The almost finished house I bought has some parts around the house that need some blown insulation. I've also already made some holes in my theater running wires to the speakers. While I have the insulation guys there, I was thinking of blowing in insulation in the ceiling of my theater to help somewhat with sound isolation. My questions are:


Is it a good idea to make more holes and blow in insulation between every floor joist cavity of the ceiling above the theater? I'm considering also double drywall + GG. The room above the theater is a kitchen with a tile floor. My only hesitation is, will a patched sheetrock hole be a sound leak, negating the benefit gained by the blown insulation?

Most advice on how to patch dry-wall has just the looks and durability of the wall in mind, not sound isolation. Is there a recommended way to patch dry wall with sound isolation in mind? Any dry-wall repair tips beyond the standard practice? I want to do this right. Thanks!

The ceiling is coupled (drywall attached directly to joists, so insulation will have less of a payback than if it were in a decoupled system, but still worth doing.

Not really worth the effort if all you do is every other bay or such.

Holes can be repaired as per normal, then apply next layer of drywall. All per normal installation, screwed back to joists always.

Since this is the one and only time you'll have a crack at this, I would point out that removing the drywall would allow you to signifiantly treat that ceiling:

- You could load up the existing subfloor to reduce footfall vibration.

- You could use cheaper R19 fiberglass insulation

- You could decouple with simple clip + track system

- You could then apply the double drywall to the track rendering a decoupled system.

- You can then damp as well.

The two ceiling systems would be signnificantly different in performance. Highly recommended if you are looking for low frequency isolation.

Ted, I considered tearing out the dry-wall everywhere and decoupling all the walls, but I really don't want to lose interior floor space (I can squeeze four theater recliners in now, but not if I decouple the side walls). So I had put decoupling out of my mind.

But I could do decoupling only on the ceiling, as I have 9'8" ceilings, and I don't mind losing a few inches on just the ceiling. But will only decoupling the ceiling be worth the effort, when I haven't decoupled the side walls? (though I would still do double drywall + GG on the side walls).

Also, if I did decouple the ceiling, demo-ing the existing dry wall ceiling seems like a big chore and a waste of a layer of drywall. What about blowing in insulation in all the cavities, installing isolation clips to the existing drywall, and creating a new decoupled ceiling on top of the existing dry-wall ceiling? Would this get me pretty close?

Can you spare an inch on each side? You can modify the existing single stud wall to a staggered stud in as little as 1/2": http://www.soundproofingcompany.com/library/articles/staggered_stud_wall_construction/

Also note that if you have a framed wall an inch away from the foundation, that wall is already decoupled. No need to do anything else, other than insulate with a bit or R13 and double rock.

If the existing ceiling remains there can be no decoupling without introducing the ill-fated Triple Leaf: http://www.soundproofingcompany.com/library/articles/triple_leaf_effect/

Can you spare an inch on each side? You can modify the existing single stud wall to a staggered stud in as little as 1/2": http://www.soundproofingcompany.com/library/articles/staggered_stud_wall_construction/

Also note that if you have a framed wall an inch away from the foundation, that wall is already decoupled. No need to do anything else, other than insulate with a bit or R13 and double rock.

If the existing ceiling remains there can be no decoupling without introducing the ill-fated Triple Leaf: http://www.soundproofingcompany.com/library/articles/triple_leaf_effect/

Thanks for the info on the triple-leaf effect. It sounds like I should either just double-drywall the ceiling, or tear out the existing ceiling and decouple the entire ceiling.

Luckily, this basement theater has three sides surrounded by foundation and there is already a decoupled wall that is insulated near each foundation wall:

http://i672.photobucket.com/albums/vv82/3fingerbrown/Stongegate%20House/IMG_1581-1.jpg?t=1258740846

I'm betting that the floor joists rest on the foundation, not on the stud wall near the foundation. But I guess you still have to worry about sound flanking upstairs.

However the wall with the door is not insulated, and is load bearing. This is the wall that would give the most effect by insulating, decoupling and staggering the studs.

So I guess just have to decide if I want to tear out the existing layer of drywall on the ceiling and the "door wall" and decouple the dry wall. This would mean having to redo the trimwork on the door, as we are widening the wall.

Or I just blow in insulation and add a layer of drywall and GG. Are there any numbers available that would give me an idea of how much improvement I get with each option?

3 walls that are already decoupled are likely not in contact with the beam. Those would get another layer of drywall and damp.

Ceiling options are as you said. Add a lot more mass to what you have OR tear out and re-do. This is a very significant component, and other can chime in, but I would really encourage you to see if this could be done. Drywall is $6 a sheet now.

That load bearing wall would not be compromised. All you are doing is extending a nail base out 1/2" or so. This in no way compromises the load bearing capacity (that I'm aware of). The original studs remain as-is. The only difference is that one of the two drywall faces is removed.

Then install the single solid core door at a minimum. Much better to have two back-to-back such that when closed they create an air lock. Very effective.

That load bearing wall would not be compromised. All you are doing is extending a nail base out 1/2" or so. This in no way compromises the load bearing capacity (that I'm aware of). The original studs remain as-is. The only difference is that one of the two drywall faces is removed.

Ted, are you recommending staggering the studs plus isolation clips? If I made do with just isolation clips on the existing studs, would that be a big compromise? I'm trying to preserve the width of my room, to fit four seats comfortably in the back. One more inch might not make that much of a difference though.

Ted, are you recommending staggering the studs plus isolation clips?

