John Sayers' Recording Studio Design Forum

Ok, Stuart, I'm re-reading your most recent post and answering some of my own questions. Sorry for having been redundant/erroneous in my replies -- I was so excited that I spoke before I considered. But I'll leave it up; that way it will be helpful for others to see the learning process.

Sounds like I got good news yesterday, but not a solution to all my problems. 10.5" of concrete is a good start, but probably still a source of hard flanking from/to the neighbors, and to the rest of this city (at least at low frequencies). Therefore, I gather that my slab can't be the real studio floor-surface -- it's the basis for building the surface.

That brings me to the question about whether to do this right, and pour a new concrete slab as my second leaf. BUT: my friend does not have a month to wait for a new slab to cure! That may rule this strategy out, unless there are alternative compounds to concrete. Quikrete 5000? Sand-filled wood deck? Or am I just asking the impossible?

If I'm understanding it all correctly, then I DO still have to bring in a structural engineer, because I may need to reinforce that existent 10.5" concrete (I suppose with jacks). Where and how many must be a job for someone who has letters after their name.

Furthermore, I must now finish my design to determine the total weight of the two rooms, including HVAC and two new floor platforms (one for live room, one for control room). THEN I need to find/establish a spring system that will properly deflect that weight and all mechanical coupling (if I'm using "deflect" properly.) What I mean is: the springs need to be in the neighborhood of half-way compressed. Ok. Where's that bus you were talking about?

I suppose my real question is whether this is all doable for $20k. Or less, in which case I get extra points! But it sounds like this is gonna be more than a quick email-and-response with a structural engineer, so we're talking about a very real consultation, with at least several hours spent. I have no basis for knowing how many hours is reasonable to assume. I have one recommended structural engineer in the city, but he has no particular expertise in studios -- that may not matter. Or it may?

If I simply don't have the budget for that, I may indeed have to go with the "faux floating" idea you suggested, and just hope for the best.

Ok, gonna bang out the rest of this plan and see where it gets me. Just wanted to cover for my careless errors in my posts.

Reed

With a 10.5" reinforced concrete slab, you may or may not need to float your floor. That's the good news: you might NOT need to float it. The bad news, is "How in heck do I figure out if I need to or not??".

Starting with first things first: I'm not a structural engineer!! So take everything I say with a very large pinch of salt, and get it checked out by someone who actually is a qualified structural engineer, and who physically goes to your place, and who examines what you have, and who knows your building codes, and who gives it to you in writing, with his signature on it! Don't listen to me: listen to him.

Having said that, a slab such as you describe should have no problem supporting a lot of weight, if it is well built with good quality materials and the span is short. So you'd probably be fine building your entire studio on that, assuming you don't need to float the whole thing, and even then it might be good enough. But once again, there are a whole bunch of "if's" in there: Is there rebar in that slab? If so, what size? What is the strength of the concrete? What is the span? Is it ribbed? One way or two way? Any penetrations? What is the dead load? What is the design live load? What about the footings? How good was the party the night before the slab crew poured that slab? Etc. So I'm enthusiastic about your slab, and hopeful that you can do what you want on top of it without needing to spend millions. I think you in a good position. I was expecting that you'd say it is a wooden floor on 2x12 joists 24" OC, or something terrible like that, but you came up with pretty darn good news, so it seems you are OK there. But once again, yes, you do need a guy with some letters after his name to go in, take a look, measure, test, maybe even drill holes, then give you a piece of paper with his signature and his credentials on it, stating exactly what you can and cannot do. Since you live in NY, and NY is sort of known for its ferocious, rabid, feral, man-eating lawyers that would happily sue you if you even thought about regulations incorrectly, you most definitely need some guy with the right qualifications to put his professional reputation and legal liability on the bottom of that piece of paper.

Depends on the springs. For acoustic work, it usually includes some type of rubber or elastomer to deal with the high frequencies, as well as the "bit of coiled steel" that deals with the lows. Here's what the ones from Galaxy look like:

(Copyright Info: As far as I know, this photo is from Eric Desart, and was originally posted on StudioTips forum. But I may be wrong on that)

OK, so that's a bit extreme!!!! Galaxy is arguably the best isolated studio on the planet, and an article in a magazine a few years back says this about those monster springs:

"Desart devised a plan in which large helical springs, each capable of supporting 3.1 tons of load and with a resonance of 3 Hz, would be grouped and placed under the floor slabs of all of the studios and control rooms, which would in turn be isolated from each other via individual slabs and designed as free-standing concrete structures, which Van Baelen refers to as "bunkers." For example, control rooms one, two and three weigh 252 tons each, and each has 78 springs supporting it. Vermeir calculated a compression of the spring of 25 millimeters initially, with another 2 mm of compression over the next 30 years from mathematically predictable metal fatigue-more than a lifetime for most recording studio enterprises.

