Double width studs for isolation?


Before I drywall my new dedicated room I was wondering if it would be at all beneficial if I added an extra stud to each/some of my 24" on center studs to increase the amount of surface area the drywall was screwing into and thereby conceivably decreasing the "intensity" of energy transfer through them into the outside walls? My goal is to reduce noise transmission through the walls. I will be using 2 layers of 5/8" drywall with Green Glue between. It's not a lot of extra work and I already have some extra studs. Just a thought. Thanks. Grant
lissnr
I had heard that staggered stud construction was good for isolation. That's what I did.
http://www.diy-home-theater-design.com/staggered-stud-wall.html
1. Studs should be 16" on center.
2. Use 2X6 lumber (Good, but not essential).
3. Apply 1/2 inch sheet rock.
4. Apply a layer of styrofoam (or other lightweight plastic insulation panel). One inch thickness is fine.
5. Apply another layer of 1/2" sheet rock.

5/8 sheet rock is to avoid sags between ceiling rafters which are on 2 foot centers.
Be sure the studs rest on isolation materials at the header and base strip.

I'm looking at dedicated room but I have challenges with the main water line. The main water line along with the cut off valve are on the primary wall where I need to stud and sheet rock for AC and placement of components and speakers.

The water line sticks out from the concrete wall a good 7 inches so if I stud the wall I would have to move the cut off valve to different place for access.

How would you approach the problem?
Apply a layer of Styrofoam: Please be aware that the NYC fire dept has done studies with Styrofoam installation. Applying Styrofoam vertically increases it's potential to catch and spread fire much more quickly than when used horizontal.I could only guess that gasses from the Styrofoam are released at a faster rate in a vertical position. I would use a flame retardant installation inside any wall project. I am only concerned with every one's safety.
Schipo...I believe that if the styrofoam is sandwiched between sheetrock layers it's safe. Exposed to air inside a wall is a problem.
OK, I'm going to do something I've never done here publicly and state my credentials: MIT - B. Architecture + Acoustics, (e-mail me privately if you want to know the year ;-)

Acoustical treatment/construction solutions will depend on which of two categories the problem fits. (1) Transmission from one space to another (one of the spaces can be the outdoors) and (2) reflection/reverberation within a space. Sometimes both are issues, but they still require vastly different approaches/solutions.

Eliminating transmission (the issue Grant is dealing with) is accomplished through MASS+STIFFNESS and/or ISOLATION. I emphasize this, because stuffing a wall cavity full of fuzz (Fiberglas, or other ABSORBTIVE material) is futile, unless of course your termites have been complaining about the sound reverberating in their little ears!)

'Staggered studs' will physically separate the wall surface in one space from the wall surface in an adjoining space and is an excellent solution (for 2x4 or 2x6 studwalls) if the ceiling in ONE of the spaces is less than 9 or 10 feet. If both spaces have higher ceilings, then even with staggered studs, the air inside the studspace will still couple the two surfaces together enough to cause induced vibration in the 'receiving' space (whether not the studspace is stuffed with fuzz ;-)

Having isolated the two surfaces from one another, further attenuation (if necessary, which it often is with 2x4 studs, not so much with 2x6's because they're stiffer) can be achieved by adding mass. The most straightforward way to do it is to add another layer of drywall -- first on the 'transmission' side of the wall, and then, if necessary, on the receiving side.

In the days before drywall it was difficult (OK impossible) to add more mass to a (plastered) wall surface. Plaster has much less mass than drywall, and it doesn't like to be laid on too thick (like I'm doing now!) In those days, a (literally) curtain of sheet lead (yikes!) was often threaded between the staggered studs to eliminate the coupling problem. It's really unnecessary to do that today, but the technique (they don't use LEAD!) is still very effective (along with resiliant, or 'floating' floors) for vertical isolation (rooms above/below other rooms.)