No. The staggering completes the decoupling. You could install the clips + channel directly to the studs as well, but it's easier / cheaper to stagger the studs, plus this method limits the room width loss.

If I made do with just isolation clips on the existing studs, would that be a big compromise? I'm trying to preserve the width of my room, to fit four seats comfortably in the back. One more inch might not make that much of a difference though.

I would recommend converting the wall to staggered rather than buy clips.

Ted

Are you saying that you will get flanking if you only decoupel the ceiling? Or is there something more to his room layout that leads you to this?

You'll get flanking of some form regardless of what you do. The area behind the walls up to the subfloor above is a common one. You'd want to reinforce your walls to the same degree as the ceiling. You would ideally have decoupled walls as well as ceiling if sound isolation were an imnportant goal.

You can accomplish decoupling via a few different routes. Decouple with framing is best and generally least expensive.

- Decouple with the wall framing away from the foundation. That's a decoupled double wall now.

- Decouple with a staggered stud wall.

- Decouple with clips + Channel.

- Decouple with a floating ceiling (new ceiling joists inserted in between the old).

All of these will decouple, though some are more effective than others. You would only do one. Clips on a staggered wall will do little more than you started with, for example.

Ted, or others, I have a few questions for you:


If you have 1/2 inch think drywall up already, and you want to add green glue + another layer of drywall, should you add another 1/2 inch layer, or go with a thicker 5/8 inch layer? I remember reading the layers should be the same, but I'm not sure about this.


There is a plastic one inch flex conduit running to the projector location. I will seal around this conduit tight with acoustic sealant as it enters through the drywall barrier. Anything else to be done here?


There is speaker wire already run along the ceiling (see picture below) I ran this before I started thinking about sound isolation, I was just going to hide it with crown trimwork. If I add another layer of drywall to these side walls, I'm not sure what to do about these wires. My options are: (1) pull the wires out, patch the holes, and install the GG + dry wall, and then re-install the wires (big pain but probably best for sound isolation), or (2) leave wires in place, install dry wall only up to the wires, and hide everything with the crown. But I think if I don't run the drywall to the corner its a potential major leak point. Any thoughts?


http://i672.photobucket.com/albums/vv82/3fingerbrown/Graded%20T206%20HOF/Stonegate%20House/theaterLCRspeakersrvsd.jpg?t=1258995149

1. 5/8" would be better

2. Seal as you say and life will be good. There's insulation in the cavity behind.

3. Holes and patching isn't a problem. Can you run the cable through a hole in the new sheet?

3. Holes and patching isn't a problem. Can you run the cable through a hole in the new sheet?

Not exactly sure what your advice is here.

This is my plan: 1. remove the staples holding the wires against the wall, so it the wires hang loosely against the wall. 2. Cut knotches in the new drywall sheets to serve as an entry points for the speaker wire through the new and old sheet rock, and slide the new sheet rock sheet under the speaker wire. Then I patch up leaks with acoustic sealant and hide the wires under the crown molding. Thoughts?

the knotched dry-wall and speaker wire would look like this, before I patched/sealed the entry points for the speaker wire:

http://i672.photobucket.com/albums/vv82/3fingerbrown/Stongegate%20House/newpic.jpg?t=1258998440

This would allow me to get a normal tight corner with the dry-wall and saves me from having to re-run the speaker wire.

New question: Overkill to stuff a strip of insulation/etc. under the crown molding to prevent resonation or other possible negatives?

That's fine. I see what's happening here. Just apply a dob of sealant where the notch is.

Not thinking the crown is sealed sufficiently to warrant insulation. Good thought, though.

I would recommend converting the wall to staggered rather than buy clips.

Wow. I thought clips and channel were there preferred method. So for a staggered wall do you use 2x6 as the base and then stagger 2x4s? Do you do this for all 4 walls? Is it different for and walls that are also foundation walls? And then I assume 5/8 DD and GG for theater side and then just single layer 1/2 dry wall an the other side of the wall. Correct? I think this would be a lot easier for my contractor and cheaper for me without the clips and channel.

EDIT: just to be clear Ted. My scenario is for new construction. I am about to start finishing my basement. Right now it is a blank canvas.

If you have a blank canvass, then do two independent stud walls. Better than staggered, better than clips.

If you have a blank canvass, then do two independent stud walls. Better than staggered, better than clips.

Thanks for the quick reply. Wouldn't this make any door jambs rediculously thick? I think since I was originally planning to do single wall with clips and channel, and if a staggared wall is better than that, I will probably go with a staggared wall. Thanks so much for your input. Just to clarify, with the staggared wall you would use 2x6 for the base and regular 2x4s for the studs? And you would do this on all 4 walls including the foundation wall (I have one wall in the theater that will also be a foundation wall.) Thanks again!!

In front of the foundation walls, just come in an inch and build the new framed wall. Since it's spaced from the foundation, that wall assembly is decoupled. The foundation counts as one of the double walls...

For staggered, yes, top and bottom plates are 2x6, and 2x4s are installed. The 2x4s can be 16" or 24" on center, by the way.

Thick walls, yet. Much better at low frequency isolation. Also good to consider a double door such that when closed create an airlock.

Your proposed walls will be in the STC 60+ range, while the door will be STC 28. Mighty big surface area for such a low score...

Thanks Ted and 3 finger brown, I apoligize for hijacking your thread. I'm getting materials delivered tomorrow so I guess it's time to start my own thread.

Good Luck!