STC comparison wall on concrete vs wall on floating

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STC comparison wall on concrete vs wall on floating

Postby Bob » Sat Feb 14, 2004 8:42 pm

Hello:

Please have a look at
http://groups.msn.com/BobGoldsHomeTheat ... &PhotoID=1

There's a noise source in the middle, and two sample double wall configurations on the left and the right. The two wall systems are identical, except that the inner wall of one is on top of the floating floor and the other is not.

Which, A or B, will have the better isolation?

Essentially this is a question about whether the flanking noise through the floating floor will be greater than the noise generated by coupling the inner wall to the floor.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Bob » Mon Feb 16, 2004 5:31 pm

bump
Regards
Bob Golds
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Postby Paul Woodlock » Tue Feb 17, 2004 1:04 am

Greetings

All thing being equal ( natural freq, etc ), I wouldn't think there would be much in it.


btw - I don't think you'' need the RIC-1 decoupling the studs from the inner drywall. The studs are already decoupled at floor level

Furthermore, unless it was drawing error, the 3 drywall layers on the 50dB side of the walls should NOT touch the floor. Float them on the NAF-10 as well or leave a gap. Otherwise the NAF-10 is rendered useless.

Also consider disc cutting the concrete slab between the two walls. Make sure this is structurally safe FIRST :)


Paul
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Postby Bob » Tue Feb 17, 2004 2:07 am

Hi Paul

I've fixed the photo a bit
http://groups.msn.com/BobGoldsHomeTheat ... &PhotoID=2
The changes are that I put the drywall on the NAF-10 (3 places). The original photo is no longer there.

I figured that the RSIC-1 was a bit of overkill. I'm trying to make the wall both springy and massive. That's why I've also got 2x4 studs on the RSIC leaves mounted 4" flat side to the gypsum. Normally RC on decoupled studs is a waste of money, but RISC also has rubber. I've read that rigid walls make a room boomy. This room will only be 1800 ft^3. One layer of gypsum on the room side is recommended, but I also want the isolation and air tightness that two layers provide. So I've got the studs rotated 90 degrees and RSIC-1. It's an idea, not yet a plan.

The 'cutting the concrete slab' has been mentioned before. I understand the principle. The best way to apply it is to cut the cement floor on the 1.2 sides of the room that don't have concrete walls on them (i.e. one whole wall, plus 20% of another wall). But I'm not convinced that it's a good idea for a basement to have its slab cut, or that there's a lot of noise going through it. If there were a lot of noise going through it, then relative to everything else, cutting the slab is cheap.

All thing being equal ( natural freq, etc ), I wouldn't think there would be much in it.
I'm not sure what you mean by that. Did you decide on A or B ?
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby jcgriggs23 » Wed Feb 18, 2004 11:38 pm

1) I agree with Paul - the concensus is to use RC on one side of a partition only and that having it on both sides does not improve performance.

2) I'd guess that the difference in performance of either solution on the same, solid base is probably small - perhaps even small enough to be swamped by the uncertainties due to precise materials (real-world mass and damping) and construction. Assuming that someone has calculated the spring values for both designs properly, I'd go for the option that is easiest and cheapest to build

My $0.02 (Canadian),
John
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Postby Bob » Thu Feb 19, 2004 3:26 am

jcgriggs
1) the RC is only on one side.
2) "cheapest to build" sounds practical to me. I can't figure out which is better.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
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Postby Paul Woodlock » Thu Feb 19, 2004 3:28 pm

GReetings Bob

Just looked at your new picture.

The right hand version doesn't make sense to me. You got a wall rubber isolated to the studs, the studs rubber isolated t othe floating floor and then the floor rubber isolated to the original floor.

If you're building the wall on the floating floor then the KIP should be all thats required.

important question. Are you building a room within a room ( including ceiling )? Or alternatavily, what will happen at the top of the wall?

If it's a room within a room ( walls and ceiling built on floating floor ) then all you need is the rubber mounts under the floor.


Also, what about the other wall ( whre you've attached 3 layers of drywall ) IS this brick on NAF-10? If so it's highly possible the concrete slab will have to be thicker where this wall sits.



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Postby Bob » Thu Feb 19, 2004 4:08 pm

Hi Paul:

Thanks for the review. This is still just in the planning stages. There may be fewer layers of gypsum, or even changes in the materials.

I had thought the KIP was enough too, but you suggested that I add rubber under the gypsum on one side, so I thought I should add it under every piece of gypsum.

