ISOLATED ROOM-WITHIN-ROOM in NEW YORK, NY

That's a very interesting thought, Stuart, about hanging the ceiling as opposed to forcing our inner walls to bear the load. I will look into it. I thought people would find it useful to see what the structural engineer's letter looks like. I'm pasting it here and removing the identifying information. *** Name, P.E. of Engineering, P.C., performed an examination of the 1st floor and basement floor levels at said location, New York NY on the above indicated date. The existing 1st level floor consists of a flat arch terracotta flooring system with 8” deep steel beams spanning North/South at approximately 5ft on center. The steel beams are bearing into the exterior masonry wall at the North and into an intermediate interior masonry wall at the South (this still requires confirmation by gaining access through the basement interior door closed during the inspection). Upon inspection it was noticed that two of the 8” steel beams were extensively deteriorated at the bearing ends with the North wall due to continuous water leaks over of the years. The deterioration spalled the terracotta and exposed the beam. It is the P.E.'s recommendation that all the steel beams be exposed at their bearing ends along the North wall to verify extent of deterioration. Once deterioration of existing beams is determined, the capacity of the existing flooring structure can be evaluated. Extent of repairs and repair details can then be prepared by a NYS licensed professional engineer and filed with local authorities. Electrical, plumbing, hazardous material and building code aspects were excluded from the scope of this review. Other areas not specifically mentioned in this report were not included in this review. The various conditions noted in this report are as of the date of the inspection. P.E. takes no responsibility for the original design and construction of the structure or any portion thereof. Nothing in this review shall be constructed to represent a warranty or guarantee by P.E. of any work done, in progress, or to be performed by any contractor, maintenance entity, or others not in direct employ of P.E., in connection with this structure. By copy of this report, the Owner of this property is informed of these conditions. We will be glad to answer any questions you have regarding this project.

Ok, a succinct, discrete question in the midst of all this structural hoopla. As I described above, we have a probem regarding a duct chase that passes through our space from the west wall to the east wall. It is soffited to the ceiling (if that's a verb) and re-radiates a good deal of air-friction sound (I don't personally hear any buffeting, and the duct comes from the compressor five stories up on the roof). The duct feeds through to the next-door neighbors. I am concerned about reducing the re-radiated sound from the duct itself, and about transmission of our sound through the ducts to the next-door neighbor. However, I don't know if we have the right to modify the duct itself. Assuming I'm right about that, what's the best plan? I was thinking of removing the soffit and wrapping the duct in a fiberglass "duct lagging system" such as this: http://www.theproudfootcompany.com/Stores/Noisemaster/Industrial_Noise_Control/Pipe_and_Duct_Lagging/NM_LAG_2/#fragment-2 Then there's the question of whether or not I rebuild the soffit -- since I'm putting an isolated, single leaf ceiling below the duct, I imagine that rebuilding the soffit would create a triple-leaf (duct, soffit and inner ceiling). Does that sound right? The other option (I think) is to remove the existent duct and replace it with ducts that are lined in the interior with faced 703-type, then replace the hanging hardware with a resilient system for the length of our room. Finally, we would do some sort of treatment around the duct entry and exit openings. But I don't know whether such a thing is allowable when it involves a compressor on the roof that's not ours, and ventilation in the chinese restaurant that the duct runs to. Thoughts? Thanks all. Reed

I know Stuart mentioned that he might be out for a few days ... I'm just following along on your thread ... Wonder ... can you get some pictures posted here showing what you're dealing with ? Might help to get a better understanding.

Hi RJ, thanks. If you look at the photos of the space earlier in the thread, bottom of page 1, you'll see one facing the western wall where the duct chase is in the ceiling. It runs straight THROUGH our unit, but does not feed HVAC to our unit at all. However, the sound of the air rushing through the duct, added, I suppose, to the sound of it turning right angles outside our space, re-emits a reasonably loud whirring sound that has to be contained. Thanks for giving it some thought! R.

Ok, the landlord has opted to take care of the structural problems in the floor, and will reinforce it appropriately. We are moving ahead. Here are new photos of my sketch up doc. Unfortunately, the file is too large to post anymore. I'd like to know your thoughts, Stuart, as well as anyone else's who would like to chime in. In case you'd like to see the full file, here is a link for downloading. I know we're trying to keep things within posts, but this is just an appendix for further information: https://www.yousendit.com/download/QlVqTGt5Tk1EbUpjR01UQw As a side note: For the live room, I recommended using optimal ratios, but my friend insisted that he'd rather have as much space as possible. So that's what defines those dimensions. Between the two rooms I will use sliding glass doors. I managed to find a company that sells single-pane, laminated doors in pairs. I will hang 2 sheets of 5/8" drywall inside the frames, sandwiched together with Green Glue. The ceiling will be the same. The sole plates will be floated using Mason Industries neoprene partition supports. My questions are: 1) Do 2x6's make sense for this build? Or should I revert to 2x4's? 2) Does having them 16" OC make sense? On the one hand, I figure 16" is sturdier than 24". On the other hand, it's heavier, and I imagine those "cells" that get created between the 2x6's have a resonance of their own, and figure that gets worse as the spacing gets smaller. 3) Is the window, a 500 lb. laminated sheet of 5/8" safety glass, too big for this type of framing? Are there other ways of reinforcng the frame so as to account for the weight? 4) Should I be doing a let-in wood brace to prevent shearing or torquing? I would imagine I would do that with a 1"x6", from one corner to the other. Thank you Stuart, and everyone on this board! :D Best, Reed

