upper floor load limit

[princeplanet]

I started a thread a while back asking for the pros and cons of building a small studio on an upper floor in an office building. Well, it looks like I'm about to purchase an 80 sqm space on the top floor of a building. The space is L shaped. I can provide more details if someone asks, but my early question has to do with floor leading capacities of upper level floor slabs.

After some trawling, I finally was able to be peruse the architectural plans and see that the floor is 125mm condeck reinforced (with shear studs). Apparently it has the same live load strength that some of the lower floors have despite them being (older) 200mm construction.

I think we calculated the load bearing capacity as being 350kg /m2. Now, of course there are many variables to consider before asking if this is sufficient for building a typical MAM structure upon it, so without being too specific, I can supply at least some of the more important info.

Control Room will be around 40m2 and the live room around 25m2. Using the existing outer shell as one leaf, the inner leaf will be the usual double 16mm drywall against 90x45 studs with the ceiling being 3 layers of 16mm drywall and the floating floor composed of 3 layers of 15mm compressed cement sheet under 16mm particle board flooring all above joists upon rubber.

For the control room, A 60 channel Neotek console and 2 large heavy main monitors are the heaviest items along with 4 x waist high outboard racks filled with the usual outboard. A lounge suite and some loaded shelves... thats about it apart from up to 10 people from time to time. The live room will just contain 5 or 6 amplifiers and a drum kit , a bunch of mic stands etc.

So nothing out of the ordinary. Does any one know some typical weights of small studios such as this? I basically need to know if the floor is strong enough and I need to know very soon in order to not be outbid for the space. Unfortunately, the acoustic engineer needs about a week before he can find the time to get some answers....

Oh, the other related question pertains to strength vs TL at low frequency. Although the 125mm condeck reinforced slab is as strong as 200mm concrete, I'm guessing it's less efficient when it comes to isolation? I mean, it's lacking 75mm of concrete mass... I guess that's why the engineer suggests 45mm of compressed cement sheet.

I'd really appreciate any thoughts chaps, I'm in a bit of a bind, time wise....

Thanks for reading!

[Soundman2020]

When it comes to structural engineering and safety DO NOT rely on advice you get over the internet! Certainly not mine: I've designed a whole bunch of studios, but I'm not a structural engineer. Even though I do design structures, I still always insist that a qualified, certified structural engineer should check them over, and modify them if needed, to meet LOCAL safety regulations and building code. You should most definitely do the same. Only a structural engineer who is qualified and certified to practice in Melbourne, Australia, can tell you what is safe for YOUR build in YOUR building, and only after inspecting it in person.

I can provide more details if someone asks, but my early question has to do with floor leading capacities of upper level floor slabs.

Without knowing the dimensions of your space, it's impossible to even guess at what the load would be...

I think we calculated the load bearing capacity as being 350kg /m2.

That's not very much for a commercial or industrial building. You would not even be able to safely put a piano on that floor! An upright piano can easily weigh that much, and more. Then add the pianist...

Also, inner-leaf walls are liner loads, not area loads, so you'd need to know the capability of the floor in terms of concentrated linear loads. The entire weight of all the inner-leaf walls and ceilings, is spread across an areas just a few cm wide, under the walls. A good isolation wall might well weigh 50 kg/m2, so a 2.5m high wall will weigh 125kg per linear meter. A one meter length of wall will therefore spread that load over an area of just 0.1m2 (one meter long, 10cm wide), meaning that the pressure on the actual footprint under the wall, is 1250 kg/m2... That does not take into account the additional weight of the inner-leaf ceiling, which will be transferred through the walls, into the floor.

the floating floor composed of 3 layers of 15mm compressed cement sheet under 16mm particle board flooring all above joists upon rubber.

... and you did the math to confirm that this structure actually will float? What size will each of your rubber pads be, and how will they be placed to ensure even distribution of the floor load? What are the resilient characteristics of the pads? What deflection do you need to get on those pads, in order to ensure that the floor still floats under minimum loading, and what is the resonant frequency of the floor at that load? Is it at least an octave lower than the lowest frequency you need to isolate? What is that "lowest frequency"? How much isolation do you need, in decibels? Will it still float when loaded down with ten musicians, all of their instruments, all of their equipment, your equipment, your gear, a couple of crates of beer, and a stack of pizzas?

If you can't answer all of those questions, then there's a problem... Also, the weight of that "floating" floor alone is going to eat up about 1/3 of your entire load-bearing capacity... it could easily be 100 kg/m2, from the way you describe it. Maybe more...

I basically need to know if the floor is strong enough and I need to know very soon in order to not be outbid for the space. Unfortunately, the acoustic engineer needs about a week before he can find the time to get some answers....

At this stage, you don't need an acoustic engineer: you need a structural engineer. Tell him to assume that your "floating" floor comes in at about 120kg/m2 ( to be safe) that your walls will weigh 150 kg per linear meter (to be safe), that your ceiling is another 75kg/m2, plus the couple of tons extra load for your gear and people.

Although the 125mm condeck reinforced slab is as strong as 200mm concrete, I'm guessing it's less efficient when it comes to isolation?

125mm of concrete will get you about 45 dB of isolation for airborne noise, but obviously not much at all for impact noise. Maybe IIC 25 or so.

- Stuart -

[princeplanet]

Stuart, thank you! This is helping me more than you imagine. Much appreciated. I'll make sure the structural engineer is across all these points. I think he and the acoustic engineer are more used to dealing with machinery noise in buildings, so I'm hoping they know what I need them to know about airborne sound such as is made by your typical indie rock band.