The top of the wall wasn't relevant to the question I was interested in, but obviously it's important to the room. The ceiling plan is to hang it on kinetics springs. To take the load of the ceiling I have to add more joists where the springs go, but they'll be bolted to the existing joists, sit on top of the foundation wall at one end, and the i-beam in the middle, and the 3-gypsum-layer wall on the other end. I have an I-beam that makes the placement of room-within-a-room joists on the floated walls somewhere between impossible and an engineering nightmare. i.e. I can build it, but it will fall down.

The 3-gypsum wall is attached to the ceiling joists. The 2-gypsum inner wall is not attached to the ceiling joists. The inner wall is a continuous floated box four walls.

No brick. With the earth under the concrete slab I didn't think I needed to worry about the weight of three layers of gypsum, 7.5' tall.

I thought this was obvious, but in case it's not. I'm building one double wall. I drew a left and a right room, each with it's own floating floor, just to save on .jpg files.
Last edited by Bob on Thu Feb 19, 2004 4:19 pm, edited 1 time in total.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Bob » Thu Feb 19, 2004 4:19 pm

Hi Paul:

Further to the KIP / extra piece of NAF-10 on the right hand side.
For sound getting out of the room this is clearly pointless, because the sound will touch both the floor and the wall at equal volume, so they may as well be coupled physically because it's cheaper.
But for sound getting into the room I was thinking there may be vibration effects through the concrete, and more isolation might make the walls a bit less of a drum to conduct the sound into the room. On the other hand, since the air space under the floor is the same air space as the in-between the double wall, it probably doesn't matter either (i.e. the naf-10 is not required).
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Paul Woodlock » Fri Feb 20, 2004 12:33 am

Bob wrote:Hi Paul:

Thanks for the review. This is still just in the planning stages. There may be fewer layers of gypsum, or even changes in the materials.

I had thought the KIP was enough too, but you suggested that I add rubber under the gypsum on one side, so I thought I should add it under every piece of gypsum.

The top of the wall wasn't relevant to the question I was interested in, but obviously it's important to the room. The ceiling plan is to hang it on kinetics springs. To take the load of the ceiling I have to add more joists where the springs go, but they'll be bolted to the existing joists, sit on top of the foundation wall at one end, and the i-beam in the middle, and the 3-gypsum-layer wall on the other end. I have an I-beam that makes the placement of room-within-a-room joists on the floated walls somewhere between impossible and an engineering nightmare. i.e. I can build it, but it will fall down.

The 3-gypsum wall is attached to the ceiling joists. The 2-gypsum inner wall is not attached to the ceiling joists. The inner wall is a continuous floated box four walls.

No brick. With the earth under the concrete slab I didn't think I needed to worry about the weight of three layers of gypsum, 7.5' tall.

I thought this was obvious, but in case it's not. I'm building one double wall. I drew a left and a right room, each with it's own floating floor, just to save on .jpg files.


Yes, it's quite obvious :) , and always was :)

If your'e putting a 2nd ceiling in why not just build it on the inner 4 walls that sit on the floating floor.

Then you'll have a proper room within a room. The only 'rubber' required then is under the floor. If you run the new joists parallel to the I-beam. then you can build the inner ceiling to 'box' around the I-beam. It won't fall down.

You should keep MASS- airgap - MASS, or MASS-rubber-MASS systems to 2-leaf. 3-leaves or more are worse than 2-leaves.

No brick. With the earth under the concrete slab I didn't think I needed to worry about the weight of three layers of gypsum, 7.5' tall.


Sorry my bad :) I can see it's studwork holding the 3 layers of drywall now. No it won't be a problem on the slab.

If you do the room within a room, and I think you could it's then questioanble whether you'll actually need the 3 gypsum wall to sit on rubber. but some lke Eric would be better to clarify this.


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Postby Bob » Fri Feb 20, 2004 4:16 am

If your'e putting a 2nd ceiling in why not just build it on the inner 4 walls that sit on the floating floor.


The span is 14' (4m). The concrete slab to joist height is 7'6" (230cm). The concrete slab to i-beam is 7'2" (219cm). The joists are 2x8's. Although a 2x6 joist can take the weight of 2 layers of gypsum dead load over a 14' span there are two problems
a) it's impossible to put a 14' joist up there (without removing the floor, or all the house wiring and plumbing and coming in from outside through an outside wall). An alternative is to cut it in the middle, and then try to join it back together in place. But I've been told this will not work and will kill people when the ceiling falls on their heads. Even if I made this thing out of 2x8's it couldn't be connected in the middle and still be strong enough.
b) The 2x6 has to be lower than the bottom of the existing 2x8's and not touch the i-beam. So my plan was to notch the 2x6 one inch so that it would be half an inch above the i-beam, and half an inch below the 2x8's. This I've been told is equilly foolhardy (in a structurally deadly sort of way). Generally speaking notches in the middle third of a spance are not allowed.
c) removing the intra-joist X bracing would make the existing floor weaker.

