Author Topic: No choice but to triple leaf?  (Read 8679 times)

subhunter

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No choice but to triple leaf?
« on: August 11, 2012, 04:18:05 AM »
Hi there,

I had an 11' x 13' drum room / rehearsal space built in my basement a couple years back. I basically used Green Glue on the inside of the room in between 2 layers of 5/8 drywall as I wanted the least destructive and space eating option possible. I didn't want to tear down 3 of 4 walls to keep costs down and being in a detached house I was only concerned with soundproofing my room enough so that relatively quiet band rehearsals and drum practising would not interfere with my family's down time in the evenings.

When the contractor I hired got to work on installing the drywall ceiling, I came home from work one day and noticed that he had put up almost one complete layer of drywall while the resilient channel I wanted installed under my joists before the drywall was to be hung was still sitting on my basement floor. He said his intention was to install the resilient channel in between the two layers of drywall... Obviously a lack of clarity and communication on both our parts. Knowing a bit about the triple leaf effect, I suggested that he just continue working without incorporating the resilient channel into the build and I crossed my fingers that the Green Glue in between the two layers of 5/8 drywall would already provide enough soundproofing regardless of the lack of decoupling.

Although I have pretty much achieved my goal of low volume rehearsing with my bands and the occasional low volume drum practising without waking my 2 year old son 2 floors up while he sleeps at night, I still find that there is a considerable amount of low frequency booming coming through the ceiling into my dining room above which is adjacent to my living room where my wife watches TV. Ideally I would find a solution that would allow me a little more volume headroom while turning the usual volume level down even more for my family. BTW, there are no ventilation issues.

My question and concern is how much of a positive or negative difference would it make if I was to add Genie clips to my existing ''soundproofed'' ceiling (I know where the joists are), a hat channel and then some Quietrock for example for added soundproofing and decoupling while lowering my ceiling the least amount possible. This would essentially make the ceiling the only surface that is de-coupled in my room similar to what my original design intended but from my understanding would create a triple leaf effect. My other option would be to rip out my ceiling to expose the joists and then build a decoupled ceiling EXACTLY like my original design intended.

Any insight and answers would be greatly appreciated!




Randy S

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Re: No choice but to triple leaf?
« Reply #1 on: August 15, 2012, 10:34:47 PM »
That is a very good question...I would say that as long as you fill the void between the new clips and channel you might end up with a good result.
Randy Sieg

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subhunter

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Re: No choice but to triple leaf?
« Reply #2 on: August 19, 2012, 12:13:40 AM »
You mean fill the new decoupled gap with insulation so that there is some absorption? The air gap between my existing damped ceiling and the floor above is that of a standard joist thickness, so 8'' I believe. The 8'' joist cavity is already filled with two layers of Roxul safe & sound. I know now that the second Roxul layer doesn't make much of a difference, my contractor suggested putting it up there when we realized that I had bought more than my build required. Point being is that I do already have a decent sized air space IMO and the existing damped ceiling so what would adding an additional decoupled damped layer do for my resonant frequency and additional soundproofing? Thanks again, much appreciated.

whatismisophonia

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Re: No choice but to triple leaf?
« Reply #3 on: August 19, 2012, 11:34:16 PM »
Correct me if I'm wrong, but I believe that the triple leaf scenario would hurt your soundproofing (at lower frequencies) ONLY if your current air gap were divided up into multiple spaces; however, if instead you are adding a second air space with a third leaf to the bottom of your current air gap, you should see at least some reduction, though even by decoupling I don't know that you would get much improvement at the low frequency resonance.  Below the resonance the wall vibrates as one mass unit in spite of decoupling; the same resonance which you are attempting to limit by decoupling.  It almost makes me wonder if you wouldn't do just as well to add another layer of drywall and greenglue, since a solid layer seems to be better for low frequency. 

However, there is also the fact that if you create a decoupled space and attach a single layer of quietrock, you would not only have the extra damping, but also a 1:2 differential thickness ratio from the third leaf to the second, which could help with your low frequency issues as well.  If you do decide to go with the hat channel and clips, report back with the results; I'm curious of how it would turn out.

johnbergstromslc

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Re: No choice but to triple leaf?
« Reply #4 on: August 19, 2012, 11:46:08 PM »
Nah, tear the sucker down!  Bite the bullet, spend a little extra money and fix it to the correct specs, instead of 'bandaid-ing' over your dipsh*t drywall guy's crap work.