[Soundman2020]

Stuart, thank you! This is helping me more than you imagine. Much appreciated. I'll make sure the structural engineer is across all these points. I think he and the acoustic engineer are more used to dealing with machinery noise in buildings, so I'm hoping they know what I need them to know about airborne sound such as is made by your typical indie rock band.

But don't forget impact noise: Your drums, bass cabs, and electric guitar cabs will certainly put impact noise and vibration directly into the floor (unless you isolate those too), and so will things like foot-stomping musicians keeping the beat, keyboard pedals, effects pedals, and several other things. They all go directly into the floor.

Also coming the other way: Most buildings have machinery that puts impact noise into the building structure itself, such as elevators, pumps, fans, contactors, etc. As well as people walking on other floors, doors opening/closing, dropped things... You want to keep that OUT of your studio.

Impact noise is a bitch... Once it is in the structure, there's no way to get it out again....


- Stuart -

[princeplanet]

OK, Had a structural engineer on the case, but something seems not quite right. He says:


"The floor has been designed for a total load of 7.0kPa (700kg/m2), the proposed loads and the self-weights are in the order of 13.5kPa (1350kg/m2), I.e. the proposal nearly overloads the existing design capacity of the floor by nearly 100%.

This is based on the provided information, no required factoring of load has been applied, uniform distribution of load, uniform (averaged) capacities on the existing structure and we have not independently verified the calculations/capacities.

In short, we cannot support the proposal. It is not even close."


By your calculations, Floating" floor comes in at about 120kg/m2 ( to be safe) , walls will weigh 150 kg per linear meter (to be safe), ceiling is another 75kg/m2, plus the couple of tons extra load for gear and people.

That’s 245kg/m2 before other equipment and people are considered.

What am I missing? Just need a second opinion, ....

[princeplanet]

Edit, below are the ACTUAL figures that the acoustic engineer would have liked, that the structural engineer has been updated with. see the attachment for the L shaped space, of which the long side will only go half way down. The area below does not require isolation. The corner section will be the control room, the smaller section to it's left will be the live area.


-quote-
" Floor:
1. 15mm thick CFC sheet weighs approximately 28 kg/m2
2. 3 layers for the floor weighs 84 kg/m2
3. Insulation in the cavity will weigh around 4 to 5kg/m2
4. The purlins on top of the mounts would be steel prob 7 kg/m
Wall:
1. The wall sheeting will be 2 layers of 15mm CFC sheet with 13mm plasterboard over which will be around 68kg/m2.
2. Insulation to walls nom 75mm thick 32 kg/m2.
3. Mounts at circa 450 centres will be probably around 2-3kg/mount

Ceiling:
1. The ceiling will be 3 layers of 16mm fire rated plb or around 37.5 kg/m2 with 75mm thick 32 kg/m3 insulation over.
2. Penetrations etc for mech will need to be acoustically treated

Entry doors recommend airlock into the room 45mm thick solid core doors with full perimeter seals both sides of door frame.

The entry wall would be an additional stud wall internally not constructed off the floor with 2 layers of 16mm thick plasterboard facing the reception area"


-end quote-

I would have thought that support structures underneath the floor (they would be on the plans that the structural engineer has) would influence things. Nevertheless, I suppose I'd entertain halving the mass for the control room and and lessening the mass in the live area by 25%.

Would that be closer?

[princeplanet]

Hmmm, I'm still thinking this through.... so, my question was to find out if this system seems too heavy for a 125 bondeck reinforced concrete slab, which has an overall strength of 700kg/m2, but a live load of only 350kg/m2. I take it that with nothing on it, the floor could take 700kg/m2, however the existing walls and ceiling probably are weighing down on this slab (surely not to the tune of 350kg/m2??). I guess he (SE) is saying that I'm left with 350kg/m2 which is meant to be the live load allowance for every day office requirements. If you have the equivalent of 32mm of plaster on the floor, ceiling and 4 walls, and you flat packed it all, then the weight is something like 480 kg/m2. Only 130kg more than the live load, but on top of that you have the equipment and humans...

I'm hoping that the existing walls and ceilings are no where near 350kg/m2, even though much of it is floor to ceiling windows (8.3mm lam) so that we get a break there. One worry, however, is that the walls on the floor beneath are 1.5 metres further out than on the 7th floor (i.e., the 7th floor is a "penthouse" and is smaller with a balcony surround). Does that mean the existing walls are weighing on the slab more so than if the lowers floor's structure were directly underneath?

This stuff is beyond me. AllI know that my last studio had a 200mm slab built in the '60's and on the first floor it took 4 x the weight I'm proposing for this new site, and that is why I can't believe that a newer 125 reinforced slab, which meant to be equivalent to a 200mm slab, can't take the proposed weight.

Is the structural engineer being to careful? Or could there be a mistake in his calculations? After all, he said the total weight on the 700 kg/m2 would be 1350 kg -almost double- but the new structure could be around 500, the old one perhaps only 200, and the live load, well, it's a 48 channel console , some large monitors, amps, power supplies, furniture and people. much less in the live room.

But I don't understand how these figures all work. Is it worse when the load is concentrated along a wall line?

[Soundman2020]

which has an overall strength of 700kg/m2, but a live load of only 350kg/m2. I take it that with nothing on it, the floor could take 700kg/m2,

Nope! What it means is that the current dead load is 350 mg/m2, so your variable live load is the remaining 350kg/m2. The "dead load" is the floor itself, and the underlying stricture that keeps it up. Concrete weighs around 2300 kg/m3, so a slab 125mm thick is already 287 kg/m2, plus whatever beams, columns, and other sundries are under it / attached to it.


