Hi Tom. Please read the
forum rules for posting (click here). You seem to be missing a couple of things!
Just to clarify what you want to do: You have an upstairs bedroom, and you also have a drum room downstairs, correct? And currently neither of the two rooms are acoustically isolated? And you are asking about isolating the bedroom, NOT the drum room? Did I get all of that straight? Just trying to make sure I understand the problem.
Anyway the room dimension is 17'8" by 15'4".
That's only two dimensions: you forgot the height!
The exterior walls (2 of these, ...) are 8" concrete block (hollow core ... The floor is a solid 8" concrete slab
That's a good start, for those three sides of the room. The problem is with the other three sides (two walls and ceiling).
(cars are parked underneath because the house is up on columns).
So where's the drum room? Also down there some place? Is it directly below the bedroom, or further away?
I have installed 1x2 furring strips on the exterior concrete block walls that I will attach my drywall to.
Mistake. If you have attached the furring directly to the concrete, and plan to attach drywall directly to that, then your drywall would not be decoupled from the concrete, which is what you need. As long as the drywall is coupled, you won't get isolation. What you need to do, is to decouple it. You do that by building a separate frame that does not touch the existing concrete block walls. Normally you leave a 1" gap then put up a 2x4 frame, and attach your drywall to that, in the normal way. You also put suitable insulation in the wall cavity, not for thermal reasons but for acoustic reasons.
This is a tuned system (technically it's sometimes called a "fully decoupled 2-leaf MSM system"), so the air gap needs to be deep enough for your purposes (another reason why the 1x2 furring is a mistake the air gap is far too small like that), and the drywall needs to be heavy enough for your purposes. That's how the tuning is accomplished. If it is not tuned correctly, it won't isolate the way you want it to.
That part in front of the 3 concrete block walls is fairly straightforward. The issue is what to do with the other two walls: Assuming they are typical house walls (2x framing with drywall on both sides), you'll need to take the drywall off your room side of those, then continue your new framing around those sides of the room as well, making sure that the new framing does not touch the existing walls. Once again, you fill the air gap with suitable insulation, then put drywall on the framing.
That just leaves the ceiling. The process here depending on what is above that: Another room? Roof? Attic? What type of construction? You mentioned joists and furring, but what's most important is understanding what is going on above that. Assuming that there is something substantial up there that can act as your outer leaf, then the best option would be to take off the furring that you put up (not needed, and not useful), put RSIC clips up there, then put hat channel in the clips and hang your drywall from that. And of course, once again, suitable insulation goes in the air cavity.
There might be other options open to you for the two framed walls, such as RC or RSIC clips, but we'd need more info to see if that is viable.
That just leaves the doors, windows, and ventilation issues. Windows can be sealed in place, and heavier glass installed, and doors can be sealed with rubber strips around the perimeter, as well as replacing hollow-core with solid-core if applicable. But ventilation is a big issue, and often overlooked.
This is a bedroom, which implies that people will be sleeping in it for long periods. I'm also assuming that the very reason it needs to be isolated is that currently people cannot sleep well in it, so it will need enough ventilation to keep a person alive and healthy for at least 8 hours. Since isolating the room acoustically basically means sealing it hermetically twice over, there's a need for a ventilation system that allows air in and out without compromising the acoustic isolation. It's not that hard to do, but it needs to be planned as part of the overall design.
What should I put between my exterior Concrete Block walls and the sheetrock?
A large air gap, no mechanical connection at all, and suitable insulation. By "suitable" I mean stuff that will do the job of damping resonance inside the cavity. In most places, that means either 30 kg/m3 fiberglass insulation, or 50 kg/m3 mineral wool insulation.
What about inside my interior walls?
Ditto. They key is to have a large air gap, at lest 4" deep, and not mechanical connection between the new drywall and the existing structure. Any mechanical connection at all, even a single nail, greatly compromises the isolation.
Should I double stack two sheets of thin drywall seperated by GG or simply attach a standard thicker sheets of drywall around the room?
That depends on how much isolation you need, which you didn't mention in your first post. But you did mention drums, so I'm guessing that you need a lot. The more mass you put on your new inner leaf, the better it will be for isolation. If you do go with two layers of drywall, then Green Glue does indeed improve low frequency isolation even more.
What about my floor?
Once again, that depends on how much isolation you need. It also depends on whether or not the sounds you are trying to isolate are both structure-borne and airborne, or only airborne. If you have structure-borne sound, then your floor will basically act like a loudspeaker, and transmit it into the room. Drums often flank into the building structure if they are not isolated, and so do things like bass cabs, so chances are that you do have a structure-borne issue. If that's the case, then carpet isn't going to do much at all. In fact, for structure-brine sound, the very best option is to eliminate the problem at the source, not the destination: build a drum riser to isolate the drums from the floor. Problem solved!
Of course, all of the above assumes that you have your drums in one room, downstairs, and that you are trying to isolate an upstairs bedroom from those drums, since that's what I understood from your original post.
- Stuart -
