Metal Building - Inner Room Construction

I'm about to add a mix room and a performance room to my existing garage (see attached photos). The new addition will have 26 gauge metal siding, like the existing garage. As the photos show, the inner construction will be a "room within a room." The inner walls/ceiling will be lined with double 5/8" gypsum with Green Glue in between. * Will standard R13 insulation work for my interior walls or do I need Roxul Safe & Sound insulation? * Do I need a single layer of gypsum on the "interior side" of the "exterior" wall or will the 2" air gap be sufficient? I apologize if these questions appear dumb. I've spent countless hours of research and haven't found anything definitive. Thanks a million for any help!

"The inner walls/ceiling will be lined with double 5/8" gypsum with Green Glue in between. * Will standard R13 insulation work for my interior walls or do I need Roxul Safe & Sound insulation? * Do I need a single layer of gypsum on the "interior side" of the "exterior" wall or will the 2" air gap be sufficient?" Well...you need to explain your isolation needs first. As you may or may not be aware mass is the critical element in developing a well isolated environment. So 26 gauge metal is neither here nor there. As a system, a mass/air/mass or room in a room needs to be developed with all things being equal. So if you have decided that you will install two layers of 5/8 inch fire rated sheet rock on the interior then you should expect that you will do the same on the exterior. In respect to R13 or Roxul safe and sound...kinda calling apples apples at this point. Either one will do the job since all you are trying to do is damp the sheetrock panels and mitigate the air space resonance. But I must add, the single layer of gypsum on the "interior side" of the "exterior" wall is an inaccurate placement. What you are in effect doing here is massing up the exterior. So you do not place the layer(s) on the interior side of the exterior wall assembly but add them, in cut up pieces, directly to the farthest most point of the exterior wall assembly. Pretty standard.

Thank Brien for your response. I appreciate the detail in which you responded. I should have been more clear on my question of insulation. The question was in regards to cost. Standard R13 is much cheaper than Roxul Safe & Sound. Roxul sells itself as being more sound absorbing but I've read that some of it is just hype. Thank you for your detailed drawing of the exterior wall. However I'm confused on why the drywall is installed in pieces like that. I've read where insulation should never be compressed. Placing drywall panels in this fashion would compress my exterior R13 insulation. Thanks for your help so far!

The acoustic characteristics of insulation do not depend on marketing hype. They depend almost completely on a technical characteristic of the insulation known as "gas flow resistivity" (GSR). That refers to how well the fibers that make up the insulation resist the flow of gas (ie. air) moving through them. GSR is measured in units called Rayls, and if you know what those units are for the type of insulation you will be using and its thickness, then you can calculate the coefficients of absorption for any frequency, using the equations of physics. Yes, different manufacturers can do different things to their insulation to make it behave in different ways acoustically, but all that they really accomplish is to change the GSR of the product in one way or another (as well as changing a couple of other minor things). Unfortunately, not all manufacturers of insulation test or publish the GSR numbers for their products. The reason is simple: it's a measure that is mostly useful in acoustics, not much use in thermal issues, so if a manufacturer makes products for the thermal insulation market, it's understandable that he wouldn't bother testing or publishing figures that have no meaning for that market, any more than he'd test it for electrical resistance, or its ability to swat flies. Fortunately, there is an approximate relationship between the destiny of each type of insulation, and it's gas flow resistivity. If you know the density of the product, and what it is made of, then you can pretty much guesstimate what the GSR number would be. It won't be accurate, and the relationship is not linear, but it's clos enough to be useful. It turns out that for products made from fiberglass, the optimum density for use as a damper in MSM walls is about 30 kg/m3, and for products made from mineral wool, the optimum density is about 50 kg/m3.

However I'm confused on why the drywall is installed in pieces like that. I've read where insulation should never be compressed. Placing drywall panels in this fashion would compress my exterior R13 insulation.

