John Sayers’ Recording Studio Design ForumAn archive of johnlsayers.com, 2003–2022

Exterior wall, width limited. What do you think?

Started by marathon on 28 October 2004. 35 replies. In the Library under Walls, floors and ceilings.

Originally posted at johnlsayers.com, topic 2568.

marathon
Hi, all. I've really appreciated this resource. This is my first question; hope it's a good one, and I hope to offer good input soon. I'm building a garage with studio in the back; new construction. Studio is based on the one-room design from EQ magazine's Sept 04 issue. Due to local restrictions and the need to fit cars in the garage, I'm unable to do a staggered stud wall, or double wall with air gap. I can do a one-wall design. Three of the walls are exposed to neighbors. I've planned a 5 3/4" thick wall, and probably need to stick close to that width. What do you think of this plan? Could I do better (cost, materials, STC, etc.)? Is there something stupid here? Am I (or are the neighbors) going to be particularly vulnerable to a certain kind of sound trouble? Item, Thickness, STC, Mfgr, Model # Exterior Sheathing: 1/2”, in wall, Celotex, Premium Insulating Sheathing Stud Wall: 3 1/2", 35, 2x4, 16" OC Insulation: -, 4, Owens Corning, QuietZone [R19 instead? Exterior wall] Resilient Channel: 1/2”, 3.5, Auralex, RC-8 Sheetrock: 1/2", in wall Sound Barrier: 1/8”, 27, Auralex, SheetBlok Wall Board: 5/8”, 18, Quietsolution, QR-530 Total: width 5 3/4", STC 87.5
External image, not preserved — original: http://www.marathonrecords.com/Wall_Detail.jpg
Thanks a million for any input! - Jeff
cadesignr
An STC of 87.5? :shock: :shock: I don't think so. Where did you get these ratings for this wall? 35 for wood studs...... :? How do wood studs get an STC rating? fitZ
marathon
cadesignr wrote:
An STC of 87.5? :shock: :shock: I don't think so. Where did you get these ratings for this wall? 35 for wood studs...... :? How do wood studs get an STC rating? - fitZ
35 STC is not for the studs, of course; it's for the section of wall construction up to that point. I'll go through my notes to find where I got that element of the total, and list it here. If the overall STC listed looks way out of line to you, do you have an idea of what would be a more sensible assessment, or a more realistic total STC for this design? i.e., do you perhaps have a helpful comment? I'm not trying to have this handed to me on a silver platter; I'm doing whatever research I can - but I'm a neophyte. Nothing I can do about that other than what I'm doing, which is trying to learn more from whatever resources I can find. And this message board is clearly chock full of knowledge and experience. If you have something instructive to say, I'd really appreciate that, rather than something dismissive. Many thanks.
knightfly
Jeff, you can't just add 35 dB and 25 dB and get 60 dB; the decibel is a logarithmic ratio, so you first have to convert to a real ratio, then combine, then re-convert back to decibels. Here's a basic idea of how this works; http://www.safetyline.wa.gov.au/institu ... l54_05.asp Also, you can't just add (even doing it the hard way) decible values for each material in a wall and expect to get close to a real STC value. A wall becomes a system, and each component of the system adds or subtracts from the whole in different ways and at different frequencies. In actuality, the wall you show would likely come in at around 50-53 dB STC, with a mass-air-mass resonance of around 79 hZ, and the Transmission loss at the low end of the audio spectrum would run around 25-27 dB, due to the high resonance. This can only be improved by wider distance between inner and outer leaves, higher density insulation, and more mass in each leaf. On top of this, I'm not sure which Celotex product you're referring to but the versions of this I'm familiar with aren't a very high mass material, and should NOT be used alone (or even with other materials) for sound walls - Here's a page that explains most of this better than I can - http://www.domesticsoundproofing.co.uk/tloss.htm I hope this gives you a better idea of how this stuff works... Steve
cadesignr
Hello Steve, I have a question regarding the LAST partition illustration, the one with an STC of 63. I wonder if this illustration is based on both plates being on the same surface? If so, I wonder if this STC increases if one is decoupled from the other on a floating floor? I mean, WHEN they tested these, it would seem they would be on the same floor, correct? :? Also, let me offer an apology Jeff, if my question seemed condencending or offensive. It wasn't intended that way. I was just .....well, shocked :lol: I have never heard of a SINGLE wall with this high of an STC rating, and was sincerely interested in where that came from, as I am familiar with the illustration on the link Steve posted, and your total STC seemed to suggest an error somewhere. I had thought of that illustration, but couldn't remember where it was located to link it, and I am NO expert at this stuff so I didn't have anything constructive to offer either. Sorry. fitZ
Michael Lee
What do you think of this plan? Could I do better (cost, materials, STC, etc.)? Is there something stupid here? Am I (or are the neighbors) going to be particularly vulnerable to a certain kind of sound trouble?
