John Sayers' Recording Studio Design Forum Archive

I'm in the final stages of a studio buildout. All walls are double stud, 25 gauge, 24" OC with double layer 5/8" per side with batt insulation. I'm struggling for the right plan with the ceiling in the drum room. The building is Cinder Block, I'm on the lowest floor on the poured concrete foundation and the ceiling is 8" precast concrete (I've acoustically caulked all of the joints between slabs and around the edges). The contractor is setup right now to do hat channel (25 gauge), resilient channel and then 2 layers of 5/8" rock, I'm planning to have him introduce Green Glue between the layers. The room in question is 16'wX22'lX9'h.

My hope is that no one working above will be aware of drums being played over the sound of day to day noise (outdoor factors, music, conversation, etc)-- I understand this is lofty Here are my questions:

1. Am I creating a triple leaf design by adding another cavity between the sheetrock and the spancrete, or do the cavities in the spancrete not apply to this theory?

2. Is the resilient channel counter-effective in this scenario even though the likelihood of short-circuiting is incredibly low (concrete instead of wood joists)? I'm concerned about Low Freq through the floor.

3. Dependant on answer to question #1, would RSIC-1 Clips or similar make a significant enough impact on the design to make it worth the cost? Would they be reliable fastened to a precast concrete ceiling? ie- Clips, Channel, Batt Ins, 5/8", GG, 5/8"

Thanks in advance for any responses, you all have been very helpful already.

Hi there "AerialView", and welcome!

I'm not quite sure what you are describing! In some places it sounds like a fully-coupled two-leaf ("All walls are double stud, 25 gauge, 24" OC with double layer 5/8" per side with batt insulation") which wouldn't be very good for isolation, but other places sound like the walls aren't built that way at all: ("The building is Cinder Block"), while yet other places sound like there is some attempt at partially decoupling something ("to do hat channel (25 gauge), resilient channel and then 2 layers of 5/8" rock")! So it's hard to understand what you really have there. Also, ith the latter comment, it isn't clear why you would have both hat channel AND resilient channel on the same wall. For what purpose?

Am I creating a triple leaf design by adding another cavity between the sheetrock and the spancrete

What spancrete? Where did that come from?

2. Is the resilient channel counter-effective in this scenario even though the likelihood of short-circuiting is incredibly low

Short-circuiting what to what? The purpose of resilient channel is not to prevent flanking (short-circuiting): it is meant to decouple the drywall from the studs, joists, trusses or whatever else it is attached to. If the inner-leaf drywall would otherwise be attached to something that is connected to the outer-leaf, then yes, you need the resilient channel. But from your description it isn't clear what is attached to what!

I'm concerned about Low Freq through the floor.

Why? How is that related to the drywall on the walls and ceiling? I don't see the connection. You said your floor is "poured concrete foundation", which I assumed to mean slab on grade. Is that not the case? Is there some type of crawl space below the floor slab? Another room down there? Is that why you are concerned about low frequency transmission through the floor?

3. Dependant on answer to question #1, would RSIC-1 Clips or similar make a significant enough impact on the design to make it worth the cost?

If you are already using resilient channel, then why would you also want RSIC clips? They both accomplish the same purpose, and you cannot even use resilient channel on RSIC clips. RSIC is meant to carry hat channel, not resilient channel, which is very different.

Would they be reliable fastened to a precast concrete ceiling?

You should probably take a close look at IR-586 to see why that would be a terrible idea. Putting drywall directly over a massive surface with only a very thin air gap is a really, really bad idea, even if you do use RSIC clips plus hat channel, or resilient channel. If you look at the graphs on page 8, you'll see that with this scenario, the entire low end of the spectrum has even WORSE isolation than for just bare concrete! In other words, doing what you propose (adding RSIC clips plus hat channel then drywall) directly on the ceiling surface, you would LOSE several dB of isolation for every single frequency below about 350 Hz. Meaning the entire low end of the spectrum, plus the first octave of the mid range. All of that would have worse isolation than if you did nothing.

If you look at the subsequent pages, you'll notice that there are many, many ways to get the same effect (reduced low frequency isolation) and very few ways to get an increase.

Please post some photos of what you actually have right now, and some accurate diagrams of what you plan to do, since it isn't clear what you have in mind, and if it is what it sounds like, then you'd be making things worse, not better.


- Stuart -

Hi Stuart, thank you for the welcome and the patient response. I can't find a live link to IR-586. I'm sure it's right under my nose but I can't find it with a search on this site or google to save my life.

I'm attaching a photo to clarify a few things- the Live Room is the room in question, but I will use the same treatment on the Drum Room (which is just a rehearsal space for a drummer) and the ISO room. Also to note, the "Utility Room" is a small edit suite as well, and that even if the diagram shows rooms walls coupling to another that each room in reality is autonomous.