"A helical steel spring has the advantage of higher insulation values than viscous elastic materials, but at the same time the disadvantage of extreme[ly] low internal damping," Vermeir writes in an analysis of his recommendations. "Therefore, on the top and bottom of every spring package, an elastomer layer takes care of the natural frequency of the steel springs as well as the insulation of the high[er] frequencies." The total weight these springs hold at Galaxy is a mind-boggling 2,030 tons-more than 4 million pounds-including concrete and equipment, ..."
http://mixonline.com/mag/audio_galaxy_studios_belgium/

So that's sort of the concept, but yours would be just a tad smaller than that! !! (And a tad less expensive).

Here's what yours might look like:




Or WORST case:




You might find this publication useful:

http://www.acoustiquepn.ca/PDF/acs102v2.pdf


It would help if he's dealt with springs, but the main issue isn't the floated part of the floor: the spring manufacturer can tell you how to do that (and probably for free if you buy their springs!) The bigger issue is the structural integrity of the underlying original 10.5" floor. The question is: "Can that floor alone handle a floated floor on top of it?". But you only need to get to THAT question if you answer "yes" to the even more basic question: "Do you NEED a floating floor?". as far as the structural engineer is concerned, he just wants to know how much load you intend putting on that floor, and where you intend putting it. It's one thing to put a load of five tons spread evenly across the entire floor, hundreds of square feet, and an entirely different thing to concentrate that entire five-ton load over an area of just a couple of square feet. Those are two different things, as far as the floor is concerned. But the same things as far as the footers and foundations are concerned. It's complex. That's why you need a pro, not me, to tell you about that.

I'd really try to get a feel for how much of a flanking problem you have with that floor, and how much isolation you need, in total. For example, if you rest your fingers lightly on the surface of the concrete, can you feel vibrations in it as trucks drive past / planes fly over / you play loud, bass-heavy music on a speaker resting on the floor / people walk on the floor nearby / you tap on the floor with something solid. Etc. If you put your ear close to the concrete, can you HEAR sound coming out of it, such as things happening in other parts of the building, or out in the street? If you hear nothing, and only notice vibration when a dozen Sumo wrestlers jump up and down on the floor while wearing clogs, then you are fine! ( ). But if you can feel noticeable vibration all the time, just from ordinary street/building noise, well, then you are not so fine. That's not a very scientific, objective way of figuring it out, but it helps to give you a sense of how bad the problem might be.

But the key point here is to put a number to the question "How much isolation do I need?", in terms of decibels. If you can get a number for that, then it would help you decide on all the other factors, such as how to build your walls, ceilings, HVAC, doors, windows, etc., which in turn dictates the mass of everything, which you will need to know when the engineer comes round to take a look. It's no use calling him yet! You'd be wasting your money, as you'll have to call him back once you have your plans in place, and can tell him where the loads will be, and how much the load will be. So I'd try to get your basic design done, based on your "number", then do rough calculations for two scenarios: no floating floor, and floating floor. Then call your engineer, show him both concepts, and see what he says. If he OK's both, then you can work on refining the basic plans based on budget, knowing that you are OK on structure. But if he only OK's the non-floated one, then you automatically know which way to go! Of course, if he rejects both, then you have a problem...


- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Ok. I have the structural engineer coming Thursday morning to inspect and report on the structural slab. I'll post his report here when I've received it.

But what I've learned is that my friend cannot wait the 2-4 weeks required for concrete to cure, so I believe that only leaves me with the possibility of a sand-filled wood decks. Do you agree?

Stuart, you suggested a "faux-float" for the floor on OC 703, but I'm confused about how that would work. In my experience working with that stuff, it doesn't have a spring-like behavior--it crushes instead of deflecting, and never rises again. I'm trying to imagine: Maybe that's not the principle here, and it's real purpose is to convert transmitted sound to heat via friction in the fiberglass -- but how can it do that for low frequencies, when it's so short in depth (compared to 1/4 wavelength) and has so little mechanical "give?"

I've found neoprene joist isolator U-channels on the web (http://www.soundproofingcompany.com/soundproofing-products/soundproofing-accessories/joist-isolators/ and http://www.soundisolationstore.com/joist-isolators-and-stud-isolators.html) that claim to decouple the new secondary subflooring layers from the underlying joists -- but it's hard to get data on the specs: What the "onset" and "overload" points of the springs actually are, in lbs. I called one company and they couldn't even tell me, and seemed unfamiliar with the concept. Are these to be trusted or employed?

