My first construction project-Your help and advice needed

[smf1316]

I’m ready to venture into my first construction project. I'm planning on converting an apartment located on the second floor of an old (70+ years) wooden frame building (once a house in a former life) into a couple of small, fully equipped rehearsal studios, which I’ll be renting out on an hourly basis. Since I'm planning on sinking in most of my slowly dwindling savings into this project I want to make sure that I do it right the first time.
The first floor (below the studio) is a retail space, and I need to make sure that the noise transmission from the bands rehearsing upstairs to the business below is as minimal as I can make it. The existing floor of the apartment is oak. The idea of a floating floor obviously seems to be the best, but I'm a bit leery of the potentially claustrophobic effect of reducing the existing ceiling height, which is about 93 1/2 inches, much further. On top of that I may be butting up against local codes for ceiling height in commercial use (I'm still waiting for an opinion from the building department).
I had come up with the idea of covering the floors with GAF tri-ply, then carpet padding, and then commercial carpeting. I would then build floated ‘iso platforms’ (framed construction, a couple of layers of MDF with tri-ply sandwiched in between, carpeting, roxul underneath, all floated on neoprene -- basically individual mini floating floor) for each amp, PA monitor, and the drum kit. Would this offer the degree of isolation I'm going to need while avoiding dropping the ceiling height? I’m looking for some feedback on this idea. Anybody tried anything like this? Or should I float a floor using 2 x 2's instead of 2 x 4's to reduce the drop in ceiling height somewhat. Your input would really be appreciated on this 'dilemma'.
As far as the walls go, I'll be pulling the existing interior layer of sheetrock off of both rooms, insulting the wood framed walls with 3 inch roxul and then constructing a second wall inside each room, framed with steel studs and insulated with 3 inch roxul, and a double layer of sheetrock. Two layers of 5/8" or one layer of 5/8' and one layer of 1/2" - recommendations?
As far as the ceiling goes, I'm looking at a double layer of sheetrock hung on RC on the existing wood studs. Can I use regular pink insulation above or do I need roxul there as well (there's roof above)?
The two rooms I'm converting are perpendicular to each other, and share part of one wall. If I use the wall construction I'm talking about it seem to me that for about six feet there will be a triple leaf wall (steel stud wall/wood frame wall insulated with roxul but no sheetrock on other side/steel stud wall). If I simply leave the wood frame open with no roxul, will that give me a double leaf wall?
Lastly, what gauge steel studs should I use. My building supply guy says that I need to use 20 gauge not 25, but it seems that from everything I've read here, the more flexible the stud, the better. I've never worked with steel studs before (maybe you can tell). I don't want to use something too light and court disaster.
This is my first post here, but I just wanted to let everyone know that this forum has been incredibly informative, and I've been extremely impressed by the intellectual generosity and helpful nature of the participants. Thanks in advance for any input you can offer me!!

[knightfly]

Sorry for the short answer, gotta get to work in about 10 minutes - first, don't put carpeting under your floated floor, it's just a magnet for mites, mold, etc - I'll get back to this in a day or so with a lot more. You will DEFINITELY need to float the floor if you want decent isolation to/from below.

25 gauge studs are fine for two layers of wallboard (use both 5/8) but not if you will be supporting any ceiling frames. For that, you need the 20 gauge which are NOT flexible enough to act as RC; a single frame wall of 20 gauge would need RC on at least one side.

Need more detail on your existing ceiling frame before I can recommend hanging anything extra - also, hopefully a rough sketch of the total ceiling/roof construction, with sizing, spacing details... Steve

[Jai]

First, if you do not want to use steele studs check back with your city and find out if your building will fall under the grandfather clause. Meaning, in all citys that I have built in, if the original construction is wood frame than you can build with original matirials. I have only come across one city that insisted on steele in a 70+ year old building.

Second, get a hold of the original drawings of the building you are wanting to use. Will the original floor joists hold an additional 2+ tons built on top of them? If you float a floor, build walls on top of that, then put a ceiling on top of that, You are well into a ton and maybe 2 tons of added weight. That would and always has been my biggest concern building on a second floor situation.