Take a closer look at the diagram Brien made for you: it does not show any insulation at all yet, neither compressed nor uncompressed! I'm not sure why you thought there would be insulation in there, between the drywall and the metal. If there was any insulation in there, then that would create a multi-leaf wall (3-leaf in this case), which would REDUCE the isolation in the low frequencies, as Brien already pointed out. In other words, a wall with more than two leaves in it will have WORSE isolation than a wall with only two leaves in it, all other factors being equal. The very reason you cut the drywall into strips that fit in between studs is to ensure that you do NOT create any extra leaves. The drywall strips go up tight against the strips of foam sheathing, which are cut in the same way, for the same reason. That foam is closed-cell, not open-cell, so it does not create an air gap, which insulation would do. Your insulation comes AFTER you have beefed up the outer-leaf in this manner. You press it into place in the gap between the studs AFTER you put up the strips of drywall, so that it effectively fills the air gap between this leaf (your outer leaf) and the new leaf that you will build next to it (your inner leaf). Brien did not show the insulation for clarity, so you can see the correct way to add mass to the outer leaf. The other thing he didn't show, is the caulk. All the joints around the edges of the drywall must be caulked air-tight, before you put the battens (a.k.a. "cleats") in place. One other point: depending on your target for isolation (ie, how many decibels do you need to stop), you might need more than one layer of drywall in there. You didn't say what your goal is for isolation, but you will need to know that so that you can calculate the total amount of mass that you'll need on each of your leaves, and also the size of the air gap that you'll need to have between the leaves. - Stuart -

Hello Stuart. Thanks for your response.

I'm not sure why you thought there would be insulation in there, between the drywall and the metal.

I wasn't referring to Brien's drawing. I was referring to my drawing which shows insulation and metal on the outside of the stud wall. Most all Pole Buildings of this type use this method of insulating the structure. I now understand the negative impact of this three leaf issue. But now I'm clueless on how to proceed. Brien's drawing does not depict the 2x4 side girt that the metal siding is fastened to. (as does mine, see photo). If I were to install the drywall between each stud, I would still have the 1.5" thickness of the side girt between the drywall and the metal/insulation. Should I replace the 2x4 side girt with two layers of 3/4" OSB or Plywood? I've read that using wood for my mass can cause resonance in the mid range.

One other point: depending on your target for isolation (ie, how many decibels do you need to stop), you might need more than one layer of drywall in there

My house is about 150 feet away from the upcoming studio, which will be used primarily for mixing. With the cramped space requirements, I planned on putting 2 layers of drywall on the interior wall and 1 layer of drywall on the exterior wall. I'm anxious to get your opinion on the double layer of OSB or Plywood on the exterior wall.

" I'm anxious to get your opinion on the double layer of OSB or Plywood on the exterior wall." In an effort to have the interior wall assembly remain vertical, OSB is recommended, one layer, on the interior of the inside wall assembly.

Brien, pardon my ignorance but I'm totally confused on your response. My question about OSB was in regards to the "exterior" wall. Also, what are you meaning with the phrase:  "the interior wall assembly remain vertical" ?

One other thing. I've been looking at pictures we've all seen regarding wall leafs and STC. The image below is from Bob Gold's website: http://www.bobgolds.com/WallCharts/Quad ... eafSTC.htm There is the double leaf wall with an STC 57 rating. The triple leaf to it's left shows a STC rating of 50. Maybe I'm reading this wrong but it appears that the triple leaf assembly is not BAD but simply less isolation than the double leaf assembly. With the corrugated metal siding attached to the 2x4 side girt shown in one of my previous images I don't think I can avoid a triple leaf assembly. Any thoughts?

Maybe I'm reading this wrong but it appears that the triple leaf assembly is not BAD but simply less isolation than the double leaf assembly.