If your floating the wall on isolation mounts, go with 2x6 on 24" centers and use 2x8 let-in minimally on the bottom. The 2x6 will be more rigid, the wider spacing better LF isolation, and roughly the same mass as the 2x4 on 16". Use blocking on the stud walls and ceiling. The big window may impact your isolation and treatment options. An angled wall to,divide the booth and CR may be a better choice.

Hey Glenn, thanks for your thoughts. And thank you for your advice on doing the 2x6's, but 24" oc. Somehow I had a suspicion that smaller spaces between studs must mean less transmission-loss ability of the structure -- it feels great to have that verified! And I will most certainly block, on your recommendation. Back to reading my Visual Framing book! What do you mean about doing a "2x8 let-in minimally at the bottom?" Does that mean only do a notch that's, say, 1/2 or 1" deep, not the full 1.5" of a 2x8? And what do you mean, only on the bottom? Not from upper left to lower right? Now about the angled wall -- I'm always scared about angling walls without using some one else's model. F. Alton Everest had a section about how it becomes so unpredictable, and I already have a 1:1.3:1.9 ratio going. What did you have in mind? What angle, and from where to where? I imagine you're thinking from southeast to northwest, right? Thanks very much for the help! I really appreciate it. Reed

Glenn, is this what you're talking about with a "slightly let-in" 2x8 brace? I did it 3/4" in, 3/4" out, and upper-left to lower-right corners -- I didn't quite get the "let in at the bottom" part. Am i getting it? Thanks. Reed

the let-in runs 90­° to the plate and is set 1 1/2" in (so fully). this ensures the load across the plate is better distributed if you use isolators on 4' centers (for example).

Aha! Now I think I've got it! Fascinating that that helps to average out the load. I wish there were a book that showed how the load gets borne throughout each stud and beam of a frame... Thanks Glenn. Reed

I wish there were a book that showed how the load gets borne throughout each stud and beam of a frame...

You can get some real pretty diagrams showing exactly that by using FEM/FEA software. Different colors show different levels of stress, and animation shows how that changes as the load conditions change... But that's not something that you can play around with yourself: you need a trained and experienced operator to do it for you. But it gives you great insight into how stresses and strains are distributed through a structural system, and how it will behave under load. I know a little about it, as my company used to sell that software, years back, and the guy I hired to demo the software could show you some pretty fascinating things. Anyway, that's a bit off topic. Sorry! :) - Stuart -

Hey Stuart, how are you!! Wow, that would be amazing to see! And quite confidence-boosting if the structure bore the load well. I YouTubed FEM/FEA and found some amazing demos -- mostly of cars crashing and whatnot, none on framing. But pretty darn cool. R.

Alas – Upon further consultation, it has become clear that we need to wade our way through the NYC permit system with the Department of Buildings. This will take many moons. I will post again when we have a sense of when we can begin; but for the time being, the project is in cryogenic freeze. Thanks all – R.

In the meantime re-read Rod Gervais' book which you mentioned you had. I thought he covered the topic of stress loads on frame walls fairly good.

Hmmmm.... Not sure where you're finding it. It's a phenomenal book, but it doesn't cover (or try to cover) the issues that were giving me trouble: 1) whether a window's weight becomes untenable once it reaches a certain percentage of the wall-frame 2) what the actual calculations would be to decide between 2x4 vs. 2x6, and between 24" OC vs. 16" OC 3) how bracing and blocking work to distribute the load, and at what weight-per-length they become crucial. Do we have different editions? R.

I have the second Edition. Don't have it hand right now but I seem to think it was rather later in the book. You could question him directly at his email address which he gives in the book or you might try posting on the "questions for Rod Gervais" thread in the acoustics forum over at Gearslutz.