- Stuart -

[princeplanet]

I appreciate the thoughts. For those of you who have lost sleep wondering about the outcome , buying an extra coupla days meant we could reconfigure the design so we were putting walls on supporting beams from underneath- which we worked out for floor 6 plans. The structural engineer has okayed a new idea.

Without going into details, the other plans had walls along unsupported parts of the floor. Also, I think now the floors are ok to be 120 kg/m2. There is new thing though, that may even warrant a new thread! :facepalm: But now that my orientation has changed (again, I'll spare you the details), I think I'll need to have my control room 4.5 M long by 6.6M wide, yes wide! With a ceiling of only 2.9M (I've always been used to over 3.4), Im wondering if anyone has ever had issues with a wide control room. I know the dimensions are Bolt-ratio approved, but am used to bass notes travelling further behind me before they bounce back. On the plus side, I prefer to face long walls in a room for aesthetic reasons (maybe even psychological). Anyone think I could get used to it?

[Soundman2020]

I appreciate the thoughts. For those of you who have lost sleep wondering about the outcome , buying an extra coupla days meant we could reconfigure the design so we were putting walls on supporting beams from underneath- which we worked out for floor 6 plans. The structural engineer has okayed a new idea.

Excellent! That's good news, for sure.

Also, I think now the floors are ok to be 120 kg/m2.

Fine, but floating a floor can still be problematic. It's too late for me tonight, and I'm too tired to go into that now. More info available here: http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

You must be certain that it is floated properly, which isn't easy to do.

There is new thing though, that may even warrant a new thread! :facepalm: But now that my orientation has changed (again, I'll spare you the details), I think I'll need to have my control room 4.5 M long by 6.6M wide, yes wide!

Not good. I'd strongly suggest rotating your orientation 90° either left or right. With only 4.5m "length", your head is going to be very close to the rear wall.... way too close. Reflections will be arriving well inside the Haas time, thus messing up your sense of directionality, frequency, and phase. In other words, screwed up stereo image and sound-stage, and screwed up perception of tones. One of the most basic goals for a control room is to have enough space behind you such that any reflections and also the diffuse field, arrive at your ears only AFTER the Haas time.

This is all about psycho-acoustics, not so much plain acoustics. Psycho-acoustics is how we perceive sound, not how the sound really is. Our ears and brains are mindbogglingly complex, and do amazing things to form our perception of the sound. But one key for all of that to work accurately and cleanly is that there can be no "copies" of the sound arriving at our ears with a delay of less than about 20 ms: the Haas time. If you hear the direct sound, then a reflection of that same sound (or a diffuse echo of it) also arrives at your ears within less than 20ms, then your brain does not have enough time to catch up and figure it all out. In simple terms, it confuses the echo as being part of the direct sound, and does not identify it as an echo at all. Instead, it assumes that the echo was actually a phase shift and frequency shift in the original sound. Long story short: it tells you that you heard a different sound, at a different frequency coming from a different direction.

OK, so the effect is subtle, but it is there.

That's why we take such great care to build control rooms that keep all early reflections away from the engineer's head, and only allow the diffuse field (or reverberant field, if you prefer) to get back to his ears after a delay of at least 20ms, and at a level of -20dB below the direct sound. That gives our brains enough clues to figure out true direction and frequency.

So: Sound moves at very roughly 1 foot per millisecond. We need at least 20ms delay, so at least 20 feet extra path length. In other words, the sound coming from your speakers must go past your ears, then go ANOTHER 20 feet after that before returning to your ears. 20 feet is 6 meters, but it's a "there and back" path, so the rear wall of your studio needs to be at least 20 feet, (3m) behind your head. Actually, it isn't the wall that needs to be there: it is the front face of the acoustic treatment on the rear wall that needs to be that far behind you. And thus, the math does not work out for you, For that room, the mix position would need to be about 1.7m from the front wall, leaving just 2.8 m to the rear wall. But you'll need treatment in the rear wall, somewhere between 20 and 50cm deep (depending on how good you want your room acoustics to be), so you will have a distance of only 2.3m between your head and the closest reflecting surface behind you, Round trip = 4.6m = 15 feet = only 15ms delay. Well inside the Haas window.

Rotate your orientation to get the 6.6m dimension as your length, not your width.

There's nothing wrong with having a studio that is wider than it is long! Provided that it is also long enough to avoid the above issue.

but am used to bass notes travelling further behind me before they bounce back.

Right, but it's not just the bass notes! It's the entire sound field that is an issue. With the rear wall too close, it screws up everything. That's one of the reasons why you can't mix in a small room! And also one of the reasons why specs such as ITU BS.1116-2 and EBU TECH-3276 call for a minimum floor area of 20m2 for a critical listening room, as well as defining the allowable ratios and orientations to make sure that this is not a problem.

I'm working on the design for a mastering studio right now, and it's driving me crazy, because the space is border-line too small: I've been using every trick in the book to keep the path lengths as long as I possibly can, and it's starting to work out, but its complex. And that room is a bit over 5m long. so I can tell you from immediate first hand experience that is fresh in my brain: there's no way on this planet that you'd be able to make it work with just 4.5 m length.

I prefer to face long walls in a room for aesthetic reasons (maybe even psychological).

... but not for psycho-acoustical ones!

Anyone think I could get used to it?

Nope. Because it's not something you can get used to! It's a physical limitation on the capacity of the ear and brain to process sound. You can't get used to it any more than you can get used to living in a room that is illuminated only by ultra-violet light; You can't get used to it, because your eye is incapable of processing it.

