Hi there "MrWaj", and Welcome to the forum!
Wow! You certainly do have a challenging situation to deal with. Fortunately, the same procedure that works for any studio build, will also work for yours... it will just be a bit more complex in the design stage.
So, first order of business: Put a number to your most basic need. Start with that, and the rest follows, and flows.
In other words, you need to actually measure / calculate / estimate the real number of decibels of isolation that you will need. It's fine to say " this design has to be super tight. Plus my studio engineer is a mad drummer", but there's nothing in there that you can plug into the equations for isolation, to figure out how to build your walls. You need a real number, that realistically represents the amount of isolation that you need, in decibels. So you will need a proper hand-held sound level meter (not an app on your iPhone!), and also a copy of your local municipal noise regulations. With your sound level meter ("SLM"), measure the level put out by your " mad drummer", when he's doing his best to wake the dead. That answers the first question that you need a number for: "How loud am I?". Do the measurement with your meter set to use "C" weighting and "Slow" response. Measure in several places around him, at a distance of between 1 and 2m. Note the highest level, and also the average level.
Now tell him to stop playing, send him home, and wait for the quietest time of night, then measure again with your SLM, same settings, when it's very quiet at the place where the studio will be built. That partially answers the second question: "How quiet do I need to be?". And the final double-check for that second question, is to look it up in your noise regulations, ad see what the LEGAL requirement is: The number that you cannot exceed. Compare that with your own measured second number: use the lower of the two numbers as your final answer. In other words, if you measured 35 dB with your meter for the quietest moment, but the regulations say you must stay below 40, then the number you want is 35. But if you measured 50 and the regulations say you must stay below 45, then the number you want is 45.
Ok, so now you have two numbers: the "How Loud" number, and the "How Quiet" number. Subtract. The result is the answer to the key most important question about starting your entire studio build. It answers the question "How much isolation do I need?". It puts a realistic, valid, objective number in place as the goal for your isolation.
Now you can start thinking about your design process. It was impossible to think about that before, because you did not know what your goal was, but now you do. Before, it was sort of like you deciding to go on vacation, and then you asked other people how to get there, what to do when you got there, what clothes to take, etc.... but you did not tell them where you wanted to
go on your vacation! It was impossible to answer your questions, because you dd not have a goal. You just sort of imagined yourself going on vacation, and buying plane tickets, and sleeping in a hotel, renting a car, etc., and you were asking about those things, but nobody could help you, because even YOU did not know where you were going! How can you buy a plane ticket, if you don't know where you need to fly to? How can you book a hotel, if you don't know what city to book it in? How can you isolate a studio, if you don't know how much isolation you need?
With your goal number in hand, you can then look at various construction methods that are capable of achieving that goal, and compare them to what you already have, to see if it is possible to get where you want to go, with what you have on hand. It might not be. It might turn out that there is no feasible way to use what you have to achieve the isolation you want. That's a real possibility. It would be a sad outcome, but at least you would KNOW that it was not possible, and you'd have to go looking for another place.
Or it might turn out that there are a few ways to do what you want with what you have. That is also feasible. In which case, you get to choose which of them makes the most sense for you, and for your budget.
So, I can't really answer most of your questions with concrete answers, because neither you nor I know what we are trying to accomplish here. All I can offer is general comments regarding where you are, and roughly, approximately, ball-park, guesstimating, more or less, possibly where I imagine I think you might maybe be going....!
Firstly, I'm assuming that you need high isolation, maybe around 60 dB, based on what you mentioned about a mad drummer and sound carrying over the pond.
Secondly, I'm assuming that you have a large budget, because if you don't, I can already tell you that you can't get where you say you want to go, because of the first assumption: you can't get high isolation on a shoe-string budget.
OK, so with those tow basic assumptions, lets look at what you have:
walls consist of one layer of 1/2" OSB / 3 1/2" of polystyrene foam / one layer of 1/2" OSB all glued together.