Right: You ARE reading it wrong! :) That diagram shows STC- ratings, which do not take into account the bottom two and a half octaves of the musical spectrum, nor the top two and a half octaves of the musical spectrum. STC only considers a narrow range in the middle, which roughly corresponds to human speech and typical house, office, school and shop sounds. That drop from STC-57 to STC-50 does NOT mean that you get 7 dB less isolation: It's far worse than that. (And even if it did mean that the reduction is 7 dB, that's still a huge amount.) Did you also notice that the 3-leaf wall in your diagram is not only 7 points worse but that it also has 50% more mass than the 2-leaf? There are three panels of drywall on the lousy 3-leaf STC-50 wall, but only two panels on the much better 2-leaf STC-57 wall... That should tell you something about how bad 3-leaf walls are, since even though they have much more mass, they still isolate worse. It works like this: walls are tuned systems. They resonate at certain frequencies, and do not isolate at all at and around those frequencies. They only isolate for frequencies above 1.414 times the resonant frequency. With a 3-leaf wall, the resonant frequency is much higher than for the same 2-leaf wall, and in fact for 3-leaf walls there are TWO resonant frequencies, not just one, where BOTH of them are higher than for a 2-leaf wall. So a 3-leaf wall will ALWAYS isolate worse than a 2-leaf, all other factors being equal. And the part of the spectrum where it will isolate worst of all, is in the low frequencies. Frequencies such as kick drums, toms, snares, bass guitars, the low end of keyboards and electric guitars, some types of percussion, etc. In other words, you get the greatest losses exactly in the area where you need the most isolation for a studio. The reason why you see "only" a 7 point drop in the STC rating, is because STC does not take any of those frequencies into account! The very bottom end of the STC scale is slightly affected, yes, but the STC scale ends roughly where the most important frequencies start. But the basic point here is that you are guessing, and seem to be trying to find reasons to justify not doing what we are suggesting you should do if you want good isolation. And that's fine! If you really don't want to do what needs to be done for maximum isolation, then nobody is going to force you to do that. You can build it any way you want, as long as you are prepared to live with the consequences. The reason I say you are guessing at how your walls should be built is because you still haven't defined how much isolation you even need, in terms of decibels. Until you do that, there's no way of knowing if your plan will provide insufficient isolation (most likely), too much isolation (highly unlikely), or just right. The correct way to design your isolation plan is to start with the number of decibels of isolation that you need, as tested with a sound level meter, then to either calculate (using equations) or look up in the literature, the types of wall, ceiling, floor, door, window and HVAC construction that will get you the number you are looking for. So your first order of business should be to figure out what that number is in your case. And it isn't an STC- rating number that you need, but rather a total transmission loss number (or better still, a full-spectrum TL graph) that shows exactly how much your "loud" needs to come down to be acceptable "soft".

With the corrugated metal siding attached to the 2x4 side girt shown in one of my previous images I don't think I can avoid a triple leaf assembly.

What type of "insulation" is that, shown in yellow? If you do end up with a 3-leaf wall, then it isn't the end of the world: it is possible to compensate for the lost isolation by re-tuning the wall back to the same frequency it would have had if it were just a 2-leaf wall. You accomplish that tuning by increasing the mass on each of the leaves, and/or by increasing the depth of the two air cavities, such that the 3-leaf f+ frequency is the same as or lower than the 2-leaf f0 frequency. The equations for figuring that out are not too hard to work through, if you like math. Or if you don't like math, then here too you can look up 3-leaf walls in the literature to find one that gets you the level of isolation you need at the frequencies where you need it. But do be aware that in order to adjust the 3-leaf wall to get the same isolation as the 2-leaf wall, you will need to spend a lot more on materials, and you will also lose a lot of extra floor space (since your walls will be thicker over all) and lose a lot of extra ceiling height (since your ceiling will also be thicker). The optimum arrangement for a 3-leaf wall is where most of the mass is on the middle leaf (the middle leaf must have the same mass as the other two leaves combined), and the two air cavities are the same size as each other. - Stuart -

rblythe wrote:

Brien, pardon my ignorance but I'm totally confused on your response. My question about OSB was in regards to the "exterior" wall. Also, what are you meaning with the phrase:  "the interior wall assembly remain vertical" ?

