Yet another request for help with wall design...

Posted: Sun Nov 26, 2006 2:39 pm

Hi,

I have two rooms sharing about 12' length of 8' high wall. We are on a 24 inch crawlspace (there is an 8" foundation stemwall between the rooms). One room is a 16x19 bedroom and the other a 16' square media/sound room. Assume the media/sound room hits 100+db and that there is a lot of low to mid-frequency sound. I want the bedroom as quiet as possible.

We are remodeling these rooms and the framing is exposed. The shared wall is standard 2x4 wood stud on 16" centers. For practicality's sake, we are restricted to about 5/8" maximum thickness for replacing the sheetrock or other interior finish on the bedroom side. We have a few inches to play with on the media room side.

Here is what I am thinking about doing:

A. 5/8" QuietRock on the bedroom side.
B. Add a second standard 2x4 wall on media room side to create a double wall. I have a little bit of room to separate this new wall a tiny bit from the existing wall, maybe 1/4 to 1/2" or so such that they are not in direct physical contact.
C. Two layers of 5/8" QuietRock on bedroom side of double wall
D. 1/4" (2lbs/sf) MLV between QuietRock layers

Concentrating on the wall and setting aside other transmission paths, I would like opinions regarding the following:

1. Would sound control be better with 1/4" MLV under 1/2" standard drywall instead of just 5/8" QuietRock on the bedroom side of wall? (I could keep the MLV on the media room side, too.)

2. Would filling the wall space with batting be better than air? If batting is better, would rockwool be better than standard fiberglass?

3. Would an additional MLV layer between the double walls help or hurt sound suppression?

4. Would adding resilient channel supports on the media room side be worth the effort?

5. Do you have any general comments or ideas to consider in constructing the wall?

6. Anybody have a rough estimate of STC value for the proposed wall?

Thanks!
Gary

Posted: Tue Dec 19, 2006 12:05 am

Gary - get yourself over to John Sayers' website/board, where you can find hints, tips and pointers to places where you can find your answers, tricks to help you achieve your goal and a whole bunch of experience and knowledge/understanding/creativity. Google John L Sayers Productions

(you wanna put a 100+ dB room next to where the wife is sleeping? brave...)

Posted: Tue Dec 19, 2006 8:40 am

Hey, get Rod's book. Very good and detailed about a lot of this stuff. For the best isolation, he concludes that 2 layers of dry wall, studs with insulation, air gap, studs with insulation and 2 layers of dry wall will have the most attenuation of sound leakage between two rooms.

Posted: Tue Dec 19, 2006 7:20 pm

sushi-mon wrote:

Hey, get Rod's book. Very good and detailed about a lot of this stuff. For the best isolation, he concludes that 2 layers of dry wall, studs with insulation, air gap, studs with insulation and 2 layers of dry wall will have the most attenuation of sound leakage between two rooms.

And for some added LF response performance, use Green Glue between EACH the two layers of drywall. The better performance too is gained with thicker (5/8") gypsum board.

If you do NOT have load bearing walls, increasing the stud distance from 16" OC to 24" OC will also increase your LF performance.

Sure, you can use the quietrock, MLV, etc and get what, a 3db performance increase over the above outline, but at what cost difference? 3-5 times the cost?!? Not sure it's worth it myself... that's your call. Besides, you really do need to think about that flanking noise level...

Why have the ultimate performing walls and it's all for naught if the flanking noise effectively eliminates what you've tried so very hard to fix otherwise?

Posted: Mon Jun 02, 2008 4:36 pm

... Exactly the question I was hoping to get some feedback on.

I am building, this summer, a room-within-a-room assembly along the lines that Rod recommends in his book:

2 layers of dry wall, studs with insulation, air gap, studs with insulation and 2 layers of dry wall...

Like the fellow who began this thread, I am wondering about cost effectiveness. I have no problem dishing out 1000. for Green Glue if it is indeed the best solution. But - like our curious correspondent - I have gotten a recommendation for QuietRock.

I am off to the GreenGlue site now, but somehow I doubt I am going to get the most impartial comparison there. Does anyone else (who's been down this road) want to weigh in?

I gather that untreated sheetrock - even 2 layers - still carries some of those dread low frequencies. The question: if buying a material manufactured for the purpose - i.e QuietRock - might be more cost-effective than treating ordinary sheetrock in an expensive and time-consuming way (i.e. Green Glue)

The last post indicates it's hands-down, a no-brainer, that are we comparing apples & oranges? The comparison I'm interested in is between 2 layers of 5/8" sheetrock treated with Green Glue, and QuietRock at 40. bucks a sheet.

Posted: Mon Jun 02, 2008 5:47 pm

Quote:

if buying a material manufactured for the purpose - i.e QuietRock - might be more cost-effective than treating ordinary sheetrock

No. The double drywall will have increased mass, which reduces the MAM frequency.

Andre

Posted: Mon Jun 02, 2008 8:47 pm

If you are going to do double drywall then absolutely use green glue between the layers.
In this photo you can see the second wall that I had built inside of the existing framework of the house. I did the same thing with the ceiling, so the room is actually floating within another room down in the basement so it never touches the main level of our house above. The other good thing is that the three walls surrounding the backside are all concrete.