Third, Building individual platforms that are floated for amps, drums, etc. will indeed help your situation, but will not make it go away. Floating eliminates (or really makes is much less) sound from going striaght to your support beems (or concrete slab on single floor) and transfering through your entire buildings framing system. So if you float a platform, and the sound is still hitting a wall in front of the drums that is attached to the floor that is attatched to the Joists, you are still getting it throughout your structure through the joists that you just spent time and money floating.


If your original support system can handle it, you are going to have to float the floor, build your walls on the floated floor, and then hand the ceiling on the walls you just built. thus giving you a two leaf system (Room within a room).

Floating floor diagrams are all over this site. but what has worked for me time and time again is cheap and works. That is....

2"x4" on its side framing - frame out your entire area on 16" centers
Place your neoprene (Please calculate what you need in duro strength) rubber at 16" apart. (some say 2' but you are using 2x4 on the side so you need the extra support)
lay in some 703 or rockwool in all the joist spaces.
Layer of OSB board (7/16") - caulk the hell out of it going down and then the seems
Layer of 5/8" sheetrock - Once again caulk good!!!!!
Layer of 1/2" plywood - Caulk better than good.

If you need cable runs under your floor you only have 2" space to do it so you will need severale 1 1/2" pvc runs depending on what you will be running.

The diferent types material is for sound proofing with different densities.

Like I said, there are a lot of ideas and ways to do a floor. This is what has worked for me on a bunch of rooms built. Chat with all these people and find a design that you understand and can build. If it works it's right. if it doesn't it's wrong. That is kinda my concept of what is the best method!!

just my 2 cents

[Innovations]

A while back I was researching other ideas and I came upon a thought for a thin, lightweight floating floor technique. What you do is to field-fabricate a glued panel of two layers of 7/16 inch OSB board between a layer of 7/8 inch Hexcel honeycomb to create a 1 3/4 inch hollow structural panel that I think could easily span two feet, maybe four in the strong direction (OSB is stronger in one direction than the other). You could then lay these right on the cushion mounts. You could hold back the honeycomb about 3/4 of an inch from the edge and then have a 1 1/2 inch by 7/8 inch insert strip so you could nail or glue them into an effectively seamless sheet. Could you put a wall right on top of these panels? Maybe but what I would do is hold the honeycomb even further back from those edges and use a 3 1/2 inch wide wood filler strip so that the wall is resting on solid wood (with sufficient cushion mounts underneath)

[smf1316]

Thanks for the advice so far!
Steve, I'll get some measurements for you tomorrow. In order to prevent sacrificing too much height I'll probably have to use the existing ceiling joists instead of building a new ceiling supported on the interior walls. I haven't ripped out any of the sheetrock on the old ceiling yet, but the support structure is most likely 2x6's, 16' on center.

[smf1316]

Here are the two rooms as the currently exist. All dimensions are current inside dimensions.
Room 1 is pretty straightforward in layout.
The ceilings in room 2 angle with the roof. As you can see, there are short doors on the east and west sides into a crawl space. That will make it relatively easy for me to insulate and sheetrock these walls. It would be great to try to preserve the use of these attic crawl spaces for some storage, but unless I can figure out a cost effective double door system which doesn't leak sound, I'll probably just close them up. I'm also going to eliminate one of the doors (the west one) on room 2, since what was once two rooms will become now become one. Interestingly, the partition wall in room two is built on the 'flat' - more of a 4x2 than a 2x4 frame.
I'll add another post which shows the relative position of the rooms to each other.
B/T/W, the west wall in room 1 and the north wall in room 2 are exterior walls. Anything special that I can/should do to them to try and mininmize transmiision to the outside?

[smf1316]

Here's the relative postion of the two rooms. The top of the screen is north--room 2 is at the top (in purple). The two rooms share a common wall of about 4 feet.