My first reaction would be that where I am, 5/8" fire rated sheetrock is less expensive than a 5/8" OSB per square foot. With the more uniform density of fire rated sheetrock and the ease of cutting and installation this is what I would use. To construct an interior framed assembly that is not attached to the exterior in any fashion you have to develop a method to make the interior wall assembly remain vertical...upright...standing up and not falling over. For years people have used decoupling mechanisms that attache to the exterior and to the interior wall assembly in the attempt to support the interior wall assembly, not connected to anything of the exterior wall assembly. Mostly a generic, one-size-fits- all type of product. But given the size of a potential space, the footprint configuration, using OSB to develop a rigid interior wall assembly not connected to the exterior in any fashion what so ever has been adopted in effort to have a fully decoupled mass/air/mass system. EDIT: Local code Matters Geography Matters I assume where the OP is, Tulsa, OK, that this type of construction technique would pass. But I am not an authority on code in Tulsa OK so it is on the OP to define or have defined for him that this is an acceptable practice. For instance, Stuart lives in Chile and that is an Earthquake prone area of the world. They build with concrete, so this practice would either require seismic stablizers or....concrete.

Stuart:

What type of "insulation" is that, shown in yellow?

It's R13 Fiberglass with vinyl backing. It is used as a vapor barrier to prevent condensation. I realize that I'll need additional insulation between the studs. I REALLY appreciate the helpful advice! Even though I feel like I've been drinking water from a fire hose, I know my studio will be better because of it. Brien: I'm with you now!

I'm just commenting to keep track of replies in this thread and to follow your progress. I had a lot of trouble figuring out how to beef up the outside walls of my tin shed and the diagram above is perfect!

Stuart, thank you for your patience.

. The optimum arrangement for a 3-leaf wall is where most of the mass is on the middle leaf (the middle leaf must have the same mass as the other two leaves combined)

In this scenario, I will have a double layer of 5/8" drywall on the middle leaf. So on the innermost leaf, I would need a single layer of 5/8" drywall. Correct?

In this scenario, I will have a double layer of 5/8" drywall on the middle leaf. So on the innermost leaf, I would need a single layer of 5/8" drywall. Correct?

Provided that your outer leaf has the same surface density as 5/8" drywall, and the two air gaps are the same size, and that you calculated your resonances and isolation correctly, .... then yes. BUT! : How did you calculate that you'd need that amount of mass on the middle leaf? And will you have the same amount of mass on the outer leaf as on the inner leaf? And what size will the gap between the outer and middle leaves be? And will that be the same size as the gap between the middle and inner leaves? Lots of questions! :) To be more clear: the optimum arrangement for a 3-leaf wall is where m1 + m3 = m2, where m1 is the mass of the outer leaf, m3 is the mass of the inner leaf, and m2 is the mass of the middle leaf, AND ALSO where d1 = d2, where d1 is the distance between the outer and middle leaves, and d2 is the distance between the middle and inner leaves. In that situation you get optimum performance, and then you can also use the simplified triple-leaf equations to calculate your MSMSM resonant frequencies, and your isolation. Of course, it is still possible to get good isolation with other arrangements of mass and air gaps, but then it becomes more complex to figure it all out. It would be nice if all this was easy to calculate, but the laws of acoustics don't want to cooperate with that! They like to be complicated, to maker our life more ... "interesting"... :) - Stuart -

If you do want to do the math to figure all this out, here's the equation for 2-leaf MSM resonance: And here's the equation for 3-leaf MSMSM resonance: - Stuart -

If you do want to do the math to figure all this out, here's the equation

Sorry but that is way above my head. I'm a humble mix engineer, not a rocket scientist.

Provided that your outer leaf has the same surface density as 5/8" drywall

I was assuming that you would remember the diagram I uploaded showing the metal siding/insulation as my outer leaf. So no, the outermost leaf (being 29 Guage metal) is not as dense as my innermost single layer 5/8" drywall.

How did you calculate that you'd need that amount of mass on the middle leaf?

