New "studio"/multi use space: tradeoffs etc.

Ahem, hello, first post. :-) First, let me say: wow, I've known some forums with extreme examples of people being amazingly generous with their time and knowledge, but this one should win some kind of award. So here's the basic idea: Building a new structure in the backyard: This will serve a couple functions, but I intend to continue my storied anonymous bedroom-studio musical career in there, and as we build this thing I'd love to do what I can to improve the acoustics along the way. In the image, north is "up". The dimensions of the building, rooms, partitions, etc, aren't really negotiable, unfortunately, given a ton of building code restrictions that we are directly up against and various other considerations I won't bore you with. Additionally, the north room, the bathroom, and the kitchen (just south of the bathroom) are not directly at issue here, just the south room and its loft space. The image shows the basic layout, and it is overlayed with a "loft". The loft covers the central third of the building. The bathroom/kitchen (5'2" wide) go down the east side of the building on the "ground floor". The loft is divided equally down the middle with a N-S partition. The E side of the loft also has a wall on it's north flank, and the W loft space has a wall on its south flank. I.e. half of the loft joins the room to the north, and the other half (the east half) joins the space to the south. What is probably not clear from the drawing is that the N room continues unbroken under the loft space, but there is a ground-floor wall that divides the N room from the S room that continues from the SW corner of the kitchen to the W wall. So, the south room, which is where the magic will happen, and where I hope to concentrate the special construction, if possible: 14'6" E-W, and 8'4" N-S. It has a very high ceiling: a sloped shed roof that will peak internally at maybe 16'6", and slope about a foot or two lower by the time it gets to the other side (low side is on the E). So it's a strange shape: the lower room just described, but that space joins with the loft space which is ~7'1" E-S by 8' N-S by ~7'6" high (with the ceiling for both spaces sloping slightly). Notes: - we are barely going to be able to pull this off, cost- and time-wise, to begin with, so isolation options are somewhat limited. - re-sale value and habitability is a consideration, so we don't want to shrink the room excessively, do anything too dramatic, etc. - it will likely be post-and-beam framing, about which i am still largely ignorant but I expect that changes some things dramatically when it comes to the external walls and flanking noise, etc. - probably a 4" poured concrete slab on tamped gravel, with no perimeter footer, just pilings under the structural posts. Maybe a thermal insulation layer under the concrete. - you may notice the planned use of pocket doors in a few places. We'd like them, not totally attached if it's a big problem. - the loft is currently planned as a wood deck (i know, i know). More on that later. - green glue looks great, but not going to use it given the amount of plastic involved in all the little tubes Goals: - highest priority is isolating between the loft spaces, and from the S room to the N room in general (S room to kitchen is not a direct priority). Ideally, I could play piano in there and not bother/wake the person in the N loft space or N room. Again, this isn't a studio-level requirement, here, just the best we can get away with on a budget. - isolation of external noise would be nice, but not the first priority for me. The occasional dog-bark, etc, is fine with me, in terms of recording. Lawnmowers, cars, not so much, but this will be a big step up for me anyway so I'm not sweating it. But if I can slap another layer of 5/8ths on there and get real benefit, I'm interested. It's just a lot of big walls to do that with... Current naive plans and beliefs (i got Rod's book, read it; i'm still doing my homework otherwise, so feel free to say "do your homework" on any of this): - considering staggered stud wall for the loft partitions (the whole 3-wall "S" shape that divides up the loft space). Maybe 2 layers of drywall on either side, maybe with RC. This I suppose must also apply to the wall that goes from the SW corner of the kitchen to the W (but hopefully not the wall between the S room and kitchen, if it can be avoided.) - considering extra layer of drywall on the inside of the exterior walls of the S side room, maybe with RC - probably we will have wood siding on the outside - 6" thick external walls likely, 4" internal planned (besides staggered stud walls of course) - not even worrying about treatment now, but after the dust settles i plan to build a bunch of DIY traps, etc. - I'm doing the electrical, and planning to do some isolated grounds to a sub-panel (still mining the great amount of info about that here.) - going to float the concrete floor using computer-controlled custom-designed hydraulic dampeners. Just kidding. Questions: - the big one: will flanking noise from the loft floor and ceiling and through the external walls make building the staggered-stud walls pointless? The posts are 6x6's, and maybe we could build in some isolation in the external wall if it would help? - given that throwing an extra layer of 5/8ths GB on the inside of the exterior walls in the S room doesn't dramatically improve things (only ~3 or 4 dB, if I understand things), and given that there will be a number of conventional windows in that S room (we don't really have the time/$ to do otherwise), am I wasting my time with those walls as well? - recommended courses of action for that loft floor: build it burly and put dry sand in it or something? Pour a thin concrete floor on it? - does post & beam completely change the game? I guess it really depends on the framing, and I can't tell you what that looks like yet, so maybe that's not answerable. - does this weird-shaped room bode well for the modal issues, reflections, etc, or is it a crap-shoot? - build the wall from the SW corner of the kitchen to the W wall, just the portion under the loft, out of cinder blocks and fill it with concrete? I'm hoping to do a time-lapse of the building process. :-) Ok, that's it for now! Eagerly awaiting your thoughts. Much obliged, -Casey