I had a bit of a conversation about this ceiling beam bit,
http://www.recording.org/cgi-local/ubb/ ... 4;t=001282
and the floor
http://www.recording.org/cgi-local/ubb/ ... 4;t=001293
(both of these threads held LOTS of useful information for me)

I can not move the i-beam without having the house cave in on itself.

So the best plan seems to be to use Kinetics springs to hold the ceiling up.

I'll see if I can draw a diagram of what I have in mind with the springs and the ceiling and the i-beam. And what I think is a cool idea for a polycylindrical on the bottom of the i-beam soffit.

Another thing that may be obvious or not. I'm the poster formerly known as Z60611. This forum is surfed a little less by email sniffers, so I'm using my name. ( Hello Eric ! )
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Paul Woodlock » Fri Feb 20, 2004 11:45 pm

Greetings Bob :)

hehe - it certainly wasn't obvious that you are(were) Z60611 :) :)

bugger - IExplorer just crashed - back in a bit
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Postby Paul Woodlock » Sat Feb 21, 2004 12:29 am

Greetings bob

I read the RO topics

So lemme get this straight? The I-beam sits in the middle of ceiling, and wooden ceiling joists at 90 deg, sit on it??

So you can't interleave inner room joists, becuase the I-beam is crossing their path?

That scuppers all my previous suggestions then. :)

I heard you talk of you inserting the new joists over the I-beam, but that would entail cutting them in half and joining up again. ( I'm trying to understand better here.. ) by this I presume the existing ceiling joists are sitting on top of the beam, and not wedged into the side of the I-beam, sitting on it's lower plate ???

however you seem only to have a 4" difference between the floor to I- beam, and floor to existing joists. Yet you say the I- beam is 6".

Bob can you confirm the exact delails of your ceiling construction?

I think I've come up with a solution which will avoid having to install joists OVER the I-beam, will hopefuilly avoid any notching of joists, and importantly will allow a truw room within a room, thuis saving on lots of hassle with floating ceilings, and multiple rubber decouplings at tops and bottoms of walls etc.

I'd have to draw out a plan in Autocad and mail you a piccie, as It's too complicated to describe, but the concept is quite simple. :)

Paul
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Postby Bob » Sat Feb 21, 2004 12:41 am

Hi Paul:

I'll throw together a drawing. After dinner.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Paul Woodlock » Sat Feb 21, 2004 12:58 am

Bob wrote:Hi Paul:

I'll throw together a drawing. After dinner.


Cool, soon as ya can really... It's 1am here. although I don't go to bed till 6am there's loads to do. I already made some drawings, so I can modify them if necessary when I get ya piccie.

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Postby Bob » Sat Feb 21, 2004 2:51 am

Hi Paul:

I've finished the first of two. (i.e. I have to do another one that shows the i-beam and how I'm building the real and fake soffit and pseduo-poly)
I also wanted to take some photographs, but it seems my digital camera's battery needs recharging. Oh, I see it's charged now so I'll give it a try.... The ibeam pictures are uploaded.

The joists sit on top of the i-beam, and on top of the concrete foundation walls on either side. The joists are 2x8s. The joists do not run from concrete wall to concrete wall. They run from concrete wall to the i-beam. And then another joist runs from the i-beam to the other concrete wall.

http://groups.msn.com/BobGoldsHomeTheatre/shoebox.msnw

The image that I just created is BobCeiling1.jpg
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Bob » Sat Feb 21, 2004 3:57 am

Hi Paul:

I've created BobCeiling2.jpg, and posted it at the above URL. I think that's it.

Oh, BTW, because the furnace is 2" to the right of the detached wall on the right hand side, that detached wall has to be built on the floor and lifted into place. That piece of blue up near the top is neoprine to make it air tight up there.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Paul Woodlock » Sat Feb 21, 2004 4:05 am

Bob wrote:Hi Paul:

I've created BobCeiling2.jpg, and posted it at the above URL. I think that's it.

Oh, BTW, because the furnace is 2" to the right of the detached wall on the right hand side, that detached wall has to be built on the floor and lifted into place. That piece of blue up near the top is neoprine to make it air tight up there.



check your private message..
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Postby Bob » Sat Feb 21, 2004 4:14 am

OK. My private messages says "You have no messages in this folder".
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
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Postby Paul Woodlock » Sat Feb 21, 2004 1:44 pm

Bob wrote:OK. My private messages says "You have no messages in this folder".


hmmm???

oh well. Can you mail me at paulwoodlock@creepers.fsnet.co.uk and I'll send back my idea


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