OK, so maybe I'm overplaying this aspect a bit: it is possible to build a room that can be used to mix, in a smaller space. The issue is how good you want the room to be: If you answer that "mediocre is fine" then no problem! If all you want is mediocre acoustics in your room, then by all means make it 4.5m long. But if your answer is "excellent" or "world class" or "fantastic" or even "really good", then flip it to get 6.5m length. And if you want my opinion on mediocre rooms, then please take a look at my signature, at the bottom of every post!

Did your acoustician already explain all of this to you?

- Stuart -

[princeplanet]

Well, I know all this- I should- I've been running pro studios for 25 years and have built 2 of them already (well, had them built for me anyway). I do notice, though, that many rooms, particularly in in New York when I was there, seemed to favour wide control rooms, even looking at pictures rooms in US I notice this as well. It's hard to tell of course how DEEP these spaces are, and I would have thought 6M to be minimum dimension for depth, but then again wide rooms have the advantage of not copping so much reflection from the side. Granted, this can be dealt with, perhaps easier than a close back wall can, but are there any modern diffusion tricks or ideas re monitor placement that can perhaps mitigate certain sonic issues arising from said "wide" room?

Without going into detail, there are compelling ergonomic, functional reasons that would make the wide room more comfortable for both myself and the client. If I could learn to compensate for the coloured low end, I'd certainly consider going against the grain of conventional wisdom on this.....?

[Soundman2020]

Without going into detail, there are compelling ergonomic, functional reasons that would make the wide room more comfortable for both myself and the client.

If you can't go into detail, showing what the issues are, and explaining why they are a problem, then there's not much I can do to help! I'm not saying that I can fix the problem if you do explain all the boring details: it might not be fixable, as you say. But I sure can tell you that I can't fix it if I don't even know what it is!


- Stuart -

[princeplanet]

OK - so here's a copy of what I sent out to a couple of local acoustic engineers:


I’m considering a small studio build , and require a feasibility report (just a yay or nay based on the details below) leading into some detailed plans to hand over to an experienced builder.

Anyway, here’s a rough layout of the new proposed usage. Its on the 7th and top floor, with a wide balcony surround. Note that the entire north and west walls (and small part of east wall) are floor to ceiling glass windows (8.3mm lam). Also remember, these dimensions are raw, and that we will probably lose 200mm space (new surfaces and cavities) from all surfaces. (Current height to hard ceiling above ceiling tiles is 3.2m if we move out HVAC and services from above ceiling tiles).


(SEE ATTACHMENT FOR ROUGH DIAGRAM)

The concrete floor slab is 125mm reinforced with condeck.

Total load is 700kg/m2. The live load for the CR and LR is 350kg/m2. I’m assuming the point load for the walls is ok (had a structural engineer have a good look at the plans and all the walls for the 2 rooms have structural beam support below). I assume we just have the floating floor weight and equipment/ furniture /people to consider… (btw, we’re thinking of hanging as much compressed cement sheet from the existing roof as possible, for the outer ceiling leaf- less stress on the inner leaf...).


A problem with this design however is : which way to face the control room? North? Or into the LR?

Consider that musicians have to move from control room to live room a lot as well as into the lounge area and rest rooms (stairs down to 6th floor along the 709 wall ("Common property" is the stairs and corridor we all share). Now if CR faces into LR, then egress through a glass sliding door is possible, but I'fd like to avoid people from the CR needing to walk out into the corridor every time they need to go to the lounge/kitchen. With no room for a sound lock, this means a blast of sound getting into the common area, not to mention the extra hassle for the musicians to have to go into and out of the the corridor each time. One way to avoid this is to have a sliding door at the back of the CR that goes straight into the lounge, but as the room in narrow in this orientation, that messes up the back seating arrangement.

But now consider the CR to be north facing - i.e. wide orientation - then the sliding door in the same parts of the walls become side entry. Much easier!

But at the cost of a short front to back dimension. Is there a compromised solution that combines rear wall diffusion/bass trapping, monitor placement and room equalisation? If not a "world class" solution, at least a workable solution where I can still mix and master indie rock recordings at competitive levels?


Importantly, I do not expect total LF isolation in both rooms. I’d be happy to record overdubs, mix and master during the day at reasonable levels without disturbing neighbours. If I must, I could always record drums after hours (when office workers go home), but it would be cool to have a heavy duty drum booth as well as 2 or 3 small amp booths for when I simply had to record during office hours.


So, all up, I guess my main concerns are:


Will the slab hold a serious floating floor? Which design will ensure that it actually floats properly?

Is there a way to add steel bracing type reinforcement above the exiting slab (extending across to side support beams)?

Regardless of how the floor is reinforced and / or constructed, can we use no more than 200mm of space including a wooden finish?

Will new floor isolate down to 40hz and not annoy neighbours below and beside?

After losing space to isolation treatment, will dimensions be ok? Particularly height, can I get no lower than 2.9m in height? Is that high enough for a control room?

To create less weight on the slab, can the outer ceiling leaf carry much of the weight so the inner ceiling leaf need not be so heavy?

Can inner ceiling -including cavity- take up no more than 200mm space?

As drums are my biggest iso problem, could I build yet another raised enclosure (room with in a room within a room?) in the north east corner of the LR? Will the extra weight be a problem if it’s only 6 m2 ?

Can I have some internal windows on the north facing walls of both CR and LR? How big, how many, how far away from outer windows, what type, and should they be openable for cleaning?

Can i get HVAC out of the ceiling and into a wall panel? In both rooms? Where?