Not very hopeful as the basis for a building that must provide high isolation. SIP's are not much good at that. (SIP = Structural Insulated Panel). They are pretty good for thermal insulation, but not so good for acoustic isolation of loud sounds. There's a fair amount of research on this, and it' is not very heartening. For example, this is what it says in a study on using SIPs for new houses near a road: "
Sound transmission loss testing of standard SIPs, however, reveals relatively low acoustical performance especially in the 630 Hz range. This characteristic acted as a band pass filter allowing a portion of broadband noise to enter the house." If there's an isolation dip way up high in the spectrum at 630 Hz, then that automatically implies that the panel is pretty lousy at acoustic isolation across the entire spectrum below about 1 kHz at least, and probably more like 2 kHz.
And in a technical bulletin about SIPs in the UK, they had this to say about the acoustic properties: "
A SIP, much like timber studwork, relies on the mass and continuity of plasterboard linings to provide the majority of the sound insulation performance. If the sound insulation performance of the wall needs to be improved, the use of acoustic rated plasterboard in multiple layers is normal. An acoustic consultant would need to be involved to determine specification and performance requirements." Translation: SIPs are really lousy at isolating sound, and you need to add many layers of high mass materials to get the performance up to scratch. On a manufacture's website FAQ, they have this to say about how well SIPs work: "
...low frequency sounds are not effectively stopped by a SIP building envelope.".
I think you are getting the picture: your SIP walls are not doing you an favors, and you are going to need to add some major mass to them, if you need good isolation.
Here's a real graph, showing how a SIP wall compares to a standard stud wall:
SIP-acosutic-properties-polystyrene-insulated-panels-OSB-TL-graph-STC.jpg
Not a very happy sight. It gets 7 points LESS isolation tha¿n an ordinary stud wall, which is already pretty poor. And do note that this test was done with a layer of drywall already applied to the SIP! Imagine what the sip would be like, all by itself....
So you are starting from a highly disadvantageous point, and you need high isolation... Take another look at my second assumption...
My intended solution is to hang RC on the existing walls of the building, sheath that and then build a floating wall inside of that and sheath that. I would end up with.....
You would end up with a three-leaf system!
And a three-leaf system will perform WORSE than the equivalent two-leaf system. If you really do want to build a 3-leaf wall, you will need to compensate for the isolation that you are losing by building 3-leaf. It would be far better to build a 2-leaf wall, which is the optimum configuration for any give isolation need (lowest cost, lowest mass, lowest thickness). I'm not saying that you can't do a 3-leaf system: you can if you want, but it will cost you more, use more materials, and more space. And since your plan has two of the leaves very close, with a very thin air gap between them, you'll need to do some rather major compensation to overcome that....
Second challenge is the garage doors that have to stay in place. I was just going to remove the tracks, frame a stud wall inside the doors in contact with the floor and roof system and treat framed wall the same as the building structure walls.
Correct! That's the best way of dealing with they typical garage door issue, where the door has to remain physically. Fox the door permanetly in place, remove the hardware, and build a wall in front if it. Yes, it does create a three-leaf system in that part of the building, but you have no choice. And since it is a simple stud wall, it is easy to compensate.
The garage has a 10" hollow core pre stressed concrete floor with a 2" concrete topping over a concrete basement with 9' ceiling.
What's down in the basement? Anybody down there? Could YOU go down there? That basement would likely be a better candidate for a studio that needs very high isolation. So if nobody is using it right now, I would suggest that you consider moving your studio down there.
I know I'm creating a drum but tests so far seem to hint that it should not be a problem.
How did you test that? What numbers did you get? What is the frequency that gives you the least isolation for airborne sound transmission, how much isolation did you get at that frequency? What was the level of impact noise isolation that you measured?
Sound traveling through the floor to the outer shell of the building?
If sound is getting into your floor, then it is ALREADY in the shell of the build, regardless of the basement. That's why the IIC test results are so important. If you can show what you got there, then that would help. A simple solution might be a drum riser and bass cab isolation pad. If not, then your only solution is a PROPERLY floated floor, and we get back to my original second assumption: you have an abundant budget. You'll need a large budget if you have to float your floor.
