Hi Love528, and welcome!
Some quick answers, pretty much repeating what others already said in some places:
Based on your original post:
1. It looks like you have a reasonable basic existing structure. Should be usable, with modifications, but not the way you are planning right now!
2. Your budget is definitely on the low side (but I think you already know that!). Any chance you can increase it? Double would be about right, as a starting point...
3.
"has an access hole to the attic that I plan I covering up". Might not be a good idea to cover that up, unless there is an alternative access somewhere outside the room. There's a reason for those access holes: many reasons why you might need to get into the roof space at some point down the road. Can you put a new access hatch in somewhere else? It would be sad to spend all that money on building your studio, then have to tear a hole in the ceiling when you have a leak up there, or wiring issue, or whatever...
4.
"I’m hoping I don’t need a floating floor as the garage is on its own cement slab". I doubt that you will need to float the floor, but you cannot do it even if you want to! You do not have the budget! Floating a floor properly costs big money. 6K would maybe cover the cost of the concrete, without considering anything else at all (demolition, earth moving, springs, structural calculations, permits, etc.). So forget that idea, and in all honesty, you most likely do not need to do it anyway.
5.
"with possible flanking paths (that I could cut if need be) to the main house through a side walk". That sounds like it should be easy to cut. Probably not necessary, but if you can make a cut across the sidewalk and fill the gap with flexible sealant, that might help a little.
6.
"and it also does connect to main street through the drive way". Also probably not necessary, but once again it should be easy to cut and seal. A straight cut across the end of the driveway, where it joins the slab, and seal the gap. But DO CHECK WITH AN ENGINEER FIRST! There might be structural issues involved in doing that. However, both of these cuts are probably not necessary. And since you could do them at any time, even after the studio is complete, then maybe it would be best to wait until the end, to see if you need more isolation or not. Not necessary to do this up front.
7.
"I’m battling myself about going all out and building a room
within a room." If you are expecting levels of 110 dB in the room (And that's a really LOW estimate! they will most likely be more like 115-120, from what you say), and you need to get that down to a "not bothering the neighbors and family" point, or at least to the "no cops knocking on the door" point, then you really don't have much choice: full two-leaf decoupled, isolated, MSM room-in-a-room is the only way to go, really.
8.
"I could go in there and death metal yell very loud and barely hear anything inside the garage and nothing at all outside". There is a huge, major, big-time difference between a "very loud death metal yell" and a full-on rock band beating their brains out! The band produces roughly 1,000 times more acoustic energy... So you need roughly 1,000 times better isolation...
9.
"2 tubes butyl per sheet (instead of green glue)". There is no substitute for GG. If you go that route, you are on your own with how it might work out. No published research, no idea at all if it would help or harm. Butyl products are nowhere near the same as GG, and will definitely NOT have the same effect. GG is not glue (despite the name) and never dries. It is specifically designed to do constrained layer damping in sheetrock or wood walls. Butyl compounds are not. If you can't afford GG then DO NOT try to substitute something else! Just go without it completely, and add an extra layer of 5/8" drywall instead. You will get roughly the same effect from the extra layer of drywall. Of course, it will use up extra space, add extra weight, etc. but the effect is almost the same as a layer of GG.
10.
"and I may get me similar results to what I got with the MDF vocal booth". Yep! Exactly! You most likely will get something similar to what you had with the MDF booth... which will be about 1,000 times too flimsy for what you actually need for an entire rock band.
To understand the difference: Yes, you may well be able to scream at 100 db (maybe even 120!), but your voice only covers a small fraction of the spectrum that a rock band covers. For example, the human voice puts out practically no energy at all below about 150 Hz, but that's were the rock band puts out a huge amount of energy: Kick, toms, bass, keyboards, even electric guitars put out a lot of energy down in that region. On the other end: Your voice doesn't put out much energy at all above about 4kHz either, but the rock band sure does: crash, ride, hat, snare, guitars, keyboards all pour out rivers of energy up there. Next, your voice is a single point source, acting out of a space of a couple of square inches (your mouth, wide open). The band is MANY sources: point, linear and even planar (to a certain extent), acting over many square feet of area (compare the size of your mouth to the size of the heads on the kick drum, or the area of the speaker in the bass cab!)... It simply is not comparable. Your band will be putting out roughly 1000 times more energy than your loudest scream, and will do it across the entire spectrum, including the parts that your voice does not even touch, which just happen to be the parts that are most difficult to isolate anyway: the low frequencies, below about 150 Hz. You cannot compare a scream to a rock band, even if they both happen to clock 120 dB. No comparison. Think of this: In a big rock concert, the sound level might be 120 dB: The loudest scream ever recorded is something like 125 dB. Do you honestly think that the guy that managed the loudest-ever scream could stand next to the speaker stack at a Grateful Dead or Pink Floyd concert, and drown out the entire concert with his scream? Uhhh... nope! Do you think he would even be HEARD more than a few feet away? Ummm.... nope! Even though he appears to be 5 dB LOUDER, there simply is no way that he can compete, simply because of the total amount of acoustic ENERGY going out. It's not just about relative sound levels: it is about spectrum, and it it about total surface area, and total acoustic energy output. That's just a long-winded way of saying that your "death metal scream" is not a valid measure. Final thought experiment: Do you think that you could pack the entire speaker stack from Pink Floyd into your booth (or as much as will fit!), play "The Wall" at 120 dB (or whatever the level of your scream was) and expect to hear nothing at all outside?
Case closed....
11.