Can I get away with a wide control room as opposed the a long one?

What sort of internal treatment should I allow for (LF absorbers etc)?

Power and lighting ok if in separate conduits (minimize wall perforations)?

Woud I need to “star” earth? Would I need a power conditioner?

Is there a way, without compromising effectiveness too much, of building these rooms with a MODULAR DESIGN where wall (and perhaps floor and ceiling) panels can be neatly demounted and re-used elsewhere years down the track?



Happy to give more details…

[Soundman2020]

Challenge accepted!

And you can keep your CR facing the LR, oriented in the normal manner.... It is possible.... without needing any doors at all to the common area, from either the LR or the CR...

Will the slab hold a serious floating floor? Which design will ensure that it actually floats properly?

With only 350 kg/m3 live load capacity to play with, that is "iffy". I would consider doing a "damped deck" style floor instead. It is not a true floated floor, but it can provide quite a bit of isolation, especially for impact noise.

I do foresee a potential issue with your console, though. A 60 channel Neotek is a monster. It probably weighs 600 kg, at least. Spreading that over a small area is going to be an issue. Is the console a "deal-breaker"? Do you absolutely have to have that thing? It's going to be an interesting exercise to spread that weight over a large enough area to not overload the floor. It might be doable, but it's going to take some interesting design....

Is there a way to add steel bracing type reinforcement above the exiting slab (extending across to side support beams)?

It may be possible, but only your structural engineer can say for sure. I would guess that RSJ's would be the solution, but they would take up a lot of room height. Probably not the best solution. I would look into the possibility of reinforcing the existing slab by adding more thickness to it, with suitable internal structural bracing (rebar, steel mesh). If you make it thick enough, and do it well enough, then it will be able to carry more load (including its own increased dead load).

Regardless of how the floor is reinforced and / or constructed, can we use no more than 200mm of space including a wooden finish?

Yes. But a qualified "yes". It can be done assuming that one of the following conditions is true: 1) You do not need excessively huge isolation, or 2) If you do need excessively huge isolation, then you have a substantial budget that will allow you to get it with low-profile walls. You need the higher budget due to the need for more exotic (and more expensive) building materials. So assuming that either 1) or 2) is true, then yes you can have isolation walls in 20cm or less.

Will new floor isolate down to 40hz and not annoy neighbours below and beside?

Potentially, yes, but you will need to define "not annoy" in terms of decibels of isolation. You should do some extensive testing, with the cooperation of said neighbours, to find out what THEY consider to be "not annoying", measure how much isolation actually needs, and set that as your goal. Then define your construction budget based on that. With such a complex situation you cannot start out by defining your budget, then try to make it get the isolation you need: you must approach this form the other angle: Define what you need to do, then figure out the budget that will be needed to get there.

After losing space to isolation treatment, will dimensions be ok? Particularly height, can I get no lower than 2.9m in height? Is that high enough for a control room?

That's three questions in one! Let me split them out for you:

1) After losing space to isolation treatment, will dimensions be ok?

Assuming you mean "OK" as in "potentially world class acoustics in the control room", then yes, that is absolutely and certain feasible! The CR is not an issue. But assuming you mean "Abbey Road class acoustics in the Live Room", then no, that is not possible, because the main studio at Abbey Road is many times the height, width, length and volume of your LR. However, if you mean "OK" as in "A reasonably decent place to track, perform and rehearse for typical bands under the majority of circumstances", then the answer is "yes". 34 m3 is not large for a live room, but it is large enough to get a typical band in. It's not large acoustically either (in terms of wavelengths), but it's large enough that it can have a nice "character" to it, especially so, considering the high ceiling.

2) Particularly height, can I get no lower than 2.9m in height? ... (Current height to hard ceiling above ceiling tiles is 3.2m...)

Assuming that you mean the acoustic ceiling, then yes, it is certainly possible. I use a technique that would allow you to have your acoustic ceiling at around 3.1 m, or maybe a bit lower, but certainly no lower than 3.0m. But that's the height of the actual acoustic ceiling: there will be structural support members below that. They could be made visible, if you wanted that look, o they could be hidden. The lowest part of the visible ceiling could still be at or above 2.8 m, in all probability. It might even get close to 2.9m, with careful design, and a high budget to allow for exotic materials.

Of course, all of the above is with reference to the existing floor: It does not yet consider the height you will lose if you decide to float your floor, in some fashion. I can't take that into account, since we don't yet know how much room that would take, as it depends on may factors that are not known yet. But if you go with the "damped deck" proposal, your floor should take up no more than about 10cm. A properly floated concrete slab would take up maybe 15cm. (On the other hand, a floor incorrectly floated on rubber pucks and framing with layers of plywood decking, as you typically see on YouTube, could lose you as much as 25cm, and be very ineffective, or likely even make matters worse).

3) Is that high enough for a control room?

Plenty. More than enough. The toughest specs for world-class "critical listening rooms" calls for a floor area of at least 20m2 for stereo rooms, 30 m2 for multi-channel, and the classic "standard" acoustic response is referenced to a hypothetical room that has 100m3 of volume. Your CR has a floor area of around 34m2, and acoustic ceiling height of 3.1m. That's 106 m3 room volume. You hit all the key points very nicely. Your room ratio is within the Bolt area, and is rather nice, actually, with good modal spread, and a nice smooth Bonello chart. I see no reason why you cannot have a room that is every bit as good as this one: http://www.johnlsayers.com/phpBB2/viewt ... =2&t=20471 (Provided that it is designed as well as that one was, and built with as much care as that one was).

