The sketchup shows a void behind the studios, which looks like a waset of space but Im going to use this for storage and access to rear of studios for servicing etc..
Don't forget that that "void" is actually the "spring" in your MSM system! It is the air-gap between your two leaves that tunes your wall to the right frequency. It is also critically important that it is sealed perfectly: So if you have a door into that "void", as soon as you open the door, you lose all of the isolation to all of the rooms at once!
So that door would need to be very massive, extremely well sealed, and kept locked at all times when the studios are in use. You would only be able to access it when none of the studios are in use.
The same applies to the electrical closet: If it is locate inside the air gap, then all of the conduit and wall penetrations will need to be sealed very carefully: You'll have to stuff the end of each and every piece of conduit with mineral wool or fiberglass, then seal the end liberally with caulk, and you'll also need to seal and "mass up" the wall penetrations to match the same surface density as the rest of the leaf.
So do be careful when planning to put things inside your wall cavity! It can be done, but takes a lot more care and planning than you might imagine. It often turns out to be "false economy" for the same reason: You need to pay so much attention to detail to get it right, that it would probably easier to put that storage space some other place, and move the electrical panel to a more logical location, or re-arrange the rooms to that it does not end up stuck in a complicated position.
However, do I need to build a wall along the back of the studios or is this void ok as is?
If you wanted to avoid those issues that I outlined above, then yes, you'd have to build a single-leaf wall along the back of the studios, floor to ceiling, just as if it were an outer-leaf.
Anything obvious sticking out here?
As Steve already said: You will doubtless need permits to do this, as well as several inspections along the way, for several different parts. First you'll need some type of overall permit, which will require detailed drawings, and might need to go through several reviews before getting approval. Likely the electrical system will require separate permits and inspections from the framing, structural, and HVAC systems And since this is a commercial facility, it likely needs to comply with additional regulations, such as fire codes, wheelchair access, emergency exits, etc. So you should also budget for the fees of the people that you'll need to hire to get you through all that red tape: At the very least, an architect who knows the ropes and can do the drawings, then walk them through the approval process, plus a qualified structural engineer to check that your design is safe and won't fall down on your head, plus a qualified electrician to do the electrical plans and sign off on the actual electrical installation, plus probably others two. I'm not sure how things work in the UK, but each inspection might also incur a fee, tax, duty or some other expense. So do check out all of those in advance to figure out how much extra you should budget for those: Each individual fee, permit, document, and signature probably isn't that expensive, but by the time you add them all up they can drill a big hole in your pocket...
Steve also makes a very good point about insurance: If you don't conform to all the laws and regulations, with all your permits and inspections duly signed off, and then something goes wrong, your insurance won't cover it. even something as stupid as somebody tripping on a step or slipping on the bathroom floor then suing you, will not be covered: you'll be liable for all of that. And if it is something catastrophic, such a a ceiling joist failing and collapsing, injuring several people and damaging their equipment... well, all I can say is that I hope you have a very well padded bank account!
Not getting the right permits and inspections is a major risk, so do make sure that you have all of those in order.
I think I spent longer on sketchup than making the actual desk
Then you did it right!
Andre has an excellent rule of thumb: building a studio is 80% design and planning, and about 20% actual building. If you break that rule, then you are almost guaranteed of making expensive mistakes, or ending up with major problems, either structurally, acoustically, or functionally. So if your contractor estimates that the actual build will take a month, then you better make darn sure that you spent about five months on planning, design, calculations, drawings, permits, more planning, more design, quoting, checking, etc.
I know I am not sticking to leaf rules (or am I?) with the full length corridor, so Im a bit concerned about that?
Maybe you could mark the actual studio section in a different color, to make it clear which sections of the building need to be isolated, and which don't? It's not clear from your diagram.... And also mark the purpose of each room!
STUD/15mm OSB/12.5mm Drywall/OSB/Drywall
Don't use thin stuff! 12.5mm anything is too thin, too flexible, and too little mass to be good for isolation. Yes, there is a slight advantage to be had by using materials of different thickness, but the advantage is ore than offset by the loss of mass and loss of rigidity (stiffness) from using thin materials. So only ever use drywall or OSB that is at least 16mm, or even thicker if you can find it.
Also, I wouldn't put OSB or plywood on top of drywall: the wood layer(s) go first, on the studs, followed by the drywall on the outside. Drywall is not strong, and is brittle: it cracks, crumbles and crushes easily, and you even snap it by hand in order to cut the sheets to the right size, so it can't take any stress, structurally. So it's not a good idea to have very large heavy things attached on top of it, such as thick layers of wood.
So if you do want to use that set of materials, then make it OSB - OSB - drywall - drywall. And do consider using at least one layer of Green Glue in there, between two of those layers...
Q. Now that the ceilings are proving to be a potential problem, in this layout would I be spanning the corridor with I stud across corridor and insulating as per all other walls.
Right!
Q. Ive lost the liks to the room mode calculators - can anyone help please?
http://amroc.andymel.eu/
http://www.bobgolds.com/Mode/RoomModes.htm
I have dropped the idea of a performance studio in favour of this layout. It maxes out on income bearing space usage.
That's probably a good move: Spanning those long distances with heavy loads would have required large beams, trusses, joists, etc. = expensive! And it likely would not have been rented out nearly as often as the practice rooms.
The rehearsal spaces will be smaller than originally planned though (16'x17', 16'x13') - 3m high - any opinions on whether on this kind of space for band rehearsals?
Fine for small bands, up to maybe 4 or 5 people, but cramped for anything more. How about if you join two rooms into one at some point, so you have at least one larger room that you can rent out (at a higher rate....). You also seem to have a large empty gap in between two of the rooms: how about extending one (or both) into that area, to make them a bit bigger, even if it means giving it (them) an "L" shape?
- Stuart -
As for order i'm not 100% sure but alternating them would appear to make sense as it means the resonant frequency will change with each layer of material. Hopefully Stuart can give you some more definite advice on that one, but if you search around the forum you'll find someone has got some info on it.
Be very wary the helpfull tradesmen who give you advice about sound isolation and acoustics if they have not built studios before. Some of the rules and ideas for isolation can be counter intuitive, and advice that is well intentioned yet uniformed has the potential to really cause you trouble. And it's always going to be expensive trouble with a studio build. If you've got a tradesman giving you advice who has built studios before and can take you and show you their work, then fantastic. If not then avoid like the plague.