"one possible factor that helped the isolation with the vocal booth is that the garage has carpet (the booth was sitting on) with a rubber pad under the carpet and I think the booth was kind of floating due to this" Not really "floating" in the technical sense, but probably fairly well decoupled... for
voice frequencies. However, once again that was a VOCAL booth, not an entire rock band. Orders of magnitude difference in levels. In any event, the carpet will have to go when you build the room: Pretty lousy, acoustically. Lose it, and just leave the bare concrete (or laminate floor).
12.
"what makes this project hard is my families bedroom is 10 feet from the garage and I know kick drum and bass guitar are going to be the problem if they are trying to sleep." Yup! You just defined the issue perfectly. Your voice puts out no energy at all in the region where the kick and bass are sizzling. Your booth won't even touch those low frequencies, even if it did a fantastic job of isolating your death metal scream. Its a case of comparing apples vs. oranges. Or maybe "grapes vs. watermelons" would be more accurate!
13.
"I plan on making a floating drum riser just like this Auralex one for the drums and I’m going to put the bass and guitar amps on Gramma pads to decouple them from the floor, hoping this helps a little to dissipate the bass energy, every little bit helps right???" Yup! Now THAT is a good thing, and will work. A drum riser and cab pads will certainly help to keep the bad stuff out of the floor slab, and you will need those ANYWAY, even if you to a "room-in-a-room". But don't bother buying commercial ones: You can't afford them on your budget, and you can make similar things yourself, easily and much cheaper.
14. HVAC: You MIGHT be able to use the cheap window unit, but NOT with the trash-bag idea:
Use the exchange chamber idea instead (see Rod's book). Do it right and it will work. But forget the trash bags!
15.
"I actually like this idea better than a mini split, cause these AC’s allow fresh air into the mix,". Yes, but you still need an additional duct to exhaust stale air. That can just be a simple fan and duct system, though.
16.
"Plywood for floor 5/8” 9 sheets 4x8 $250
Plywood for floor 2nd layer ½” 9 sheets 4x8 $200"
Forget that. You don't need any floor. The concrete slab is fine, nad is already there, so it will cost you ZERO to do the floor!
17.
"2 sheets of Laminated glass 3x2’ $200" Way low! The kind of glass you need is going to be WAY more than that (unless you are talking about postage-stamp sized windows! Maybe that should read 2" x 3", instead of 2' x 3' ???
) 200 bucks will NOT buy you 12 square feet of 1/2" or 3/4" laminate glass! Not even close.
18. Room layout: Looking at your first diagram, I would flip it completely around, 180°. Have the console facing the wall at the top of the diagram, and the couch under the windows. MUCH better, for many reasons.
19.
"still need one layer to nail some nice oak hardwood flooring to (I might possibly score)." Nope! Just lay ordinary laminate flooring. You do NOT need to nail it to anything! It just sits on top of the existing concrete slab (with an underlay, of course!) but is NOT attached in any way. The plywood flooring will not do anything for you at all: no acoustic benefit (probably make things worse, actually), no aesthetic benefit, and no structural benefit.
20. Doors and windows: You need to pay a lot more attention to those! Your diagram shows 2 doors and 2 windows; each will need to be doubled up. Each will become a back-to-back pair with an air gap between.
21. "
my bad I forgot about the genie clips for the roof and I am aware of that aspect as well as better ways." Not just the clips! You need to add hat channel too. And forget the drop ceiling: no useful benefit.
22.
"In my case I think I'm going to have to use genie clips cause I don't want to put up truss beams as they would eat up too much of my ceiling height." Not necessarily! You STILL need the air gap between outer leaf and inner leaf, regardless of how you support the new inner ceiling. You still need at least 4" of air gap, and preferably more. You will lose that height regardless. There are methods you can use to gain back that height, but it involves some extra work on your part: demo the existing ceiling, and put new drywall on TOP of the existing joists, instead of underneath, then interleave your new joists between the existing ones....
23. Mineral wool / fiberglass: You do not have any at all in your budget!
For proper "room-in-a-room" construction with proper two-leaf MSM walls and ceiling, you MUST install mineral wool or fiberglass insulation in the air gap. You need at least 2 inches in the gap, all the way around the entire room, on all five sides. 4 inches would be better if you hope to achieve the kind of isolation you are talking about. If you leave out the insulation, then you leave out the isolation too: forgetting to put wool in the wall will cost you around 10 dB of isolation, and maybe as much as 16 dB. That's a biggie!
24.
"Anyone know if buytl is a decent substitute for green glue?". Answer: No it is not.
25.
"a few of the studios my friends have built used butyl and it seemed to work great and was much cheaper than GG"Well, I know of people who put egg-crates on the wall and glued carpet to the ceiling too, and thought it worked great! Until they took it down and treated the room properly, then realized what dunces they had been before.... Not to insult your friends, but the butyl was a total waste of money at best. It may well have damaged the acoustics in ways that nobody will ever know. Unless you can find some published studies by reputable acoustic researches or independent labs, detailing exactly what butyl does and showing the graphs and equations that define its behavior, then forget it. You have absolutely no idea what it is doing.
Summary: You probably can achieve what you want, but you will need to go full decoupled MSM, room-in-a-room to get the kind of isolation you need. But your budget is definitely on the low side, not realistic in very important thins (glass and HVAC, for example) and you are not including some very important materials (rock wool / fiberglass, for example). You also have not yet considered what to do about the laundry/bathroom, and you don't show where the laundry door is. Could be major issues. You also have not said much about the roof: another potential major issue.
I'd suggest that you revise your budget, and do a full and accurate design in SketchUp of what you have right now, with all major structural parts in place, so we can figure out the best way to isolate it to the level you need, and at the lowest possible cost.
- Stuart -
Though I did take out the garage door, frame it
etc.......