me on many projects. If you can find it, buy a tube and do some tests, to see if it will work for you.

https://usa.sika.com/dms/getdocument.ge ... 1FC-us.pdf

- Stuart -