To create less weight on the slab, can the outer ceiling leaf carry much of the weight so the inner ceiling leaf need not be so heavy?

Assuming that there is available live load capacity in the existing ceiling above you, then it is feasible that it could carry the entire ceiling weight for both of your rooms.

EDITED! On re-reading this, I realized that you were saying something else, and I didn't really answer that. So about an hour later, I edited this post to add the following information:

You were asking if it is feasible to have a two-leaf system where most of the mass is on only one leaf, with very little on the other. Yes it is possible, but it is not very effective. The best configuration (see the Wyle report paper from 1973) is when you have roughly equal mass on each leaf. That gives you the highest isolation for the lowest mass and air gap (and therefore, for the lowest cost). Also, assuming that your current outer-leaf ceiling is a concrete slab, then trying to increase the mass of that by adding a few layers of fiber-cement boards to it, is not going to have much effect. Assuming that the ceiling is similar to the floor, the surface density is around 350 kg/2. Fiber-cement board weighs around 1550 kg/m3, so a 10mm sheet has a surface density of roughly 15 kg/m2. In order t get an increase if 6 dB in the isolation of your single-leaf slab ceiling, you need to double the mass. So you would need a thickness of twenty four sheets of fiber-cement-board to do that! That would be 230mm thick... and would likely overload the ceiling capacity anyway.... and all of that to get you just 6 dB extra. Not practical, not effective, and not cheap.

My suggestion was not related to that. What I was suggesting is that you leave the outer-leaf ceiling slab exactly as it is, but hang the inner-leaf ceiling weight from it, using suitable acoustic isolation hangers tuned to the correct frequency, along with suitable sway braces on the tops of your walls. That way, the weight of the inner-leaf ceiling would NOT rest on your floor. It would be supported by the outer-leaf ceiling. So that load capacity of your floor would be spared, and available for other loads. The only weight on your floor in this case, would be the walls, and the floating floor, or the damped-deck floor if you decided to go that way, as well as your gear and musicians. With a 600+ kg console, 8 musicians at 80 kg each, and another couple of hundred kg in their gear and instruments, you are going to need to free up all the load capacity you can. Consider this "freebie" to be my most valuable contribution to saving your project from the trash bin....

Can inner ceiling -including cavity- take up no more than 200mm space?

Yes. See above.

As drums are my biggest iso problem, could I build yet another raised enclosure (room with in a room within a room?) in the north east corner of the LR?

That would be a three-leaf system! It has potentially WORSE isolation for low frequencies (read: kick, toms, snare....). Here's why:

2-leaf-vs-3-leaf-700pix-from-wyle.jpg

I can go into more technical details on that if you wish, to explain why that happens, but there's the proof in real-world, understandable graphs. 3-leaf is great if you only need to isolate high frequencies, but not-so-great at all for lows.

Will the extra weight be a problem if it’s only 6 m2 ?

Probably, plus you would lose even more ceiling height... inside a drum booth! Drums need height to sound good. Not a smart idea to put them in a room with a low ceiling.

Can I have some internal windows on the north facing walls of both CR and LR?

Yes, you sure can!

How big, how many, how far away from outer windows, what type,

How big do you want them, and how much money do you have! They go together. The windows can be as big as your budget allows, and as big as the floor will support. There are also some acoustic restrictions on where the windows can be in each room, of course, but money is probably the bigger issue here, along with floor loading. Large sheets of thick laminated glass are heavy, and expensive.

and should they be openable for cleaning?

No, definitely not. And they won't need cleaning on the cavity side, if they (and the room) are built correctly. They need to be sealed in order to provide good isolation. I'm assuming that the building itself provides cleaning of the exterior windows, from the outside. The surfaces of the glass that face the wall cavity will not ever need cleaning. The only window surface that will need cleaning, is the surface that faces the room, which is easy to access.

Can i get HVAC out of the ceiling and into a wall panel?

You could, but why do you want it in a wall panel???? Studio HVAC registers (both supply and return) usually go in the ceiling, or at the tops of the walls. What is the reason for wanting to have the registers in the walls?

In both rooms?

Yes.

Where?

Wherever it is needed in order to provide the correct flow rate (volume) at the correct flow velocity (speed) for the occupancy situation of the room at any given time (number of people, amount of heat generated by gear, etc.), and the outside climate at any given time. In other words, the HVAC system must be designed such that it can can control the temperature and humidity, and provide enough air to keep everyone alive and feeling well, while removing enough CO2 and other nasty gasses, when the live room is full of crazily jamming musicians at the maximum planned/legal occupancy number, and the control room is also full of wildly partying people at the maximum planned/legal occupancy, on the hottest, most humid day of mid summer, without being overwhelmed, while also being able to do the same for one single calm musician playing lightly, with one single calm engineer in the CR, on a cool dry day, without freezing everyone. And it also has to be able to do that while not allowing any noise to get in or out. It's not s easy to do that! Tall order! You can't just place any old register wherever you feel like it, and hook it up to any old AHU or ERV, or whatever. HVAC is a huge part of studio design. I often spend as much time on designing the HVAC system, as I do on the entire rest of the studio!

Can I get away with a wide control room as opposed the a long one?

Perhaps, but with only 4.9m to play with, it certainly won't have world-class acoustics. You have a huge console, which will force the mix position to be way too far back in the room for good acoustics. Probably near the middle of the room, as far as I can figure.