Unfortunately my calculations are based primary on my limited budget and my cramped space that I am confined to. I know, I know....I can already hear the angry shouts of protest. :cop: In this scenario that I'm in, and assuming that the air gaps are the same, which option is the best choice for isolation: a) Metal Siding |air| (2) 5/8" drywall |air| (1) 5/8" drywall b) Metal Siding |air| (1) 5/8" drywall |air| (2) 5/8" drywall c) Metal Siding |air| (2) 5/8" drywall |air| (2) 5/8" drywall

Any comments on my last question?

In decreasing order of isolation (from best to worst), the order would be C, A, B. Of course, in all three cases I'm assuming that all of the air gaps are filled (or mostly filled) with some type of porous insulation: either fiberglass or mineral wool. But the basic question still remains: How much isolation do you need, in terms of decibels? Knowing the answer to that will reveal if any of those three are suitable, or overkill or "underkill". It might turn out that "B" is plenty good enough, or it also might turn out that even with "C" it won't be enough... So if you built "C" when "B" would have worked fine, then you wasted a lot of money. But if you built "B" to reduce costs when even "C" would not have been enough, then you still wasted money, since you built something that does not accomplish what you were hoping it would. Your biggest single unknown here is the most important of all: "How many decibels of isolation do you need?" - Stuart -

Of course, in all three cases I'm assuming that all of the air gaps are filled

The air gaps are purely air. See floor plan below:

But the basic question still remains: How much isolation do you need, in terms of decibels?

The painful truth is, that I don't know. :oops: I'll be primarily mixing pre-recorded tracks. I don't know how loud I run my monitors (Because of my new location, I have no studio to test my listening level). I've read that most engineers mix around 70 to 80 db. So I guess 80db would be an isolation figure to shoot for. As the above floor plan shows, I would like to go a double layer of 5/8" drywall on both leafs. I've also ordered green glue to help with the isolation. Another question. (thank you for your patience!!) Because of the small room size, should I go for a totally absorptive back wall? My only concern is killing too many high-end frequencies. And with an absorptive wall, can I place my double layer of 5/8" drywall in this configuration: Thanks for all your input. For the past two weeks, my life has been hanging on your posts! :lol:

The air gaps are purely air. See floor plan below:

If you do not put insulation in there, then you are sacrificing a huge amount of isolation. Anywhere between about 5 and 15 dB. On the other hand, you say it is only air but on the diagram it clearly says "R13 insulation between studs"! :?: It can't be both! So which is it? Do you have insulation in the air gap, or not? Leaving the air gap with no insulation at all greatly reduces isolation, so I'm hoping that the diagram is correct and there really is insulation in the air gap. Your diagram says that the air gap is only 1", but that's a really, really, REALLY bad idea. Especially so if there is no insulation in it. With only a 1" air gap, the MSM resonant frequency will be very high, without insulation it won't even be damped at all, and your isolation in the low end of the spectrum will be poor. The air gap should never be less than about 4", and should always be filled with insulation.

The painful truth is, that I don't know. :oops: I'll be primarily mixing pre-recorded tracks. I don't know how loud I run my monitors (Because of my new location, I have no studio to test my listening level). I've read that most engineers mix around 70 to 80 db.

But you also show a live room in that latest diagram? That implies tracking acoustic instruments at least occasionally, and they will very likely be much louder than 80 dB. Drums, for example, are typically around 110 to 115 dB.

I've read that most engineers mix around 70 to 80 db. So I guess 80db would be an isolation figure to shoot for.

:shock: :shock: :shock: That would be great, if it were possible, but I somehow doubt that you'll get 80 dB of isolation from that structure, and shooting for a goal of 0 dB outside is waaaaaay overkill! :!: :!: 0 dB is quieter than most anechoic chambers, and certainly fifty times quieter than you'll find in nature. Even standing in the middle of the desert at midnight with no wind and nobody else within miles, is way louder than 0 dB SPL. Your own breathing and heartbeat are much louder than that. About the quietest that most people will ever experience in their entire lives is around 20 dB. 30 dB is what most people would call "absolute silence" or "totally inaudible". Most noise regulations specify something around 35 to 40 dB, so there's not much point in trying to get quieter than that. You should probably set a more reasonable target for your isolation, based on how loud your loudest recording session is going to be inside the studio, and how quite your local municipal regulations require for it to be outside your studio.