While on the subject of 'resiliant', it IS possible (but not practical or cost effective in residential applications IMO) to 'float' a wall surface in front of another wall surface by hanging a second sheet of drywall (in front of the first) on resiliant (springy) metal clips designed absorb the energy of the sound wave against the wall surface. In a home, it's a real PITA because a 1/2"+ space must be maintained at all the edges of the 'floating' wall surface and filled with caulking or foam rubber, etc.

If you have an existing (partition) wall (between two spaces) and want a quick-and-easy solution to reduce the sound transmission through the wall, my recommendation would be to just add another layer of 5/8" drywall to both sides and see how it goes. TIP: using lots of x-tra drywall screws creates a 'stressed-skin' effect in the added drywall layer, which increases the stiffness of the wall.
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Nsgarch...I too went to MIT, but was more interested in women than calculus. Tech Hi Fi in the warehouse also, Graduated elsewhere; Pratt Institute of which, as an architect you are probably aware.

As to acoustic isolation, my expertese is that I actally did a room with the foam insulation sandwiched between sheet rock. I did it for thermal insulation, but was astonished by the acoustic isolation result.

Stagered studs have pros and cons. It minimizes direct transmission through the wall, but, with sheetrock on only one side of the studs the walls are not very stiff.
Nsgarch...I too went to MIT, but was more interested in women than calculus. Tech Hi Fi in the warehouse also, Graduated elsewhere; Pratt Institute of which, as an architect you are probably aware.
Yes, eldartford, Cambridge was an interesting place in the early 60's: Tim Leary, Lou Reed and Andy Warhol (no comment ;-) My 4th floor walk-up was neatly sandwiched between the AR and the KLH factories ;-)
As to acoustic isolation, my expertese is that I actally did a room with the foam insulation sandwiched between sheet rock. I did it for thermal insulation, but was astonished by the acoustic isolation result.
What you did, from a structural/mechanical POV (in addition to the thermal thing) was to construct a (kind of) laminated skin structure (with the styro as a core.) This added considerable stiffness to the wall surface itself, which may account for the increased transmission loss.
Stagered studs have pros and cons. It minimizes direct transmission through the wall, but, with sheetrock on only one side of the studs the walls are not very stiff.
The wall's structural stiffness depends more on a short(er) length/height and larger depth of the studs (6" v. 4") than the stiffness added by the surface material -- unless that skin is stretched/stressed somehow. I think of a stud as a vertical beam -- you don't want it to bend as the sound wave applies pressure against it (via the drywall surface.)
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Nsgarch...I have built many 2X4 interior walls, and they are almost floppy until you get the sheetrock on the second side.
Eldartford -- Nsgarch...I have built many 2X4 interior walls, and they are almost floppy until you get the sheetrock on the second side.
Yes that is so, but it's mainly because the drywall adds a bit of a 'flange' to the stud making it sort of an "T"- or "I"-beam shape in cross-section. Better to use more nails/screws than the code requires too -- doing so helps create the stressed-skin effect I mentioned earlier.

In any case, the main feature of staggered stud construction is the 'decoupling' of one side from the other; I think the improvement in transmission loss far outweighs any stiffness lost by the studs not being double-faced.

If I were starting from scratch, assuming a new wall and 8 - 9 foot ceilings both sides, I'd do 2x4 staggered studs (2x6 plates) and see if that seems enough (before painting ;-) It it wasn't, I'd start adding more drywall. That usually does it.

