Looking for some advice on isolation for new construction - AVS Forum
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post #1 of 15 Old 05-18-2009, 05:17 PM - Thread Starter
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So an architect is in process of finalizing my drawings for a 1st floor 3 Room addition, and I am at the point were I need to make some final decisions. So I turn to the experts for a bit of advice.

Theater room is 27x15x10 (half of the addition)
Floor is concrete slab (all three rooms will be on separate slab than rest of house). There is nothing above the addition other than attic space. This attic space will be separated from the rest of house attic space by concrete block - some minor punch through for electrical, etc. The two rooms adjacent to the theater will be a game room and an office (not true "living" space)

1) Back Wall - Concrete block - 1 inch air gap - standard 2x4 frame
2) Front Wall - Concrete block - 1 inch air gap - standard 2x4 frame
3) Side Wall - Concrete Block - 1 inch air gap - standard 2x4 frame
4) Side wall (separating theater from 2 other rooms) - 2x4 Staggered stud (2x6 sole plate)

I will do double drywall (5/8) with 2 tubes green glue on all walls.

Question) Is double drywall on ceiling necessary? I assume yes.

Walls and ceiling will be drywalled before soffits are constructed. A/C will most likely be housed in soffits, or come in through ceiling. I still need to determine best way to do this, since room will need a return (advice accepted )

Question) Even though staggered stud is decoupled, it is really still connected by sole plate, and also the door jamb. Anything else that needs to be done regarding the staggered stud?

Question) Is it necessary to put anything between framing and floor, or just anchor to bare concrete?


Although I know this question is subjective, is this "good enough?" Or are there additional things that will be NECESSARY to isolation?, i.e. What else is truly ESSENTIAL for isloation?

Basically I don't want to be that guy that everyone says "Can you believe that chump did DD/GG, Air Gap, Staggered Stud, etc, but he didn't bother to do XYZ, which truly negates what he DID do... and it wouldn't have been that difficult to do XYZ!

But then again I dont want increase my costs and effort 20% for something that will only increase isolation performance by 2%.

Thanks for all the help, I'm looking forward to your responses.
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post #2 of 15 Old 05-19-2009, 06:45 AM
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Wall framing next to concrete is right on. Install R13 fiberglass.

Wall separating the rooms I would really suggest double stud walls. Pic here: http://www.soundproofingcompany.com/...m_construction

You will need to decouple the ceiling as well. Clips are common, independent floating joists is better: http://www.soundproofingcompany.com/..._within_a_room

Send me your email address and I'll send you new Soffit Construction and Ventilation articles.

Doors, ventilation and lighting are the three biggest sources of flanking (leaking): http://www.soundproofingcompany.com/...icles/flanking

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post #3 of 15 Old 05-19-2009, 04:09 PM - Thread Starter
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Thanks for the great advice and articles. Can you clarify the "Floating Joist" implementation? From what I can tell, these new joists will basically lie on top of the decoupled side walls, which are merely bolted to the floor. Wouldn't this cause a major stability problem, i.e. what actually holds the "new" joists in place?
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post #4 of 15 Old 05-19-2009, 04:45 PM
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You're very welcome.

You have the scenario correct. You have 4 walls that are connected at the 4 corners. Moderate stability there at best.

Then we lay the floating joists on top. Screw up from the underside of the top plate into the joist to hold. Much better stability.

Once we start applying drywall, the structure becomes imovable. Just massive.

Many attach a DC-04 clip to stabilize the inner theater walls:http://www.soundproofingcompany.com/..._datasheet.pdf

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post #5 of 15 Old 05-19-2009, 07:21 PM - Thread Starter
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So basically the floating joists are merely for weight, and stability (they really don't tie into anything structural). I guess from there, you would DD/GG, screwing into joists at will, since they are decoupled!

I guess the downside is a lot of extra wood, and a pain for the insulation guy, since his normal distance between joists is now effectively cut in half.
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post #6 of 15 Old 05-19-2009, 07:28 PM
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Quote:
Originally Posted by WannaTheater View Post

I guess from there, you would DD/GG, screwing into joists at will, since they are decoupled!

Yes

Quote:
Originally Posted by WannaTheater View Post

I guess the downside is a lot of extra wood, and a pain for the insulation guy, since his normal distance between joists is now effectively cut in half.