And there's also no need to do that! As I mentioned above, there are options available to you that would allow you to have your CR facing the LR, without needing to have any doors at all into the common area (although you could if you wanted too). Whoever is telling you otherwise is not very creative, or not very experienced in studio design. The ONLY issue that might be problematic is the size of your monster console: whichever way you lay out the room, it's a problem. I'm surprised nobody has mentioned this yet, as that's one of the biggest issues I see for your CR. With your enormous console size, I would shoot or even thinner walls that what you mentioned: you'll need the space to just to fit the console into the room, resonantly comfortably, with reasonable access around it, in a reasonable location, and with reasonable acoustics. Large consoles in small rooms are an acoustic nightmare....

However, I would suggest flipping your CR with your LR: I would have the LR abutting the green room ("lounge/reception/kitchenette"), and the CR at the East end, facing west (into the LR). There are many reasons I would suggest doing that, but I'd prefer to not to reveal all my secrets in public!

What sort of internal treatment should I allow for (LF absorbers etc)?

For which room? The CR would need carefully designed treatment to achieve ITU and EBU acoustic response specs, such as the room in the link I gave you above. It could be done, or at least it could get very close to that. Once again, asking for specific treatment gets into the realm of proprietary custom acoustic design, and "I'd prefer to not to reveal all my secrets in public!" Suffice it to say, I'd treat that room in the normal way that I treat all high-quality rooms...

Power and lighting ok if in separate conduits (minimize wall perforations)?

Yes, but power and lighting can actually run in the same conduit, as long as that is permitted by building code. There's no reason why it shouldn't be allowed. But you do need separate conduit for your audio signal cables, and perhaps also for other wiring that you might need, such as alarm, CCTV, internet, telephones, intercom, etc. And yes, you will need to take care with wall penetrations, to retain the level of isolation that you need.

Woud I need to “star” earth?

I always suggest that star grounding should be used in a studio. It's one extra level of protection against ground-loops and other unwanted electrical noise.

Would I need a power conditioner?

Perhaps, but probably not, assuming that the power feed assigned to your area is stable and clean. You would only need power conditioning if there are known existing issues with the power feed, such as voltage swings, frequent brownouts, or electrical noise induced from building equipment, such as elevators, pumps, fans, etc. Hire an electrician to hook up a real-time line analyzer/recorder to your power feed for a few days, and monitor the conditions. If his report says there are issues, and they are serious, then consider getting a power conditioner, or SPS, or even a true UPS. Of course, if blackouts are frequent, then you will probably need a good UPS anyway. And if you need to run your studio at times when the building power or building HVAC is cut off (eg, nights, weekends, holidays, etc.) then you might also need a generator. That's big money! Hopefully not needed.

Is there a way, without compromising effectiveness too much, of building these rooms with a MODULAR DESIGN where wall (and perhaps floor and ceiling) panels can be neatly demounted and re-used elsewhere years down the track?

We keep on getting requests for modular rooms hereon the forum! It seems to be the latest fashion... Short answer: Yes, it can be done. Medium answer: ... provided that you have some extra money to throw away. Long answer: It is possible to design and build the studio as a series of sections, segments, or modules that can be bolted together, without compromising isolation or acoustics. However, that increases the complexity of the build slightly (as you need to seal all of the joints between modules such that they are air-tight), and thus also increases the cost (bolts, nuts, and washers are not cheap, when you need hundreds of them, and to pay the guys to sit there for hours and hours, tighten all of them correctly, and sealing the gaps, plus the sealant... ).

Then there's the issue of re-assembly elsewhere: you could certainly re-assemble the exact same pieces in other location... provided that the "other location" is the same size (or larger), and the same shape, with doors and windows in perfectly identical matching positions! If not, then you'd have to modify the design in any case.

And there will always be some damage, when you try to take apart a building assembly. It wont' come apart perfectly, it won't be loaded onto the trucks perfectly, it won't transport perfectly and there will be issues when you try to reassemble it.

Happy to give more details…

Me too! But not on-line...

Suffice it to say that I'm a bit surprised that you have already been talking to studio designers, and they have not come up with all of the above. There's nothing excessively complex or terribly out of the ordinary here, apart from the load limit. All of the other stuff you brought up can be dealt with, in ways that are commonly used when designing studios.

I’m considering a small studio build , and require a feasibility report (just a yay or nay based on the details below)

My response: "Yay, with caveats".

PM me, for more info, if you are interested.



- Stuart -

[princeplanet]

Another incredibly generous and detailed response! And I will indeed PM you, but I need to clarify and update some important details...

First, unfortunately - and I hope this is not a deal breaker - some detail about my existing ceiling. I went in again today to take some measurements, and the news is not good. Remember, it's an office, so there are office ceiling tiles when you look up. These are 2.67 m from the floor carpet. Above the ceiling tiles are all the services, large steel boxes and wide ducts for HVAC, wires galore and some 90mm PVC pipes (not for water) probably for more wires. Obviously we're looking at moving all the services out of there (not sure where to, maybe a rear part of the ceiling, or in a deep wall panel?).

Once the ceiling is cleared of ceiling tiles and all services, then we find a drywall ceiling which is under the actual roof of the building as we are on the TOP FLOOR. The roof appears to be tin, and has a slight slope south to north for rain runoff. The drywall beneath, presumably fastened to battens, follows the same angle, and it indeed loses 12 cm height from south to north. Consequently, on the south side of both rooms, the carpet to drywall ceiling height is 3.16m, but on the north side only 3.04m. There may indeed be a few centimetres between the ceiling drywall and the tin roof, and one idea might be to remove the drywall and stuff some dense material as high as possible between the battens, right up against the tin roof maybe. I have a hundred metres of 50mm compressed strawboard which could do the job if cut neatly...