What I'm saying is, in a typical residential setting, I'd start with the staggered studs, and add from there as necessary. Why? Try changing your mind after a regular wall is up and 'rocked! ;-)
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OK, I'm going to do something I've never done here publicly and state my credentials: I attended grammar school PS 101 Oyster bay and at the age of 19 I suffered a grave disappointment I wanted to go to college but they said I had to graduate grammar school first.So then with hard study I went to medical school at Oxford in England. But it was so foggy over there I got lost and didn't know where I was so I couldn't find my way back to class. So with that I missed a whole semester but I finally did graduate forty in a class of forty and became a doctor. I started a practise but I was so good at medicine I didn't have to practice it, I knew it. I now head a research team experimenting with and trying bringing to market a "dehydrated water" supplement for Olympic athletes but the draw back is to liquefy it you need "WATER". Well I am off {really off} so enjoy your evening all and back to the dry conversation about dry walls and such.
Staggered studs is the most insane thing I've heard from a construction standpoint. Not only would a building inspector frown on this, your electrician would kill you if you ever needed any work done. You couldn't hang anything in that room ever because you couldn't confidently find a stud? You can add extra studs at a staggered rate within your 16's, for that matter, you could even stagger steel studs within wood ones?

Yes, I've built clubs. 18" of concrete won't even stop the problems. Eldaford is correct that you should be 16" on center for studs, period. Keeping speakers from being mounted in any way to a wall will reduce the bass transfer.

Doubling the interior drywall helps. Make sure you tape and mud the first layer, then hit is with a second layer. Stagger the drywall seams and not only screw but also glue the first layer to the studs. Ideally if money, time and space didn't matter, I'd build a double wall with the inside wall completely decoupled from the outer wall, built on rubber seams and a false ceiling too-this is only a pipe dream.
L, If you are considering 12 inch center framing, you are on the right track. 2 layers of 5/8 works wonders. Do stagger the joints in both directions. I use 6 inch acoustic insulation in 3 1/2 framing. Also works wonders. You do need both sides of this wall sheetrocked. 1/2 on the other side is fine. Hold the board 1/2 off the floor and 1/2 down from the lid, then fill this void with acousical sealant.
Schipo, I always tell people that every medical class has someone who graduated last, and that person just might be THEIR doctor.

Anyway, builders of townhomes with shared walls often put a "double" or "staggered" wall between units to minimize sound transmission.

If you put some fuzzy stuff between the studs, companies such as Roxul or Corning make insulation with sound absorbing properties. You can find it at Home Depot.

Also, I've never seen it in a store, but on some home reno shows on HGTV, I've seen a new type of sound absorbing drywall. It's a bit expensive. I believe it has a sheet of metal sandwiched between layers of gypsum. It might work through the stiffening effect that Nsgach noted. Maybe you can find it somewhere. Try the websites for drywall manufacturers.

Eldartford is correct about the styrofoam stuff having to be covered to avoid fires. I'm finishing my basement and I'm looking at adding styrofoam or polystyrene panels on the wall as a thermal break and for insulation. The panels all say that they need to be covered with something because they are flammable. The building code where I live requires covering as well.

I'm not smart enough to go to MIT. Maybe some of what I'm saying is true anyway.
One of the principles of reducing sound transmission through a wall is to add mass. Unfortunately, walls are already heavy, and to make a big improvement you have to add a lot of mass.

According to the greengluecompany.com which has done these kinds of tests in independent laboratories, "to improve sound isolation by about 10db you would have to quadruple the number of drywall layers on your wall - from one each side, to four on each side." Adding mass combined with other methods is far more effective.