I am drawing the plan for Marathon and guessed at the STC rating for the wall to be 35. I'm probably a little high but I couldn't find a detail showing 1/2" celotex exterior sheathing, stud, then 1/2" interior drywall. We have wall width constraints of 5.75 inches and are looking for the best system for the best price to fit into those dimensions. I've enclosed the section detail for the entire room. Before continuing with the drafting, we want to be certain we are providing the best isolation at the lowest price. QuietRock calculations based upon difference between standard sheetrock assembly and QuietRock assembly shown at http://www.quietsolution.com/constructi ... tions.html. 1# Vinyl STC number pulled from http://www.auralex.com/sound_isolation_ ... etblok.asp Resilient Channel STC number pulled from http://www.auralex.com/sound_isolation_ ... _Table.pdf. They actually show a STC of 7 but I took the modest approach. Insulation STC number pulled from http://www.saecollege.de/reference_mate ... 0Chart.htm. The chart for resilient channel actually shows a STC of 7. Again, I used the modest approach. Please let me know if the above information is factually incorrect and if so, please show me where. Anyone with constructive criticism (the type that adds information without just cutting down the design) is greatly appreciated. Michael Lee Draftsman
Image not preserved: 041029-3 Cross Section.JPG
Michael Lee
knightfly wrote:
Jeff, you can't just add 35 dB and 25 dB and get 60 dB; the decibel is a logarithmic ratio, so you first have to convert to a real ratio, then combine, then re-convert back to decibels. Here's a basic idea of how this works; http://www.safetyline.wa.gov.au/institu ... l54_05.asp
Also, you can't just add (even doing it the hard way) decible values for each material in a wall and expect to get close to a real STC value. A wall becomes a system, and each component of the system adds or subtracts from the whole in different ways and at different frequencies.
Accoustics is a learning process for myself also. I appreciate your assistance and will research this further. If you could look at my assembly and let myself or Jeff know what products could be considered to make a significant difference without running up cost, it would be appreciated. The dimension of 5-3/4" is all we have to work with for wall depth. No more. The reason for the Celotex is that that is an exterior wall and structural sheathing is required. We could use OSB or CDX plywood but from what I've read, the Celotex has better properties for sound dampening then either of the others. Again, we are in the idea gathering stage so any help is appreciated. I'll study the links you have provided. Again, thank you. Michael Lee Draftsman (and complete accoustical novice)
Michael Lee
Lesson learned about STC ratings. I'm gonna drop them. The simple request is based upon this drawing, what can be done to improve the rating without running the cost way up. Any and all suggestions for improvement greatly appreciated. Michael
Image not preserved: 041029-4 Cross Section.JPG
marathon
cadesignr wrote:
Also, let me offer an apology Jeff, if my question seemed condencending or offensive.
Thanks much for saying so, fitZ, even though it's not really necessary. I think I was just eager to see that someone had posted a reply, and I shouldn't have been thin-skinned when it was hinted I might not know what I was talking about. ... because I'm definitely on the steep part of the learning curve. Steve says the current wall design likely comes in around 50-53 STC. I'm now also looking to see whether I can find documentation discussing what STC rating would make for an acceptable backyard studio. i.e., what STC should I try to achieve in order to not have the cops called if I'm working at 10:30pm? And is that going to be possible with a single 5.75" wall design? The neighbors will be (very rough estimate) 30-40 feet away.