Then there's the issue of sand. Rod Gervais rails so heavily on any wooden deck that DOESN'T contain sand that I feel like I have no choice but to buy a beach. But: is the sand the spring? Or is it a friction-load for sound, and I use it in conjunction with another spring, like the U-channels or fiberglass or whatever? In that case, how do you make sure you have exactly enough sand, and that it doesn't start to either short-circuit or destabilize the deck??? And how do I optimize the floor height (2xWHAT joists)?

You asked two questions I still haven't answered. Apologies:
1) I have not yet rested my finger on the floor, and put my ear up to it, to do the subjective "testing" you recommended. I will do so as soon as the lease is signed (tomorrow I hope) and we have the keys.
2) I still don't know how much Transmission Loss I need. Since I'm still tinkering with changes that VASTLY redefine my weakest link, I'm waiting to see what's possible before I get that detailed. I'm worried the answer will be that we really need more than we can get, but have to live with our maximum, given the time constraints. So I'm going with the strategy of "as much as possible" until I know the floor and wall TL's.

Thanks Stuart.

Reed

HI ...

Just following along on your build/design thread ...

Might be of interest ... when I was checking for flanking noise for my build ... including
the isolation of my monitors from the concrete block stands ...

It was suggested by mod/designer 'Gullfo' to use a stethoscope ... which I just happened to have from a 'broken' blood pressure machine [sometimes it pays NOT to throw everything out].

Anyway ... I found the scope very helpful in also locating studs in the ceiling when I was hanging clouds.

Many handy uses .... ahhhh .... but ya might want to be somewhat discrete should someone actually SEE you 'listening' through a wall ! Ya might want to have a doctors' smock handy just in case

Very interesting! And I just so happen to have one.

I'll give it a shot!

Reed

He's going to be waiting a lot more than that anyway! Rome wasn't built in a day, and studios don't get built in 2 to 4 weeks. (At least, not unless you have a whole army of framers, drywallers, builders, electricians, painters, etc. marching through your room, 24/7, (and stacks of cash to pay them).

Besides, you only need to wait a couple of days for the concrete to set up hard enough that you can start working on the rest of the studio. Yes, concrete strength improves over time, and 30 days is a good point to assume that it is really tough, but concrete actually carries on curing for YEARS, and never really finishes. A few days ago I read about some tests that were done recently on the concrete or a dam that was built 30 years ago, and it was found that the concrete is still getting tougher and tougher as it continues to cure...

Anyway, the point is that you'd only need to wait a few days to be able to carry on, and those few days could be well spent on additional design and planning. If you pour a new driveway, how long do you need to wait before you can walk on it? And how long before you can park your car on it? You certainly don't need to wait 4 weeks.

Exactly: it doesn't float at all, and is not a true substitute for a fully floated floor. Rather, it just decouples and damps. It's the same principle as a drum riser: break the hard mechanical contact between the surfaces by putting something soft in between. So any vibration in the floor deck is both absorbed and damped by the insulation, and not transmitted into the slab.

And don't worry: the insulation won't crush under the load. Let's say you manage to put a huge amount of weight in your room, including the floor itself, people, equipment, instruments, cases of beer, etc. Lets get ridiculous, and say you somehow managed to cram 2 tons in there. Lets go even wilder, and make it even worse: call that metric tons, not imperial short tons: 2,000 kilograms, or about 4,400 pounds. You have a total of 540 square feet of floor area, so that's a load of just 3.7 kg per square foot, or a it more than 8 pounds per square foot. You can't crush fiberglass with such a light load! If you cut out a piece of fiberglass that measures exactly one square foot, would it crush if you put a couple of bottles of coke on it? So there really isn't a lot of load on the fiberglass. And I totally doubt that you'll get anywhere near to loading your floor with 2 metric tons! Your loading on the fiberglass won't be more that a few pounds per square foot, maybe 5 or 6 PSF.

(Of course if you do a sand filled deck, that would be different, but we aren't talking about that here: Just a few layers of plywood, as per my original suggestion).

Exactly! If you are going to float a deck, then it doesn't make sense to do it without sand.

No, it's the mass. And it is self-damped mass, too, which is great. Sand doesn't resonate, ring, or vibrate. But the most important thing about it, is the mass: sand is heavy. It's a substitute for concrete, for folks who don't want to add water and cement to their sand...

You could, yes. Either of those would do the trick.

:) You use the equations...