I suspended a ceiling consisting of 2 layers of 5/8 drywall with Green Glue in between and suspended on sound clips, and achieved over 35 db reduction in sound in the room above. I highly recommend you read the their entire web site before making your decision.
Staggered/double studs plus 2 layers of super-dense drywall (Firewall) both sides as well as fibreglas internal insulation will give the best sound-insulation for the adjoining room. This sound-insulation is called STC (Sound transmission Class) Rating. Compared to a normal drywall with say 37 STC rating, the described wall can double the sound-proofing capabilities up to 60 STC.
STC Ratings
Study Diagrams
I've been seeing ads from a company offering rolls of sheet vinyl. They suggest covering your inner walls with the stuff prior to covering with sheet rock.
Sounds good to me...
Correction.....I am getting old!?
STC Ratings are in Decibels (dB) and thus are logarithmic.
Therefore the improvement of 37STC to 60STC is more than a TRIPLING in acoustic performance.
Good best for isolation is to STAGGER the studs. also, most code is 16" on center. There are various products to weave Between the studs as damper. DO NOT use styrofoam. It is toxic as hell when it burns, and probably against code. The products I have seen are Very heavy plastic.....I have no idea how they do it, but this stuff is pretty heavy, providing mass while meeting burn/self extinguising requirements.
By staggering, you DeCouple the walls 'sharing' the studs.
Just looking up, Elvick calls it 'insane'......Nope, just 'sound' engineering. pun intended.
Magfan, I totally understand the "sound" engineering. However, having renovated many buildings, I know what it's like to have to open up walls to search for studs. That's why I'd push for either 16" studs with random in between or at least a pattern to aid in future finding of the studs?
If I was buying a property with random studs this would greatly devalue the property and would be considered a "knock" down on any wall unless plans were available with exact dimensions and proof of proper construction by a qualified contractor.
Also, I've never seen it in a store, but on some home reno shows on HGTV, I've seen a new type of sound absorbing drywall. It's a bit expensive. I believe it has a sheet of metal sandwiched between layers of gypsum. It might work through the stiffening effect that Nsgach noted. Maybe you can find it somewhere. Try the websites for drywall manufacturers.
Markphd 02-07-09
Quiet Rock, 545 THX
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Elevick...When working on a 200plus year old house (like mine) studs are where you find them. Often they are rock hard hemlock that you can hardly get a straight nail into. Makes life interesting.
Lots of advice, thank you all. I'll probably stick to my original plan although that quietrock does look very intriguing..
-I might add a layer or 2 of the heavy gauge tar paper to the inside edge of the studs to add a little cushioning/isolation before I screw the double drywall to them. I've been caulking all the seams between ceiling and walls, then I'll do floor to walls too. I'm hoping the Green Glue is very effective between the drywall. Thanks again.
Lissnr,

Did you check out the QuietRock 525? One layer of the 5/8" thick 525 is equal to 8 layers of standard 5/8" sheetrock.
Jea48, I just checked out the QuietRock 510, which is $$$ less than the 525 (it's 1/2") and looks very good too. It's said to be 4-6 times better than double drywall and only a couple of STC's less than the 525. 1/2" won't be to "fire code" though, as compared to 5/8" which is. It's in a detached garage... should that be an issue??? (No bathroom, bedroom, or anything... just a "Hang-out" room).Thanks, Grant
Elevick, You completely misunderstood my post.
by 'stagger' I mean that there are 2 sets of studs, not studs at random intervals. Both sides of a dividing wall are NOT attached back to back on the same set of studs. This will couple them 100%.
Instead: try building 2 half-walls back to back. Total thickness should be maybe 6" using 2x4 studs. 1 set is covered by sheetrock facing room 'A'. A second set of studs *between* the first set and offset about 2" are used for the 2nd wall, being room 'B'. Weave a dense sound insulation/damper BETWEEN the 2 sets of offset studs.
The 2 walls are now decoupled..bass and have insulation between them...for HF.
BOTH walls will be 16"oncenter, but offset 8"......
Man, I wish I could attach a simple drawing!

Here is a picture of staggered stud wall construction.

Wall Picture
You need to get a good book and practical advice on construction for sound isolation. It is a complicated subject. Also, check out the following site for helpful advice:

http://www.soundproofing.org/index.html
Construction and insulation are most often left to idiots that build homes costing hundreds of dollars to heat or cool. Look to green building practices because they tend to match audiophile needs. Good houses are solid (Thermal mass), sealed, highly insulated from the outside, quiet, efficient and comfortable. Some can have highly integrated electronics that monitor heat and cooling systems. Most need active ventilation systems to bring in fresh air.
If you're not familiar with vapor barriers it's important to learn more or consult with a professional. Mold loves ignorance!
Magfan, great concept now that I understand you. That makes much more sense. It will take some talent to build...