This is a close up photo of the double drywall wall with the green glue oozing out - still drying - they say it takes about 30 days for it to set properly. It took 5 cases to do this room at a cost of about $825 just for the green glue. They say its worth every dime to get that STC rating up.

Posted: Tue Jun 03, 2008 6:32 am

quiet wrote:

...
The last post indicates it's hands-down, a no-brainer, that are we comparing apples & oranges? The comparison I'm interested in is between 2 layers of 5/8" sheetrock treated with Green Glue, and QuietRock at 40. bucks a sheet.

That really is apples and oranges - BUT - for me - it's a no brainer......... at 40 bucks a sheet for quiet rock I'll outdo it with drywall and green glue all day long.

FORGET MLV............. especially between sheets of anything -

what it does add is gained when it is behind the sheets - able to be loosely fitted - able to move freely. COmpress it between 2 sheets and you loose just about all of it's damping ability and only gain the mass - which is a hreck of a lot more (again) than you would pay for drywall.

I recently was called into a practice studio for a gent who plays drums for broadway orchestras....... he plays a solid 115 dB inside his little 8' wide studio.

So 8' wide - maybe 28' long and probably 12' ceilings. This was an existing room inside of his studio rental - which is about 16 x 28 - so it cut it in 1/2 lengthwise - 2 x 3 wall - with 3/8" drywall each side - and a single steel hollow core door with steel frame and no weatherstripping.

Granted this is NYC and his building has concrete decks - roof (which is above his head on the16th floor) exterior walls and interior party walls between units (which is actually block with a plaster finish.

Before doing anything - readings in the hallway directly outside the room were about 85 dB A (slow) So the existing wall (and entrance door from the hallway) was good for a weighted average of a 30 dB reduction

We removed the outside face of the existing 2 x 3 wall - added a new 2x4 wall (with an 8" cavity between walls - for a total air space of 14") - with 2 layers of 5/8" added to the existing and the outside face of the new walls .......... we also installed double super doors.

We used Green Glue between all layers of drywall - so 3 applications total.

We also caulked everything up nice

When it was all completed you could only hear a faint whisper outside the door into the hallway. You couldn't hear anything in the neighboring apartment.

When he completes the entrance door (fills in the open mail slot - and adds weatherstripping with a drop seal) you won't hear anything in the hallway either.

That shows the true value of green glue in my book.

Rod

With just a single wall line

Posted: Tue Jun 10, 2008 5:59 pm

This is consistent with the results a friend got - who never expected things to be as isolated as they were.

Thanks for the help.

quiet

Posted: Fri Jun 13, 2008 1:28 am

I'm planning a room-within-a-room studio in a garage, in which I will be, among other things, playing drums.

I intend to build a double-layer inner wall sitting on rubber with a small (2 inch) air space between it and the outer wall. However, the outer wall is just 1/2 inch plywood, and it's not really practical to put another layer on it, though I will caulk up all the cracks tight.

Since I can't make the outer wall two layers thick, I'm thinking I should make the inner wall denser. Jeff Cooper's book shows an inner wall construction with a layer of soundboard between two layers of sheetrock. It seems that Green Glue between the sheetrock layers is an alternative approach.

I haven't priced out what the two approaches (soundboard versus Green Glue) would cost, but the garage is your basic 20 x 20 (inner dimensions are actually 19 x 19) with walls that are 9 feet tall and a vaulted ceiling that goes up another 7 vertical feet (so, 16 feet floor to apex of ceiling). That's a lot of materials, so I'm trying to gauge materials cost versus performance.

Comments or thoughts?

Posted: Fri Jun 13, 2008 6:01 am

larrytheo wrote:

Comments or thoughts?

Really, I just have one...

Please read this sticky, and create a new thread.

Rod's getting adamant about not replying to posts that don't conform to his simple request.

Max

Posted: Fri Jun 13, 2008 6:05 am

larrytheo wrote:

Jeff Cooper's book shows an inner wall construction with a layer of soundboard between two layers of sheetrock. It seems that Green Glue between the sheetrock layers is an alternative approach.

With all due respect to Jeff, the sound board isn't really all that great.

It doesn't compare with green glue - period.

Instead of sound board you would be better suited with an additional layer of drywall - more mass - greater LF TL values.
That having been said - you cannot make a cost comparison between soundboard and green glue because there is no comparison in performance.

This is the same as saying - "I need to buy a car - so I'm doing a cost comparison between a chevy malibu and a mercedes benz because I heard that both the Chevy's and Mercedes are good.

Doesn't make sense - does it.........

Rod

Posted: Fri Jun 13, 2008 11:54 pm

First, sorry for the violation of protocol. There's a lot of stuff on this board and even obvious "Read this first" stickies can sometimes disappear in the mass of messages, especially when one is eager to dive in. Having looked at that sticky now, it's all good sense, of course. So, mea culpa.

I should have worded my message better to reflect that what I was trying to ascertain was not simply cost differential, but balancing cost differential against performance differential. Clearly, considering cost alone is only half the picture. I could save LOTS of money by putting up corrugated cardboard instead of sheetrock, but to what end? So, thanks for putting that into perspective.

OK, I'll do my stickies reading homework now. I know I said the dog ate my homework, but that was just a fib.

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