Another question. (thank you for your patience!!) Because of the small room size, should I go for a totally absorptive back wall? My only concern is killing too many high-end frequencies. And with an absorptive wall, can I place my double layer of 5/8" drywall in this configuration:

You could do it that way, and an absorptive rear wall is generally a good idea in a control room, ... provided that the rest of the room is taken into account. The acoustic treatment in the room should be balanced properly, and it should all start with the "standard" geometry for the speakers and listening position, plus the "standard" basic treatment. That implies that the speakers should be set up in the correct position, aimed at the correct point, at the correct height and angles, and then there should be superchunk bass traps in the room corners, thick absorption on the first reflections points on the walls, a cloud on the ceiling, absorption between the speakers and the front wall, and a mostly absorptive rear wall. When all of that is in place, the room should be tests using REW, and the results of that analysis will show if additional treatment is needed.

Thanks for all your input

:thu: That's what we are here for! :) - Stuart -

On the other hand, you say it is only air but on the diagram it clearly says "R13 insulation between studs"!  It can't be both! So which is it?

Yes insulation is between the studs of each wall but the there is a 1" air gap between the walls. I'm confused why this diagram looks strange because an air gap is presumably between any decoupled wall system. For example the wall chart diagram I posted from Bob Gold's site shows all the leafs from STC 40 and up to have a visible gap between two stud walls.

But you also show a live room in that latest diagram?

Based on the audio work that I've done in the past, I don't see myself recording live audio very much. When that would happen, it would definitely be during the day time when my neighbors are all at work. The main concern for isolation is mixing late at night when the neighbor 100 feet away is trying to sleep.

shooting for a goal of 0 dB outside is waaaaaay overkill!

I'm sure hanging out with nuckle heads like me are a thrill.

About the quietest that most people will ever experience in their entire lives is around 20 dB. 30 dB is what most people would call "absolute silence" or "totally inaudible"

There's always something to learn in these forums. I obviously want as much isolation as possible but I am juggling that with my cramped space constraints. At this point, I'll go with the "C" option that I posted earlier. Based off this, how much isolation do you think I'll get out of this?

Yes insulation is between the studs of each wall but the there is a 1" air gap between the walls. I'm confused why this diagram looks strange because an air gap is presumably between any decoupled wall system.

Right, and the air gap ALWAYS contains insulation! As I said before, if you do not put insulation in the air gap, then you sacrifice as much as 16 dB of isolation. It's that simple. The insulation acts as damping on the many different types of resonance going on inside the air gap, so if there is no damping then by definition all of that resonance is transmitted across the gap to the leaf on the other side. In more "every-day" terms, the insulation in the air gap functions exactly like the shock absorbers in your car. You can leave out the shocks if you want, and the car will still run fine... it just won't be a very nice ride! :) Maybe you are getting confused about the terminology here, since it isn't too obvious the first time you come across it. The "air gap" inside an MSM wall is often also referred to as the "cavity", and means the entire distance between the faces of the two leaves. so if you could somehow shrink yourself down and get inside that gap with a tape measure, you would measure it from the surface of the hard solid mass that makes up the outer leaf, to the hard solid mass of the surface that makes up the inner leaf, regardless of any insulation that is in there. The insulation is mostly made up of air anyway, and that's the entire point. If you have a wall where the leaves are 5" apart (surface to surface across the gap), then you have a 5" air gap, and it will always be considered a 5" air gap even if there is insulation in there. If you put 1" of insulation in, then you still have a 5" air gap, and if you fill all 5 inches with insulation, even then you still have a 5" air gap. It doesn't matter if there is insulation or not, the fact remains that the air gap measures 5" across, between the surfaces of the leaves. That applies to any pair of leaves, even if the wall is a 2-leaf, 3-leaf, 4-leaf, 5-leaf or X-leaf. The air gap between any two adjacent leaves is always measured like this, regardless of whether or not it has insulation in it. This is totally different from the "gap" that you leave between the frames for the leaves: That's just a gap that you lay out with lines on the floor when you are installing the framing. It is NOT the same as the air gap, because the actual leaf mass could go on either side of the framing, and there might even be additional mass between the studs, so you cannot use the framing gap as an indicator of the size of the air gap. Those are two very different concepts that are often confused.