Remotely cost comparable to clips, depending on what lumber you use. Insulation isn't a biggie.

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post #7 of 15 Old 05-22-2009, 08:18 AM - Thread Starter
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Just wanted to update: After room dimension analysis, I can't afford to shrink the theater width or the adjacent rooms anymore (I'm already pushing it). As a result, my room is as stands - 3 1" air gap walls, and one 2x6 staggered stud.

Does anyone know the best way to seal the gap under a solid door that is running over carpet? Or is a transition plate with weatherstripping really the only way to go?

Thanks!
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post #8 of 15 Old 05-22-2009, 08:28 AM
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You can't seal against carpet. Pretend you're holding back water.

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post #9 of 15 Old 05-22-2009, 09:10 AM
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I did the exact same thing with my basement - 4 walls with 2x4 walls separated from the concrete by about 1/2 - 1 inch. Soffitts attached to joists by clips. Clips for ceiling drywall. DD 5/8 inch and GG.

The differences are incredible. I can no longer hear people walking upstairs. I can't hear anything through the ductwork. I can't hear the water running through the plumbing.

I could only imagine after 30 days.

Soundproofing left to do: acoustic caulk at all openings, along floor. ...and of course I have to do something about the cheapo inside door leading downstairs.

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post #10 of 15 Old 05-22-2009, 09:19 AM
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Glad that's working for you, John

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post #11 of 15 Old 05-22-2009, 11:27 AM - Thread Starter
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Thats what I thought. I guess I'll try to find a fairly good looking transition to use...

Thanks Ted
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post #12 of 15 Old 05-23-2009, 08:09 PM - Thread Starter
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So given 3 walls decoupled from exterior block, and 1 staggered stud wall (16OC, I am guessing), are the DC-04's necessary?

Also, if decide to decouple the ceiling with hat channel/clips, how is the drywall actually attached to the track? Standard drywall screws?

I guess anything attached to the ceiling needs to be really well thought out (projector mount, soffit, star ceiling, etc) so it can hit the hat track... you now dont have the option to rig up joist-to-joist pieces of wood for mounting....

Again for me, nobody upstairs, and not really bordering any true "living spaces," so I'm trying to use the 80/20 rule

Thanks!
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post #13 of 15 Old 05-24-2009, 08:43 AM
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There is no 80/20 rule in sound isolation. You need to define the level of isolation you wish to achieve (which for playback rooms, is the noise floor IN the room, not the increase in noise floor in adjacent spaces). You then either achieve that goal or you do not. For listening spaces, the goal is at least NR20. If you don't care to go to that effort, then, when dealing with your architect, you need to establish what you want to achieve (with the full knowledge of what you are giving up) and then communicate that requirement to all the contractors working on the job (particularily, the HVAC contractor).

Quote:


After room dimension analysis,...

Explain this? Did you run some spreadsheet analysis for room modal response? If so, so what? First, larger is always better. Second, you're going to have modal response anyway and the way modal response is addressed in a "non theorically nice room" is exactly the same process for a "theorically nice room".

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post #14 of 15 Old 05-24-2009, 09:29 AM - Thread Starter
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Thanks Dennis. My room dimension analysis was a little bit less involved... The two adjacent rooms are already under 11' wide; I don't want to make them any smaller.

While I've already decided on airgaps and stagered stud for shared wall, and DD/GG for walls and ceiling, my decision now is on RISC/channel or no RISC/channel for for the ceiling. I know the ideal answer is "Do It," but I am wondering if I am just plain foolish if I do not.

As an aside, to me it seems like many of the folks on this forum have basement theaters in multilevel homes, where I would think isolation is much more an issue. Is this accurate?
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post #15 of 15 Old 05-24-2009, 10:00 AM
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1. Foolish if you do not; and,
2. No, isolation needs and requirements are the same for both types of construction.

Often single floor adventures, such as yours, are a bigger sound isolation struggle due to more walls being exterior/attic spaces...concrete block or no.

The big mistakes are forgetting you are preventing outside noise from entering the room not preventing room noise from leaving the room; forgetting that one of the biggest culprits of outside noise in, is poorly conceived and installed HVAC (including proper determination of cooling requirements for this type of space).

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