Full insulation in the joist cavities, SSP clips, hat channels, THREE layers of 5/8" drywall, then seal the hell out of it. 

Don't worry about the weight - SSP clips + hat channels will handle it, far better than normal resilient channel.  If you want any hope of killing the low frequency noise through a wood-framed structure, this is what I would recommend.

whatismisophonia

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Re: No choice but to triple leaf?
« Reply #5 on: August 20, 2012, 12:19:51 AM »
Considering you can bear the expenses, J.B. is right:  Your decoupling would be in the right place to allow for a thick, solid, and damped ceiling + only one air gap, which would be an even larger space than what you've currently got to help aleviate the low frequency transmission; and depending how thick your floor is, you may also have a differential thickness going on as well.

subhunter

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Re: No choice but to triple leaf?
« Reply #6 on: August 21, 2012, 01:19:52 AM »
Wow! You guys are amazing! Thanks a LOT! My gut feeling also tells me to rip down the existing ceiling and start again properly from scratch. During my initial planning and purchasing stage, I thought the sound clips were not going to get me that much more soundproofing results than a resilient bar and were much more expensive for my budget. That was then, this is now... I know that the clips would be my best solution and I'm now ready to spend the extra cash. I'm also somewhat understandably kicking myself a bit for being cheap and less informed in the first place. It's so true that going the cheap route can often be more expensive in the long run... I honestly and obviously counted on the results from the non-decoupled ceiling ''mistake'' too much and my kick drum's low end too little ;). Got a 2 year old now and eventually another on the way... I don't want that to ever keep me from playing my music...

OK, back to business:

Here's a link with a good method to soundproof your ceiling from your overhead neighbour where you green glue an additional two layers of 5/8th under the floor above in between the floor joists. (Solution #5 - http://www.soundproofingcompany.com/soundproofing-solutions/soundproof-a-ceiling/). I'm hoping/wondering if I can somehow bring down my existing ceiling in strips so that I could employ this technique for additional soundproofing and somehow make use/reuse some of what I've invested/built already. Although the method described is to reduce the sound and impact noise coming down on you, mine would be the opposite but I imagine it would still make a difference, especially if I can pull it off relatively easily. A concern of mine would be if my floor joists would have any problem holding up these strips along with another decoupled three layers of 5/8. My second concern is potentially damaging a joist or wiring during the process. Although it's clear that I would only have to set the saw to cut to just over 1'', I also have a wood furring strip under my joists that my DW is screwed into giving me a little more headroom. Also, with most of my wiring going through the joists already, I'm less worried about damage during the ''strip'' take down as I am about my joists being able to hold up considerable extra weight once version two is put in place.

Another concern: would it really be worth doing all this considering my walls are not decoupled and that they are essentially (only?) two layers of 5/8ths with GG in between?  I imagine overall volume level would go down on the floor directly above and less-so general structural vibrations but how much closer would it get me to say playing at a ''stage'' volume while keeping things as noticeable as they are presently while playing at a relatively low volume? Sound would still have to go through the floor once if gets through my walls... I might only change my weakest link in doing so (like ventilation?) which may not be that bad...

Lastly, what's ''differential thickness'' all about? My guess would be how two different thickness layers will block/absorb different frequencies and how this could be beneficial. I believe the floor composition above in my dining room is a layer of sub-floor, a layer of parquet-style hardwood flooring and finally a layer of ceramic tiles on top. I believe this is correct and also that the ceramic tiles were therefore installed incorrectly, which probably explains why the grouting needs to be redone and why certain tiles have cracked under high traffic areas. This is how I bought the house, it's not my doing... the previous owners did a great reno job in general but cut corners in some respects. The flooring in my drum/jam room is carpet + under-carpet on the concrete slab if that requires any consideration at all...

Thanks again guys! You really rock!

whatismisophonia

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Re: No choice but to triple leaf?
« Reply #7 on: August 21, 2012, 04:04:16 AM »
I have very extreme reactions with certain very common sounds which I am unable to tune out as background noise; as a result, I've spent considerable time studying soundproofing, though I don't have much hands on experience.  I'm no bonefide certified soundproofer by trade, I'm just trying to understand it as you are, though I can at least give unbiased answers. 