For example the wall chart diagram I posted from Bob Gold's site shows all the leafs from STC 40 and up to have a visible gap between two stud walls.

I think you mean "between two stud.framed leaves" not "between two stud walls". That's a different thing too! (Terminology....) But in any case, the "air gap" MUST be filled with insulation if you want good isolation. It's the cheapest way of greatly increasing isolation. This paper might be interesting for you: http://www.digistar.cl/sayers-forum/ins ... r_CH_1.pdf

Based on the audio work that I've done in the past, I don't see myself recording live audio very much. When that would happen, it would definitely be during the day time when my neighbors are all at work. The main concern for isolation is mixing late at night when the neighbor 100 feet away is trying to sleep.

OK, that makes sense. So it seems that typically you'll have levels around 80 to 90 dB inside, and you need to get those down below ambient levels outside, probably around 40 dB. So a very rough guesstimate is that you'll need around 45 to 50 dB of isolation.

At this point, I'll go with the "C" option that I posted earlier. Based off this, how much isolation do you think I'll get out of this?

Assuming that both of your air gaps are at least 4", and that they are both filled with insulation, then you should be getting around 50 dB of isolation there, perhaps a bit more (if you leave out the insulation, it would be around 35 dB). But that 50 dB estimate only applies to the walls: the way you are showing your doors right now won't get you to 50 dB. Perhaps 25 to 30 dB. If you want 50 dB isolation for the entire room, then you need two doors for each location, back-to-back, one attached to each leaf. In other words, the doors must be done the same as the walls: 2 leaves, separated by an air gap. If possible, you should also attach insulation to the doors so that when they are closed the air gap between them is filled with insulation. If that isn't possible, then the air gap between the doors needs to be 1.414 times bigger than the air gap between the walls, and the surface density of the doors needs to be 1.414 times higher than the surface density of the leaf it is in. The same applies to windows: If you want windows in your studio, then you need glass in BOTH leaves (one pane of glass in each leaf), and the glass must be 1.414 times heavier than the same area of wall, with a gap that is 1.414 times bigger than between the leaves themselves. Then there's also the HVAC system: to get 50 dB of isolation, the air ducts need to have silencer boxes on them. And finally the electrical system: You cannot cut any holes in the walls, so all of the outlets, switches and light fittings must be surface-mount, and all of the wiring must be done in the room (not in the wall cavity!). There can only be one single penetration of the wall, where the main power feed comes into the room. From there, everything is distributed using surface-mount ducts, boxes, outlets, switches and lights. - Stuart -

I have a question. Why are you building almost Square rooms and why if you have possibly a 10 or 12 foot ceiling height existing in the building do you not utilize more of that height?

Brien wrote:

Why are you building almost Square rooms

I'm using the #2 room ratio found in Rod Gervias' book. Height:1 Width:1.28 Length:1.54 He credits L. W. Sepmeyer with three different ratios and the #2 ratio is the one that best fits my space constraints.

Brien wrote:

and why if you have possibly a 10 or 12 foot ceiling height

I'm building the studio onto an existing garage (which has a 12 foot ceiling). BUT, the addition must have a minimum of 2/12 roof pitch, which reduces my overall wall height. Stuart: Thank you so much for your helpful advice! I always learn something new.

Stuart has been great since we are doing this build from the inside out. Another example of why the stickies should be adhered to.