Fourth is the ceiling. Not really problem just a question.
Why is the ceiling "not really a problem"? That's strange: normally, in a typical garage isolation scenario, the ceiling is a MAJOR problem. I'm wondering why you think yours will not be.
Which is better, three layers on 5/8" on RC or hung on a floating frame attached to the roof with isolators?
When you go on vacation, which is better: The road that goes the other way, or the river that goes in a different direction?
There's no way to answer your question, because nobody knows what your goal is, or any of the other details that would be needed to come up with a valid answer. The ONLY answer I can give you here, is that the best ceiling system for high isolation in general, is a fully decoupled two-leaf system where the total mass is split evenly between the two leaves, there is enough surface density on each leaf and enough damped air gap between them to produce an MSM resonant frequency that is at least one octave lower than the lowest frequency that must be isolated, and sufficient overall mass to satisfy the Mass Law parts of the remaining 2-leaf MSM equations. I can't be more specific than that, since there is not enough information to go on. Not even to hazard a wild guess. Another way of looking at it: the inner-leaf of the ceiling must have the same mass as the inner-leaf of the walls, the outer leaf of the ceiling (roof?) must have the same mass as the outer leaf of the walls, and the air gap in the ceiling must be at least as large as the air gap in walls, and damped to at least the same level.
Fifth is that we are trying to keep the three approx. one square meter windows looking out over the pond
"If you like your windows, you can keep your windows"!
On a more serious note, there's no problem with having glass in studios. Glass is very dense, rigid, and slates well... if used correctly.
Current ideas is two layers of glass, one 1" (I own this currently) and one layer of 1/2" laminated separated by a 4" to 5" air space.
Did you do the math? Does that produce the level of isolation that you need at the frequencies where you need it?
Additionally removable panels for heavy drumming and bass playing.
Why? How would those work? Why would you need them? I'm not sure I understand what you are trying to achieve here, or how that would work in practice. Please explain.
prepping for construction, hopefully next week.
WHAAAA?????
No. Just no. BIG no. HUGE NO! You are about a YEAR away from being able to build anything. And I'm being realistic. You don't have any plan at all, you don't know hoe much isolation you need, you don't know what construction materials you need, you don't know how to put them together, you don't have a structural plan, you don't even know what your legal requirements are, and I'm betting that you don't yet even have a building permit....
I've designed quite a few studios over the years, and I've been involved in one way or another with the construction of many, many others, both on the forum and off it. I don't want to seem harsh, or condescending, and I'm not trying to belittle you, but one thing I can grantee, without any hesitation: if you start building before you are ready, with a fully detailed plan in place, you are doomed to fail. I've seen it so many times, and it is always sad. We occasionally do get people coming on the board like this, without the slightest plan and saying they are going to start building next week, but the questions they ask reveal that they are nowhere near being ready to even THINK about starting. We always tell them the same thing: "STOP! Don't do it!". The ones who listen, generally go on to build spectacular studios. The ones who DON'T listen, think they know better, and carry on building anyway, always fail. Every. Single. Time. We know that they fail, because their threads always dry up after a short while... and you can be sure that if they DID succeed, they'd be back in our faces, rubbing our noses in their success, and showing that we were so very wrong by showing the wonderful results they got from their studios... but that has NEVER happened. Not even once. Those studios either never get finished, or they do get "finished" but turn out to be so lousy that nobody would ever consider using them.
I'm hoping that you are one of those guys who will be the first type: That you really will stop, and listen, then take the time to learn everything you need to know in order to design your place, then design it comepltely, in full details, then get the necessary red tape out the way, and only then think about starting to build.
So you have a choice here: you can start building in January 2018 and fail, or you can start building in January 201
9 and succeed. If all goes well, and your needs are not too complicated, you might even be able to shave several months of that and still succeed. But if you start in January 2018, I'd bet really good money that you will not succeed at all.
Please tell me that you are the first type of studio builder: the one one who came here to listen, and learn how to do it right, and take the necessary time!
Merry Christmas!
- Stuart -
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