I had actually thought of the idea of reusing old sheetrock just as your info shows, since I generally don't have enough money.  Figured if I cut out my old drywall along the inside edges of each stud and along the sill plates of my walls, I could remove the drywall in panels, reattaching them with greenglue to the opposite interior sides of the drywall on the other side of the wall and seal up the edges against the studs with acoustic caulking.  This all would work fine and dandy, though there were some reservations.  First, for the cost of one layer of green glue, I was thinking it would be less efficient than adding a solid unbroken layer to the receiving rather than source side because if attaching to the source side, there would be no glue or extra drywall where the studs met the wall.  And since the studs are pathways for sound, I figured it would be a waste to put it there, that is, if I were only to do a single layer of damping glue for the whole wall.  However, if you don't mind paying for extra glue, it would be useful to have both wall leaves damped.  The second issue is the fact that you are reducing the total depth of your air gap by adding mass to the interior.  However, especially with a damped panel plus the fact that your air cavity is already quite deep (the drywall isn't terribly thick either), you should have a net gain.  Beyond that, you could always just leave the thin strips of drywall attached to the studs/joists after you'd cut out the panels and attach the res channel/clips (with longer screws) over the top of the strips in order to keep the same air gap.

Moving along, considering that you set your saw no deeper than the total thickness of your combined wallboard, I wouldn't worry about damaging the studs or wiring.  If you're doing the work yourself though, do get someone to help support the panels so that they don't come crashing down on you. 


whatismisophonia

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Re: No choice but to triple leaf?
« Reply #8 on: August 21, 2012, 04:29:29 AM »
Part II:

As far as support is concerned, I have a carpentry book that shows joist and rafter spans for a given width; if you tell me how wide your room is, how wide your joists are (2x6, 2x8, etc.), and how many inches on center they are, I can tell you if you have more than enough support for extra weight.  If you might need extra support, one thing you could do would be to glue and screw 2x4s flatly to the underside of your joists along their lengths to create inverted T beam-like joists.  Your joist would work essentially as I beams, with the floor functioning as the top flange to resist compression, and the 2x4s functioning as the bottom flanges to resist tension and twisting.

If you're wanting to play fairly loudly, something should probably be done with the walls.  The best idea is to start with the interior of the wall, and work your way out.  Because you can always add greenglue after res channel, but not before, if I were you I'd cut out the wall as with the ceiling and use the channel you already have on the studs (if it's rc1).  You can just do a single layer of drywall on the channel and add more later if necessary.  Cost should be pretty low if doing it yourself, though time consuming.

The differential thickness I was talking about has an effect because of wall rigidity I believe.  Thicker walls are more rigid, and as such, resonate slightly differently at various frequencies.  As such, if a wall is built with varying thicknesses, it is more difficult for the wall leaves to resonate together.  The info I have shows that this effect seems to be mostly noticeable in windows with their thin stiff glass panes, and less noticeable in walls and floors; so it may not make any difference in your scenario.

And finally, if there is no reinforced bed of cement for your tiles to lay in, that would suggest why the grout is cracking; to much movement between the tile and wood floor.  You would need to remove the tile and either sand and finish your hard wood floor, or lay down some cement backer board and re-tile if that’s what you want.  I have a background in construction, so I know at least a little about it.  Also, if your joists and the spaces between them are made to support better, your grout will be less likely to crack as well.

subhunter

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Re: No choice but to triple leaf?
« Reply #9 on: August 22, 2012, 12:25:54 AM »
I probably wouldn't be doing all the work myself. I'd hire someone with the efficiency, time, tools and experience again and I assist where I could, especially in the evenings after I'm home from work and my boy is in bed.
 