Michael Lee
Along with the section plans I think it might help to understand the restrictions placed on the project. We have a 700 SF total requirement and have to include a 2-car garage in the design. See attached sketch. The shape of the studio requires front wall to be 11', back 15', length to be 21' and height to be 8'. All dimensions are in the interior finished requirements. Michael
Image not preserved: 041029 Floor Plan.JPG
cadesignr
Hello Jeff and Michael. Say, I have a question regarding the building. Is this a NEW addition to the house? Reason I ask, is you mentioned that the Celotex is required for structural reasons. This must be for shear, correct? From my limited knowledge, Celotex seems like a really weak panel for shear resistance, although I am NO expert. And I'm a little bit confused in the first place. If this is new, has the Building inspection department OK'd Celotex for a shear wall? Or can't you use 1/2" ply as the shear panels on the outside? And if it is existing, wouldn't it already have shear panels on the outside if the interior were unfinished and were required in the first place? :? Another question. Is the vinyl layers under the plate as a moisture barrier? BTW, from your drawing, it looks as if this is a unattatched freestanding building, correct? fitZ
marathon
fitZ, I can answer the most basic of those questions: :) Yes, this will be new construction, and a freestanding structure. This is why I'm concerned with the STC attainable by a single wall design of such limited width - because whatever gets through those walls is getting to the neighbors. - Jeff
Michael Lee
This must be for shear, correct? From my limited knowledge, Celotex seems like a really weak panel for shear resistance, although I am NO
Structural sheathing consists of products like 9/16 OSB, 1/2 plywood, 1/8" thermoply (which I don't like at all), and 1/2" Celotex. They all perform the same basic function of keeping the building from racking. The Celotex breaths a lot better than the other products (perm rating of 20.0 vs 2.0) and considering we are basically sealing off the inside with a vinyl sheet, I think breathing will be important in case of trapped moisture. Plus, I think there will be less vibration transfer than with plywood or OSB (in my less than knowledgeable opinion). Certainly, Celotex is likely structurally weaker than the plywood or OSB but I believe the benefits outweight the deficiencies. All meet code and Celotex has been around a long, long time with no record of structural failures that I am aware of. The vinyl under the plate was a recommendation on one of the acoustic sites to help isolate the stud. They show it at the top and bottom (yea, I forgot to draw the top). Likely, the building department won't like it and I'll have to change it to foam but I'm willing to give it a try. It's the same vinyl material used on the vertical surfaces. If you know of any other structural sheathings or other product ideas we could use with better properties, I'm all ears. Just direct me to the nearest hyperlink and off I go... The structure is a completely new construction, detached garage & studio. If you need any more information, please let me know. Michael
Michael Lee
One thing I found in my research is that rock wool is a lot denser than FG insulation. Is the rock wool worth the investment in terms of getting any significant return for the dollar?
PhiloBeddoe
I am not an authority on any of this stuff but my advice is that you may want to reconsider the Quietrock, or at least how it is being applied here. I'm not sure if you've priced it yet, but it's about $120.00 per 4'x8' sheet so it needs to be considered carefully. If you read a little more into Quiet Solution's pitch, their argument for purchasing the Quietrock is that it removes the potential of "short-circuiting" a resilient channel system by nailing/screwing directly through the channel into the studs or other failure modes. I believe this is a very valid concern, but you are suggesting the use of both Quietrock and RC which negates the benefit. I don't think any of their proposed wall configurations include RC. Also, if you look around this forum and others, you'll find some good opinions about mass loaded vinyl. I'd recommend shopping around if you decide to use it. Best of luck
cadesignr
The vinyl under the plate was a recommendation on one of the acoustic sites to help isolate the stud. They show it at the top and bottom (yea, I forgot to draw the top). Likely, the building department won't like it and I'll have to change it to foam but I'm willing to give it a try. It's the same vinyl material used on the vertical surfaces.
Hello gents and thanks for the reply Michael. Please forgive ,me for poking my nose into this thread and actually not contributing something, but this is how I learn. By questioning principles, techniques, and materials. I am a designer myself and have learned a lot here simply by sticking my nose in. :lol: As to your use of the vinyl to isolate the plate from the slab. Normal practice dictates the use of a "J" bolt embedded in the slab to hold the wall plate to the slab, but from my understanding, as soon as the nuts are tightened on these bolts...goodby isolation! :( I'd sure be interested in how you are doing this IF your not fastening the wall to the floor with J bolts. Unless I'm missing something here, which wouldn't be the first time. Hahahaha! As to the Celotex, that amazes me that it passes code as a shear panel. Isn't this the lightweight fiberous material with a white primer coat on one face that they used to call "soundboard"? Seems to me that I can break that stuff with my bare hands, let alone a racking building :roll: Go figure. They are the experts I guess, and it wouldn't pass code if it hadn't been tested. Personally, if it were in an earthquake zone, I'd be kinda leary though. Are you putting something else OVER this stuff. Seems like it isn't really weather resistant either. I've never heard of it use on an exterior, even under something like vinyl siding or wood siding. Hmmmmmmmm, maybe I AM confused :? :shock: Wouldn't be the first time for that either. :wink: fitZ
Michael Lee
their argument for purchasing the Quietrock is that it removes the potential of "short-circuiting" a resilient channel system by nailing/screwing directly through the channel into the studs or other failure modes.
