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Old 04-27-2010, 02:18 PM   #1
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Insulation with Sound Isolation Clips


]Hey All,
So here is the scenario:
I own a two unit building in San Francisco with my brothers. We have renovated the upper unit and are currently renovating the lower unit. We have removed one wall, and in doing so have made the floor joist in the kitchen span an additional three feet. To help with the springy floor, we added three rows of 2x10 blocking 4 feet apart, and we are planning on putting up plywood on the ceiling fur further stiffen it up.
With that being said, my question is about sound proofing, and more specifically insulation.
We plan on using Sound Isolation Clips like this, http://www.rsic1clips.com/rsic_clips/rsic-2-r.htm, ontop of the plywood and use one layer of 5/8 sheet rock.
So, my questions is that will that system combined with standard fiberglass insulation provide adequate sound isolation, or do I need to spend the extra $50 a roll and buy sound proofing insulation like this, http://shop3.mailordercentral.com/su...ts.asp?dept=24

Thanks for the input.
And if anyone Is interested I am running a blog of our renovation: www.mironovcentral.blogspot.com


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Old 04-29-2010, 11:52 AM   #2
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Insulation with Sound Isolation Clips


Anyone?

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Old 05-03-2010, 11:26 PM   #3
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Insulation with Sound Isolation Clips


How long is that span on those joists? You may need to beef thos up a bit more before you throw up any ceiling.

Sound isolation clips are good, but use 2 layers of 5/8 drywall and Green Glue in between. Also, stuff regular fiberglass insulation up there the full thickness of the cavity.
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Old 05-03-2010, 11:47 PM   #4
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Insulation with Sound Isolation Clips


The span is about 16'.
As stated above, to beef it up we added three roes of full hight blocking (you can see it in the picture)
before we put the ceiling up, we are going nail and glue 1/2" plywood onto the joists. (this was recomended by a strctural engineer)
so, back to the origional question. You feel that regular fiberglass insulation is the way to go?
Putting a second layer of rock with green glue would be more expensive then puttng in expensive accstical insulation. Do you feel this would provide better sound isolation preformance?
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Old 05-04-2010, 03:15 AM   #5
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Insulation with Sound Isolation Clips


You'll get alot more strength if you attach a 2"x4"x16', glued and screwed to the bottom of each joist. I don't know if you need that much though.

Here is a similar conversation on another forum.
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Old 05-04-2010, 10:23 AM   #6
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Insulation with Sound Isolation Clips


Quote:
Originally Posted by xxPaulCPxx View Post
You'll get alot more strength if you attach a 2"x4"x16', glued and screwed to the bottom of each joist. I don't know if you need that much though.

Here is a similar conversation on another forum.
I should clarify this.... I am not worried that the extra 30" of span has compromised the structure at all... However, the floor above has become a little more bouncy... the blocking and plywood are to resolve the "spring" in the floor above.

Thanks for the link, it looks like I shouldn't spend my money on soundproofing insulation, but instead on Green Glue and more Sheetrock.

Thanks,
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Old 05-04-2010, 01:25 PM   #7
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Insulation with Sound Isolation Clips


You can find the data from the NRC online, but standard fiberglass is as good as it gets for sound isolation. Having said that, out of the 4 elements of sound isolaton (decoupling, absorption (insulation), mass and damping), insulation brings the least to the party. I wouldn't go thicker than R19, euther. Data shows that going from R19 to R30 brings little incremental performance increases and simply costs a lot more.

http://www.soundproofingcompany.com/..._construction/

Much better data can be had if you increase the mass of the ceiling and damp it as has been mentioned already.
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Old 05-04-2010, 01:38 PM   #8
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Hey, Ted's here too!

Actually, if you glue and screw another continuous board to the bottom, you are creating a deeper beam that's going to give you alot less bounce. All the blocking does is help transfer the point loads around a little, depth = strength in beams.
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Old 05-04-2010, 02:41 PM   #9
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Insulation with Sound Isolation Clips


Quote:
Originally Posted by xxPaulCPxx View Post
Hey, Ted's here too!

Actually, if you glue and screw another continuous board to the bottom, you are creating a deeper beam that's going to give you alot less bounce. All the blocking does is help transfer the point loads around a little, depth = strength in beams.
So basically your giving this plywood stragety a big ... right?
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Old 05-04-2010, 04:27 PM   #10
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Insulation with Sound Isolation Clips


If you are buying 16' long sheets of plywood and putting them up in the same direction as the joists, then yes! Usually the long stuff is much more expensive though.

A floor joist is a beam. To visualize the load is distributed on the beam, imagine drawing a long oval on the side. In the center of the beam, the forces are parallel to the beam near the top and bottom. This is why you can bore a sizable hole in the dead center of a beam and not loose any structural capacity - most of it's strength is in the inch of wood near the top and bottom. The ends are different of course, here the load is carried in the up/down axis.

By adding that bottom flange, you are essentially turning your 2x10 joists into 2x12 joists, which gives you a tremendous amount of stiffness for your span. Looking at this Span Calculator, the joists you have are a little undersized, assuming they are Douglas Fir.

You could still put normal plywood under that new glued on flange.
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Old 05-06-2010, 04:09 PM   #11
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Insulation with Sound Isolation Clips


Paul, these are very helpful posts. There's a great deal of misunderstanding about joists and support structures in general. Thanks for taking the time to post these points.

I learned something with the addition of a bottom flange increasing the capacity. Curious, does the addition of the bottom flange automatically allow you to move up in beam size in a common span table? For example, if you had a 2x10 and added the bottom flange, can you now "legally" look at this as a 2x12 on the span table?

Is there a protocol for the flange material and attachment method?

Thanks again. Very interesting thread.
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Old 05-06-2010, 04:26 PM   #12
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Insulation with Sound Isolation Clips


That is one of those questions that crosses the line from this is the "normal way to do it" to the other side "you need to have an engineer figure that out". I've never heard of anything laid out in an accessible table. You run into problems like type/thickness/depth/number of fasteners per inch... and that number can change along the span of your built up beam!

The only thing we as mere mortals can do is get as close as we can, then overbuild the heck out of it! Seeing that he's pretty close already, adding another 2x4 flange to the bottom should overbuild it sufficiently.
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Old 05-06-2010, 04:44 PM   #13
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I agree. Thanks for your insights. Very helpful.

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