The perimeter of the entire studio is Cinder Block walls, and this larger space is split into multiple rooms (control room, iso room, live room, etc), so any 'thick wall' you see in the diagram is a Cinder Block wall and any 'thin wall' is a stud wall.
-All perimeter walls of the entire space (from interior to exterior) are:
|| double 5/8" rock | stud wall with batt ins | inch air gap | cinder block ||
-All interior walls are:
|| double 5/8" rock | stud wall with batt ins | 1" air gap | stud wall with batt ins | double 5/8" rock ||
-You are correct, the floor is slab on grade. I was unclear and meant to say I am concerned about Low Frequency through the ceiling above me, the floor for the people above

Spancrete is the ceiling of the entire space, and will be left that way everywhere except for the Live Room, Drum Room and ISO room. Those ceilings are the only places where resilient channel, hat channel, clips or green glue are coming into question. The clips were suggested to replace the resilient channel, not add to it. I failed to mention that.

The first part of the question which I believe you were speaking to, was whether or not creating any kind of cavity beneath the spancrete (hat channel, clips, et al) would create a triple leaf design-- with the result of worse low frequency transmission. If I'm hearing you correctly in saying that is in case the fact and that creating any kind of cavity is a bad idea, what would you suggest? Is affixing a layer of sheetrock to the ceiling then using green glue to attach a second a possibility? Or is what I have what I get and anything I do will only affect it negatively?

Thanks again for your thoughtful response.

Pictures, pictures, pictures.....

Spancrete is an American company it is not a product so what you refer to can be an number of things in respect to precast concrete.

My assumption is that you have a typical precast hollowcore that is poured in a mold and prestressed and has "ports" that run from one end of the member to the other that help reduce weight and allow for electrical, plumbing,mechanical, what have you, to be feed thru.

I don't think you will create multiple airspaces but you will create a very small air space between the precast and the rc which can work against you and will also be a path for flanking to be introduced into the membrane/ceiling.

Let me ask you a different question. To what did you attache the framing when you had this thing built?

xSpace wrote: My assumption is that you have a typical precast hollowcore that is poured in a mold and prestressed and has "ports" that run from one end of the member to the other that help reduce weight and allow for electrical, plumbing,mechanical, what have you, to be feed thru.

You're dead on. 8" precast as I mentioned but yes, hollowcore with ports.

xSpace wrote: Let me ask you a different question. To what did you attache the framing when you had this thing built?

Attached on floor and ceiling. Pictures attached. Let me know if they fill in the blanks enough or if I should get specific pics of something tomorrow when I'm back over there. Thanks for weighing in xSpace!

Moving forward and trying to get definitive about whether or not this is triple leaf/problematic multiple cavities, let's assume that there will be no resilient channel. Starting point is clips, channel, 5/8 rock, GG, 5/8 rock.

If the gap from that combination is problematic at roughly 1 1/2", is there a depth at which it becomes helpful? What depth is that?

Any suggestions of the best way to treat this situation?

Actually you said this

Am I creating a triple leaf design by adding another cavity between the sheetrock and the spancrete, or do the cavities in the spancrete not apply to this theory?

Essentially this build is short circuiting. All hard connection points are fastened to the building/structure. Any vibration that happens to the structure will be passed directly into the new build via all the connection points and >vice versa<. So even if you did use RC and/or clips...doesn't matter.

Flanking cannot be eliminated and has to have strict attention paid to it to "break" the path that vibration travels on. There are no broken paths in this build it is a 4 lane freeway for vibration.

So you have a few things you want to consider. You could leave it as is, throw good money after bad, use greenglue on the sheetrock layers and maybe get something not as bad as it will be in the current form...no promises with no test data.

Or...you can knock it all down build with either wood framing and OSG sheathing to keep the walls vertical, build the new ceiling on the frame you develop on the new wood walls OR you can knock it all down and use structural steel studs, sway bracing, kinda the same thing only different.

Shoulda come by earlier

xSpace wrote:Actually you said this

Am I creating a triple leaf design by adding another cavity between the sheetrock and the spancrete, or do the cavities in the spancrete not apply to this theory?

You may not have seen my opening paragraph:

AerialView wrote:the ceiling is 8" precast concrete (I've acoustically caulked all of the joints between slabs and around the edges).

I recognize the inherent issues you mentioned. My current studio was built similarly but with a triple leaf design and is very usably isolated. Many of my friends are in similar building situations that still remain extremely isolated. I guess I'm looking for if anyone has knowledge about the original question as it stands now: What is the best way to attack the ceiling? Is it to leave it open?

This is just a follow up to anyone who may come across this thread in the future. I want to start by saying, if you haven't started yet, please follow the helpful advice of Brien and others and do yourself a big favor from the get go on your build. My experience was that I found this forum too late, and at that point wasn't able to find anyone willing to respond to the stage I found myself in. This is for the off chance of someone else wondering where it ended up.

I have been happily working at full capacity in my studio for nearly 2 years. In the end the contractor and I decided to do 2 runs of C channel/Hat Channel (perpendicular/criss crossed) attached to the ceiling. We attached resilient clips to the first run of channel and then of course hung the 2nd run of channel from the resilient clips. The resulting cavity was filled with mineral wool and was 3-4" deep if memory serves. I couldn't be further from officially advising anyone to adopt this into their building plan, but if you find yourself in a similar situation as I did this approach worked for us.

Whether or not this was the best option for where I was at I will never know, but I'm happy to say that I fairly regularly mix records while a full band rehearses in the live room. Once in a while the Ampeg 8X10 becomes noticeable, but even then it's never been what I would consider problematic.

All the best to you in your builds, especially if you're like me and more "production" than "engineering" minded by nature! We need all kinds.