From what I've read, the "short circuit" issue isn't shared by many. I'm certain there are some resilient channel products that are poorly manufactured that may have resulted in failure but I have a difficult problem beleiving that soooo many experts in acoustical sound would recommend the process if it was a complete failure. We are just trying to get above STC-55 without going much, if any, past 5-3/4". We have a layer of high density vinyl in between the QuietRock and the 1/2" sheetrock. I know it is expensive but I've not found anything with near the properties
Also, if you look around this forum and others, you'll find some good opinions about mass loaded vinyl. I'd recommend shopping around if you decide to use it.
Best of luck[/quote] Definitely, we will shop the vinyl. There's almost a 100% swing in price on that product from vendor to vendor. Thanks for the feedback. Once we get close to the STC rating we are looking for, we'll have to shop cost and make certain that project is in budget. After that, it's hard decision time. Right now, we just gotta get in range first and just don't have room for a staggered wall. Michael Lee Draftsman
Michael Lee
[ As to your use of the vinyl to isolate the plate from the slab. Normal practice dictates the use of a "J" bolt embedded in the slab to hold the wall plate to the slab, but from my understanding, as soon as the nuts are tightened on these bolts...goodby isolation! :( I'd sure be interested in how you are doing this IF your not fastening the wall to the floor with J bolts. Unless I'm missing something here, which wouldn't be the first time. Hahahaha!
Check out http://www.fabreeka.com/products/washers.htm for products that meet that need. Michael Lee Draftsman
AVare
So many points to comment on... Rockwool vs fiberglass: Check the prices in your region, including multiple manufacturers. Teh prices and difference are all ove th place. MLV and mass: What is needed is mass. IT has already been alluded to, but here it is in blunter words. I have never seen any acoustic testing data showing that MLV is better than any other product of similar mass. You have the space, go with gypsum board, HDF etc. You don't have space, go with sheet lead, still cheaper than Quietrock. Good luck! Andre
cadesignr
Hey Michael, thanks for the link. Interesting. I'm still curious though whether there is indeed decoupling once the nuts are tightened. But, it doesn't need to hashed over any further. I see you are a draftsman too. I was a detailer for a Store Fixture Manufacturer for close to 20 yrs. Still do it as my own business now. What program are you using in the pics? fitZ :)
Michael Lee
Sheet leads the one thing I haven't looked into yet. What I did find was that QuietRock is cheaper or as cheap as most 1/8" vinyl products. It's kinda like combining sheetrock with vinyl and getting a hybrid of the two. For our application, it was the best value to date to add lots of denisty in a small space. The QuietRock would be worth it if it would jump up the values in a small space and according to their docs, we might be able to achieve an STC of 57 using three sheets of 5/8" product. http://www.quietsolution.com/constructi ... tions.html Check out the detail labeled "Virtual Double Wall - QuietRock on both sides, double layer on one side". I'm figuring the QuietWood is comparable to the QuietRock in STC but have a message into the folks (closed on Sat) to find out. I appreciate the input about the lead. That had not come up anywhere I've looked. Michael
Michael Lee
cadesignr wrote:
What program are you using in the pics? fitZ :)
I use MiniCad. It's an older Mac program that does 2D & 3D architecturals but lets me save them in PIC format which I then convert to JPG and edit to a lower rez for repo. It works quite well for what I need it for. I got the MiniCad for like $60 on Ebay and a used PowerMac for $75. Elcheapo Cad setup that would have been state of the art back in 1996 or so. Certainly all I'll ever need. Michael
knightfly