So the ceiling slopes. The question is, does the CR finished ceiling need to slope as well? Or should it be flat, meaning the cavity above will be thinner at one end? How much cavity will we need?

Now, what you suggest re hanging some ceiling weight of the existing roof was interesting, BUT, you gave the impression you were under the misunderstanding that the ceiling was a concrete slab! It's a tin roof, albeit with some steel support, and is probably no where near as strong as a slab. My idea was that seeing we need a 2 leaf ceiling, we might hang as much as possible off the roof for the outer leaf. But you respond that both leafs need to be equal in mass. So, as an example, if we are adding 15mm of FC to the drywall off the roof, and 30mm of FC for the inner leaf, and leave a 100m cavity, then we have lost 145mm from the ceiling before internal treatments. So 3.015m at the high end, and 2.895m at the other end (BEFORE raising the floor!). Not the most mass dense or wide cavity ceiling, but perhaps it doesn't need to be, after all, there's no one above, and the balcony is 3 m deep all around before sound gets down and around to the lower neighbours. As for leakage through the ceiling to other neighbours on my floor, it is mainly an issue with the office next to the LR, which will need an extra barrier wall for further isolation. Not sure what else can be done there. Luckily people aren't often in that office!
.
Now getting back to your idea (when you thought the roof was a slab), I think you meant that we could fatten the roof/ceiling leaf without the need for an inner ceiling leaf.(I could be wrong, but let's go with it for a bit...) That would be great, because we wouldn't need a cavity, so my ceiling could be even higher! But surely there is a limit to how many layers of FC the roof will hold?? Perhaps the plans can tell us.... By stacking a single ceiling leaf (including in between the battens), then at best we may win back 100mm or so from the ceiling, THEN, if we can find a way to lose only 150mm from the floor, then we win another 50mm back, and that gives us a finished space of approx 2.95 at one end and 2.8 at the other. And I call that absolute minimum height I'm prepared to work under!

So notwithstanding the ceiling challenge, we have the, perhaps more critical, floor challenge. I'm assuming the best way to maximise T/L for the floor in 150mm or less is 10 layers of 15mm FC ! No pads, no cavity, no float... Surely the resonant frequency of that floor would be pretty low, problem is the weight, of course. Would be interesting to know what the best compromise is. A poured slab on springs I think will be too expensive, but happy to consider 150mm options that will be effective. I get the feeling a damped deck approach will not do enough...

So, single slab floor and single slab ceiling, more mass instead of cavity because we are space poor. Obviously weight is an issue, but what about the way that the double decoupled walls need to stay decoupled at the floor and ceiling? A slab on top and bottom "short circuits" the inner and outer leafs of the walls. So I am assuming that if the floor is a solid built up slab, then the walls would "float" on top of the floor via rubber decoupling?? Similarly, would the "slab" ceiling, which is hung off the roof structure, be made to "float" above the inner wall leaf with something like neoprene serving to decouple?

Or could the walls also just be "slab" like as well, no cavity, just thick mass. A designer in Melbourne likes to insist that 2 x 50mm compressed strawboard stuck to each other beats a cavity wall for LF T/L. I wish that was true, then my walls only lose 100mm instead of the 200mm I allowed for. BTW, the dimensions in the diagram have NOT allowed for any inner walls, so I hope the workable room dimensions you referred to took this into account....

OK, onto other matters needing clearing up, the Neotek console is in fact 40 mono channels with 12 stereo channels, and weighs, I think only around 450 kgs. It's 3.2m wide and around 1.3 deep. So probably not as long or as heavy as you thought, but still too long for the narrow version of the CR as opposed to the wide, which I'm pretty set on. But I will PM you on your idea to have the CR at the end, sounds crazy to me!

Triple leaf effect, I get it, but if the roof is tin, and we build either an outer leaf of single slab leaf right against it, then there's essentially no triple effect, no?

As for internal treatment, particularly LF absorbers in the back wall, what is wrong with the idea of a wall of diaphragmatic absorbers built into the back wall? It's a two-for-one in that it's a wall as well as an absorber. Can't be wasting no space with add-on absorbers inside the finished walls...

HVAC- school me! Both my other studios had split systems, so I have no idea (not that I have any idea about the rest of this stuff, I'm just riffin'... ). How much ceiling space do I need, at minimum, to give up to HVAC per room? And where? the front? back? the side?

Lastly, the MODULAR idea. Yes very appealing for obvious reasons. Here I must say that, after having just torn down my last studio, the idea of dismantling modular wall units would be a very clean alternative to the very messy job of smashing walls to bits and carting them away in bin skips. It took 4 people a month, it was expensive, dusty and dangerous. Not to mention wasteful! Unscrewing wall modules would take less time, have no waste costs, be much cleaner and safer, and be re-useable!!. I really, really wish my last place was built that way. Problem is, and I should have mentioned this earlier, that there are only people lifts, not goods lifts in the building. Only 2.2m high! Not only that, but the lifts only go to the 6th floor, I gotta climb a flight of stairs to get to 7th heaven (hmmm, not a bad name for the new studio....). Sooo, I was gonna ask if it's unheard of to construct modular wall units of say, 1.5m2 each. Not only would they be easy to carry, but they would fit in my lift! A double staggered stack can constitute a wall except for where the doors and windows go. Just gotta seal them and cover with pretty panels. I could even have the modules made off site, so as not to disturb the office neighbours as much during construction. Thoughts??

I'll leave it there for now and look forward to any response. Then I'd be only to happy to PM about taking this to another level where we can talk $$$

Cheers!

pp