If you "float" your deck on U-boats or other similar rubber thingies, then you have to ensure that the are loaded correctly, in accordance with the manufacturers specs. In other words, if the manufacturer says that you need to load each them to 100 PSI, and the measure one square inch of bearing surface, and your floor weighs one thousand pounds, then you need ten of them, spread around evenly, so that each one is loaded with one hundred pounds, which is one tenth of the total weight, (Yeah, I just picked those numbers out of my head, to make the math easy: real numbers will be a bit different! ) However, (and the manufacturers don't emphasize this vary much) your floor loading might NOT be even! For example, if you have a heavy wooden desk, with a large heavy console on it, and a couple of racks inside it filled with heavy outboard gear, plus some heavy LCD monitors, heavy speaker stands (sand filled), your chair, and you, all in one place on the floor, then you have a concentrated load in that area, but virtually no load in the rest of the room. Except at the back, where you have a heavy sofa with some heavy steel side tables, a fridge, and three heavy people.... Well, you get the picture: the load is NOT distributed evenly on the floor, so you have to take that into account when you place your U-boats, pucks, or whatever. You need more of them under the larger loads, fewer under the lighter loads, and it ain't easy to figure that out!

Also, the height of the floor gap isn't so important here, since the main spring isn't the air: the main spring is the rubber. Sure, the air spring also plays a part, and works in parallel to the rubber, so you do need to consider that too in your calculations, but the lions share of "spring" is on the rubber when you float your floor like this.

There's a few of those around, yes.

For a floated floor, you normally do it the other way! Since you are build a new frame on top of an existing surface, there are no "underlying joists". Your U-boats or pucks go on top of your subfloor, under your new framing, and you build your deck on to of that.

Yup!

If the manufacturer doesn't understand his own products, and can't tell you what the specs are, and can't show you detailed reports of tests done in INDEPENDENT acoustic laboratories, then I think you have your answer as to how much you can trust them!

Any reputable manufacturer will get their products tests in independent labs, and will be happy to publish the results if the product works well. If they don't test the product, then clearly they don't have much faith in it! And if the DO test it but don't publish the results, well that certainly leads you to doubt that the results were interesting!

So no: I wouldn't buy an acoustic product from a manufacturer who can't supply me with test results from an independent lab, period.

Like Rod often says: you have to live with what you've got. If you can't get a better place, and can't afford to do everything that you'd like in this place, then just do the best you possibly can, being aware of the limitations. It's a pretty logical philosophy, when you think about it!

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

Fascinating. Then I guess maybe the concrete is a viable option after all!

I'll see what the struct. eng. digs up on Thursday.

In the meantime, I just finished up banging out this Sketchup model. Rough openings aren't necessarily exactly mostly to scale. But most of the rest is, If I'm assuming I'll frame walls with 2x4, not 2x6. Also, I haven't dealt with incorporating any cant in the ceiling, or how we're gonna account for the duct chase cutting through the control room!

Maybe a concrete pour is just the amount of time I need...

Any suggestions for a primary textbook on HVAC design and assembly (Esp for studios?)? I've thoroughly digested Rod Gervais' treatment and now need a much more in-depth primer.

Thanks all!

Ok, tough day today.

The structural engineer arrived today and poked around the slab. He found that the structural floor is flat arch (terra cotta) and steel beams, 5' OC, with about 3" concrete above that -- it surrounds the top of the I of the steel beams and then forms the surface.

However, he also found substantial rust within the beams. This was apparent where it had blown out the terracota -- apparently, when steel rusts, it expands to 16 times it's normal volume, and that bursts the terra cotta and concrete. News to me. He could not readily assess how much rusting was going on on the beams, but he dismissed the idea out-of-hand of trying to make a secondary floor out of either a new concrete slab or a wood deck filled with sand. He said the structure could not bear it, let alone adding a substantial live load to it.

He also saw evidence of asbestos in the work -- the current floor tiles could be asbestos-treated, the caulking could be, and the piping could be. I'm starting to get a sense of the landlord as having skirted many of his own responsibilities in regards to this place. Have I mentionned that there are no sprinklers in the room???

His letter will indicate that the beams appear to be in a hazardous condition. But that said, it looks like we are going to pursue the space, with the idea that we will make a far less ideal build with far less weight. We may simply reinforce the subfloor with L brackets on our own and move forward with a build comprising a wood deck "faux floated" on OC 703, filled with soft fiberglass, and an inner wall and ceiling that "floats" on Mason Industries sole plate pucks, as we loosely discussed above.

Whew. New York is a tough city. I'll write more when I have a moment.

Reed

Wow. Not such good news at all. It sounds like that floor just isn't up to the task. Even worse, it sounds like it is questionable if it will even be able to handle just the walls that you will need for decent isolation.

Ooops. Fire code violation?

Did he also check the existing ceiling above the room, to see if it can handle the weight of your new ceiling? That would be one option for keeping some weight off the floor: If your inner-leaf ceiling is hung from above, then that weight is on the walls existing structural walls, not the floor, so it frees up some capacity for better walls.

I'll probably be off-line for the next few days, so you might not hear back from me until mid next week, but hopefully others will be able to answer your doubts in the meantime.

- Stuart -

_________________
I want this studio to amaze people. "That'll do" doesn't amaze people.

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!

Best,
Reed