A couple of ways to compare - note that the concrete wall has quite a bit better LF TL - about 6-7 dB @ 50 hZ. The low end is the hardest part on walls, so this is significant. When you consider that (do a google on Fletcher-Munson) human hearing threshold at 50 hZ is around 55 dB, if you have a TL of 33 @ 50 hZ you should barely hear anything thru the concrete wall until you're generating 85 dB at that frequency. Also note that these two examples, even though they are within one STC point of each other, will NOT have anywhere near the same isolative properties; the concrete wall will have nearly TWICE the effective sound isolating properties, mainly due to the LF performance. This does, however, assume that nothing else you do will "screw this up" - which isn't likely given some of the constraints you've stated or drawn. There is no single(commercial) door that will come close to this 55 dB spec that costs less than $4000 - check here http://www.overly.com/doorCo/Products/index.cfm for more on that. So you would need to allow for a sound lock and two doors in your plan in order to maintain good iso. Your ceiling will be another challenge; depth of air space would be your friend here, since you can't hang too much weight on skinny ceiling joists - the increased depth of joists will help both strength and widen the air gap; that way, you could use more layers of gypsum on either side of the ceiling joists AND get a wider gap; both of which will improve isolation. All the above comments are assuming you're starting from scratch; seems like I read that in earlier posts, correct me if I'm wrong. Given an 8 x 10 foot section of wall, in my area costs would run roughly $300 for the solid concrete (based on hiring it done - $100 for concrete @ $70/yd, $200 for labor - possibly more including forms, usually concrete contractors re-use these and may charge a portion of the cost to your job) - Materials only for the drywall version would run around $125 for the same 8 x 10 section, if you HIRE it done labor would run about the same; so, if you're NOT DIY it would be maybe a little cheaper for concrete. A "magic bullet" wall that thick might improve on some aspects, but I don't think you'd get any better LF performance than the solid concrete wall. All these are very expensive. Yes, they give you more mass in less space; but not as much as concrete, and the cost difference isn't insignificant; a single 4x8 sheet of 5/8 wallboard runs around $7, which, if it were MLV, would have about the same isolative properties; the cost of the MLV would run around $1.25 a square foot, or $40 vs. $7 - multiply this by both sides of the wall, and wow... One thing to consider; which is better, perfectly proportioned space that you can't use because of noise problems, or slightly smaller space that's usable 24/7? If you don't have any more space to expand your envelope OUTWARD, those are your two choices; even tho the "magic Bullets" approach like MLV, Quietrock, etc, may improve TL somewhat in a given wall thickness, I've yet to see any of them that are even close to cost-effective... Steve
AVare
A "magic bullet" wall that thick might improve on some aspects, but I don't think you'd get any better LF performance than the solid concrete wall
Total agreement Steve. You summed it up perfectly. On Quietrock etc walls:
What I did find was that QuietRock is cheaper or as cheap as most 1/8" vinyl products. It's kinda like combining sheetrock with vinyl and getting a hybrid of the two.
I have NEVER seen any test data indicating QueitRock etc is cost effective. Neither for any hybrid type either. Compare the prices with similar/equivalent systems from IR-761 http://irc.nrc-cnrc.gc.ca/fulltext/ir761/ and compare on thickness, paying attention to LF TL or concrete block walls from BRN-217 http://irc.nrc-cnrc.gc.ca/irc/fulltext/brn217/brn217.pdf and IR-586 http://irc.nrc-cnrc.gc.ca/fulltext/ir586.pdf Lots of data there, but it should help you significantly in decideing what construction to use. Have fun! Andre
knightfly
It sounds to me like you're talking about the same Celotex product I'm familiar with; I don't think this is a valid way to build considering the isolation you want and the wall thickness you're limiting yourself to; celotex isn't a high mass product, and having only that on the outer leaf of your wall will weaken the isolation considerably. Using MLV will agravate any moisture problems and help you grow mold - http://www.buildingscience.com/resource ... part_1.pdf http://www.buildingscience.com/resource ... part_2.pdf Here are predictions for two different walls within your parameters; note that the simpler (but NOT DIY-able) concrete one beats the other one by quite a bit - If you're going to use a mass-air-mass wall, I would use 3/4" OSB on the outside, unfaced insulation, preferably 3-4 PCF mineral wool, and two layers of 5/8 gypsum wallboard on the inside over Resilient Channel - the OSB has more mass than celotex and is stronger against racking - the wall I just described would have an STC of 60-61, with its low end at 25 dB @ 50 hZ, roughly. The concrete is still better... Steve
Image not preserved: ConcVsDrywal1.JPG