Just to re-clarify, my walls are treated with essentially 2 layers of DW with GG in between, just like my ceiling. No surface is decoupled at the moment. The only difference between my ceiling and walls is that there are absolutely no holes in the ceiling surface for electrical outlets/lighting/heating/vetilation/windows/doors/etc and between my joists I've got 2 layers of Roxul + wood furring strips underneath them that the DW is screwed into. I didn't want to decouple the walls because I didn't want to lose more space and spend more money nor feel like it would then be necessary to purchase and install double doors bring up my costs even further. I essentially have one ''double gasket'' door consisting of a solid MDF door with a slightly larger 1/2'' MDF stuck to it with GG in between for both my doorways. My door frames essentially create two gaskets around the door and then the panel to keep things as airtight as possible. I even recently added an extra layer of Sonopan on top of the MDF panels since I had most of the supplies still lying around...
 
Although the overall volume level is higher on the other side of my walls, it seems considerably more ''bassy'' directly above in my dining room. This ''bassiness'' is what I want to reduce by possibly removing my damped-only ceiling and adding a heavier, decoupled ceiling. But, I don't want to do it in vain and subsequently notice after all the work that it hasn't made all that much of a difference after all that extra time, effort and money. I understand that theoretically I should increase the STC and other stats of the actual ceiling, I just want to make sure that my walls will be containing the sound enough and that it won't simply flank up the rest of the house through flanking channels to nullify any gains... Maybe I'm best to wait until I move and build a new room from scratch... I'm no hurry, but I believe that chances are that I would redo my ceiling before moving... Moving wouldn't be for another 10 or so years at the earliest the way I see things today...
 
So my joists are exactly 2 x 7 - so I figure that's really 2 x 8 - with 15'' OC. My room is about 11' x 13' in a basement corner of my house, therefore two walls are up against my foundation, one leads to my furnace room and the other the basement family room. I believe the ceiling soundproofing solution link I provided would haven't recommended such a solution if they thought standard joist builds wouldn't be able to handle it... And thanks for the confirmation about my main floor ceramic tiles!! I think I may one day replace a lot of the tiles with hardwood flooring, that way I may not have to raise/lower the mouldings and won't have to have the cement bed installed...

whatismisophonia

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Re: No choice but to triple leaf?
« Reply #10 on: August 22, 2012, 03:29:15 AM »
If you're only using rc1 channel, they're cheap and we're only talking an extra fraction of an inch; you probably wouldn't notice the change.  You don't need to have a double door setup, and in fact, you probably couldn't really do that anyway if you were only going with res channel.  Hat channel and clips, maybe.  You'd have to create a rough door frame from 2x lumber and attach that with metal L brackets through the sheetrock and into the channel to create an opening for the second door.  Also, if you do decide to sheetrock over rc1, make damn sure your handyman knows how critical it is not to short circuit the channel by zipping a screw through the sheetrock, though the channel, and into the studs.

Your doors seem ok, though your biggest problem will always be your seals.  I had double seals on my door, and there was a slight difference in isolation; but since the seals never really seal air tight no matter how hard you try and are the thinnest parts of the door setup, you might invest in heavy duty neoprene jamb seals (you could always take this stuff with you if and when you move).

I would assume that the "bassiness" in your ceiling pared with the overall loudness of the sound through your walls is a result of the air gap in your ceiling being larger than that in your walls.  The larger the air gap becomes, the lower in frequency the resonance moves.  That and the fact that the thicker gap in the ceiling is reducing the mids and highs so that you are mostly hearing the lows.   Mass+damping is your best friend here, though you should still decouple since you're probably playing a variety of frequencies.  That and the fact that decoupling seems to lower the resonance a bit because it shifts the structural resonance closer to the spring-air resonance (vibrations have to move mostly through air and insulation).  The idea is that if you can't destroy the resonance, either alleviate it with damping and mass or lower it below the threshold of hearing.

If the joist are southern pine, you're looking at around 13' (give or take depending on quality) for all rooms except sleeping rooms and attic floors, which can have an extra foot of span.  For Douglas Fir-Larch, Douglas Fir-South, and Hem-Fir it's more like 12' at average quality.  All of this is based on a 10 psf dead load (loads that won't move, such as flooring and sheetrock).  And if your joist are spanning along the short 11' side of the room as opposed to the 13' side, you certainly don't have anything to worry about.  When you remove the ceiling, inspect the joist's quality by observing how straight the grain runs; if it's full of splits and knots and the grain looks like it came from Dr. Seuss’s mill, its low quality.  If this is the case, and your joist are running along the long side of the room, I'd worry.

 

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