Wow, there's a "questions for Rod Gervais thread"... I had no idea. I'll go check that out. Thanks Brian! R.

http://www.gearslutz.com/board/studio-building-acoustics/333500-questions-rod-gervais-about-his-book-build-like-pros.html There is also the Studio Construction Forum at Recording.Org where Rod is in fact a Moderator http://recording.org/studio-construction-and-acoustics-forum/

Well, a cryogenic freeze is a faster state than I would have thought. We have an architect who knows the NYC permitting world well helping us through, and we met at the space a couple days ago to go over my design. The first major change is that we'll be required to use steel studs instead of wood -- which may make my Sketchup models less pretty, but will save us a ton of weight. Well, I shouldn't casually say a ton -- but it sounds like it'll save us about a third. Sweet! :yahoo: It'll also cost a bit more... but that doesn't seem to be a major concern, so I'll go with it! Q: Are there any acoustic consequences of using steel framing instead of lumber framing that I should be aware of? Back in the game! R.

Q: Are there any acoustic consequences of using steel framing instead of lumber framing that I should be aware of?

Actually, it's the other way around! You get a slight benefit from metal framing, not a penalty, if I recall correctly. I'd have to check to make sure, but I do seem to recall that there is a small advantage to metal studs. - Stuart -

Well that would be exciting! So aside from the beauty if you're doing inside-out construction, and the 15% savings in cost, I guess lumber has no advantages over steel for studio construction. Then there's also the fact that lumber "settles" as it ages and dries, which I hear can lead to problems down the road... Anyway, happy I'm going with Steel. Thanks guys! R.

Meanwhile, I think I understand your suggestion of the "faux float" floor decoupling idea, Stuart. I've found some similar designs elsewhere. If this is correct: 4" 703 directly on concrete floor 3/4" plywood, grain width-wise Green Glue 3/4" plywood, grain length-wise. My real question is: does anyone have a number for the TL of this floor construction? I want to make sure it can keep up with my wall and ceiling design. Thanks everyone! R.

4" 703 directly on concrete floor 3/4" plywood, grain width-wise Green Glue 3/4" plywood, grain length-wise.

Yup! That's about it.

My real question is: does anyone have a number for the TL of this floor construction? I want to make sure it can keep up with my wall and ceiling design.

Well, it decouples more than isolates. It is more intended for impact noise, rather than as a true isolation floor. That said, it will isolate to a certain extent, but not easy to predict how much, since the "spring" here is partly air and partly 703. I don't have any resilience figures for 703 used as a spring. But at a very rough "guesstimate", I would suspect that the combination of a 4" concrete slab plus the above would give you a TL of maybe 50-something. That assumes that the deck is carefully sealed all around the edges, of course, so that it is airtight underneath. In other words, leave a small gap all around the edges and fill it with very flexible expansion compound, or backer rod and caulk, or something that will keep a good seal even with movement of the deck. - Stuart -

Hi all, Work continues on the design. I am still wrestling with what to do about the neighbor's duct chase in the middle of the outer shell's ceiling, and the great amount of height that rises on either side of it. Duck it like in this architectural drawing? Or simply make a flat ceiling to the lower height that the duct chase defines? And if so, what do I do within that huge airgap? -- I wonder what thoughts people have. Below is an architectural rendition of the Control Room elevation from the east (side view), as the design stands. I am striving for a 1 : 1.3 : 1.9 room dimension ratio (one of the ratios recommended by F. Alton Everest). The width of the Control Room's inner dimension is 148.5" maximum. That would make an inner shell length of 216", and an inner shell height of 114". The actual height of the bottom of the duct's outer shell is 119.5". The full height of the outer-shell space to either side of the duct chase is 147" -- a difference of 27.5"!!! If I simply design to the ratio's limit of 114", what do I do with all that extra space above the ceiling? My current plan leaves a great deal of empty space between the inner shell of the ceiling and the inside of the outer shell, for the rest of the room NOT underneath the duct chase. I have planned to just fill that interstitial space with standard R13 fiberglass batting. Is there a more efficient use of that space? Would a hanger system ABOVE the inner shell work, or does that only work if it's INSIDE the inner shell (behind a false ceiling)? I consulted with Rod Gervais about his hidden bass trapping design, ambitiously creating an OC 703/R13 bass trap above the space, but of course that too needs to be within the proper limits of the inner shell (http://recording.org/studio-construction-and-acoustics-forum/53153-question-rod-about-hidden-bass-traps.html). OR: Should I just raise the inner ceiling, even though it takes us out of spec with my chosen ratio, in order to take best advantage of the space we have? :? P.S.: Due to New York City's building codes, we cannot make a two-leaf system by stripping the inner layer of drywall on the ceiling and still maintain the required tenant fire separation. So after some consultations off-line with members, I've been advised to go with a three-leaf system and add 3 layers of ⅝" Type X drywall to the existing outer shell as a super-massy middle leaf.

Thought anyone? :D Thanks as always — Reed