Detailed drawings and assembly questions

Hello- Like many around here, I've read, lurked and dreamed here for a long time, but I am finally ready to build my basement recording studio in Northern California. I am hoping that the attached detailed drawings can be a help to the folks here. Here's the situation: The existing conditions: a primarily sub-grade garage space contained by 8" thick concrete walls, a 5" concrete slab on grade, all 10 year old good quality construction. It sits directly below living space. The project: Build a reasonably soundproof personal recording/limited rehearsal space within a family home I *think* I have a fair amount worked out but here are my questions: 1. In wall section A, the ceiling assembly does not add new mass at the subfloor level, while wall section B adds 2 layers of 5/8" GWB at the subfloor. Obviously, B is a lot more work - is it worth it/necessary in an application like mine? 2. In wall section A, the floor assembly of hardwood flooring/subfloor sits on 1/2" neoprene pucks, while in wall section B the hardwood floor/subfloor are placed directly on a vapor barrier on the slab (which is pretty much level). Do I need the neoprene? Are there any issues with placing the ply directly on the vapor barrier? Thanks again for everyone's help and advice. JP

To me it looks like both "A" and "B" show direct flanking paths from your inner-leaf ceiling to the outer-leaf wall. You will need to fix that.

Obviously, B is a lot more work - is it worth it/necessary in an application like mine?

Application like what? You didn't mention what you plan to do in that room, how loud it will be, or how quite it needs to be, or how much isolation you are already getting (all in terms of dB, measured on a meter). Without that, no-one can say if it is "enough" or not. If that's going to be your won individual harmonica practice room, then all that extra work is not necessary in the least. But if the room is intended for a full heavy-metal rock band with a trained gorilla pounding a major drum kit, a gazillion watt bass guitar cab and a bunch of electric guitars to match, then even that extra effort won't do the job!

the floor assembly of hardwood flooring/subfloor sits on 1/2" neoprene pucks,

That might not be such a good idea! I reckon you'd be making a nice ringing drum head for your floor: A thin wood shell over a thin cavity with no damping at all, is probably going to ring very nicely, I would say. Your floor will happily hum the tune for you, right along with the rest of the band... Is there any reason why you can't just use the concrete floor as is? Or if you don't like concrete, then how about laying laminate floor?

Are there any issues with placing the ply directly on the vapor barrier?

What does your building code say? Is that allowable? Are other houses done like that in your area? Is the concrete always dry at present? If you tape a piece of plastic over the concrete for 24 hours, do you get moisture appearing under it? Maybe Rod will see this, and tell you for sure if that's a good idea or not: he's the expert on that kind of thing. One other thing: If you need really good isolation, why don't you do a full "room-in-a-room" build, so that you can rest your new inner-leaf ceiling on your new inner-leaf walls? If you do it using Rod's technique, then you won't lose much ceiling height at all, and the isolation will be better than from just using RC. IMHO - Stuart -

Thanks for the response, Soundman. The studio will be used for individual recording of vocals, acoustic guitar, some louder guitar amps, and occasional drums. Musically, think Beatle-esque pop, not metal. Occasionally, I'll have a 3 piece band rehearse there. The isolation need not be perfect in terms of flanking - the only adjacent space is the garage, but I'd like to limit too much bleed. I think if I can get to STC 63 with a double wall/double 5/8 assembly, I'll be fine. I would like to limit the sound pentration to the living spaces ABOVE though. If I went with the neoprene pucks, I am aware that I'd have to pack it with rockwool or 703, but given my slab on grade, it is probably not worth the time and money. Because the concrete is a bit unfinished feeling, aesthetically, I will likely put the laminate/Pergo/engineered floor over a vapor barrier and call it a day. Can you let me know where you see the flanking issues with the ceiling assembly and how you might correct them? I have pretty limited ceiling height (7'-8"), so I can't do Rod's room in a room solution. Thanks for your help. JP

Hi JP. Here is what I mean about the flanking. It is circled in red: The inner-leaf ceiling is directly attached to the outer-leaf wall through the framing that you show there. The inner-leaf ceiling should end where it meets the inner-leaf wall.

I have pretty limited ceiling height (7'-8"), so I can't do Rod's room in a room solution.

You already ARE doing a room in a room! You just aren't doing it very efficiently. Look at page 77 of Rod's book to see what I'm suggesting. That isn't exactly your situation, but the same idea will work, and will NOT cost you much more in height than you already are losing with the way you propose, using RC. If you build carefully, you could probably get to more or less the same height.

The isolation need not be perfect in terms of flanking - the only adjacent space is the garage,

Actually, that isn't entirely correct. The space "adjacent" to your room is really the rest of the house: isolation is an "all or nothing" proposition, and has to be done to the same level in all directions around your room, regardless of which direction is the most critical. Low frequency waves are not directional, and will simple wrap around your construction to the rest of the house, if there are any weak points.

The isolation need not be perfect in terms of flanking - ... I think if I can get to STC 63

If you have a flanking issue, then you will NEVER get STC-63 :shock: You'd be lucky to get anything much over STC-40, I reckon. Good isolation demands total decoupling. If you don't decouple, you just can't get there.

I would like to limit the sound pentration to the living spaces ABOVE though.

OK, so whatever isolation level you need in THAT specific direction is the level that you need for ALL directions. All of your walls, doors, windows, ceilings, electrical and HVAC work must be designed to give you the same level of isolation that you need going UP. Have you measured how much isolation you already have going up there, and how much more you are going to need? Without getting those real numbers, you can't know how to design the isolation properly. Guessing is not a good idea! :)

... and occasional drums.

So that answers the basic question: how loud are you? Drums = loud = up to around 115 dB peak. So you now have one real number to work with. Next question: "How quiet does it have to be up there, in order that marital bliss is not destroyed?" You need to measure that too. Guessing here could be even worse... When you have that number, subtract B from A, and you will get your answer to the biggest question of all: "How much isolation do I need?". Simple! Your equation will be "115 - (how quite I need to be upstairs) = (how much isolation I need)". Based on that you can start designing a structure that will give you what you need.

I think if I can get to STC 63 with a double wall/double 5/8 assembly, I'll be fine.

Unfortunately, "thinking you'll be fine" kind of sounds like guessing, doesn't it? :) You might well be fine with STC-63, but you'll never know for sure unless you run the numbers. And in any case, STC isn't a useful measure of isolation for music, especially things like drums and bass, since it does not consider the low end of the spectrum at all.

If I went with the neoprene pucks, I am aware that I'd have to pack it with rockwool or 703,

That still wouldn't solve the problem: it would just decrease the Q of the relevant resonant tones, meaning that you'd now have lower levels of resonance, but across more frequencies... :)

Because the concrete is a bit unfinished feeling, aesthetically,

Have you considered staining it? Search the forum, and you'll find several stunning examples of amazing things people have done with their concrete floors, just with plain old staining. You need every last micron of height you can get in that room, so I'm trying to give you options to minimize lost headroom. Other "thin" options are ceramic tile, laminate flooring, and even linoleum. - Stuart -