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PostPosted: Thu Feb 12, 2004 9:23 pm 
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but if the goal is to have the insulation touching the drywall... and 2x4's are 3.5 inches, how can you do that if your rockwool is only 3?


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PostPosted: Thu Feb 12, 2004 9:47 pm 
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Aaron, I'm not familiar with "706" - did OC rename 705 to reflect the true density of 6 PCF, or is this something new?

For inside of walls, USG recommends 2-5 to 3 PCF stuff - heavier hurts isolation at low frequencies, and lighter hurts high frequenciy TL.

For acoustic treatments, it depends on the use - for bass traps/direct 90 degree incidence, the heavier stuff appears to do better. For grazing incidence, however (usually the case) the heavier stuff reportedly doesn't do as well because the interstices are too compressed to allow penetration as well.

TB, one way panel contact is achieved is that some manufacturers make their batts a full 24" wide, so that when you stuff it in between studs it has to "bow" out some. This automatically puts part of the insulation in contact with the wall panel. Using these batts, you would put them in so that the bowed out part touches the wallboard panel in the middle of its un-supported area (half way between studs) and NOT so the EDGES of the batt touch the panel.

Some lighter spun fiberglas would probably be compressible so that you could put 6" into a 3-1/2" cavity, but it would likely be too tight. You're better off using the rigid, and bowing it for light contact.

If that isn't an option, you can cut narrow strips (maybe 4" wide) from an R-11 batt and glue them to the 3" Rockwool boards running vertically down the center between studs; that narrow a piece won't make too hard contact, but WILL dampen the panel where it needs to be... Steve


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PostPosted: Fri Feb 13, 2004 11:37 am 
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706 is a 6 PCF board, hence the 703 is a 3 PCF board.

Steve, you brought up a good point on the insulation "bowing", and now I've got a question on that. Steel studs are so thin, that there shouldn't be any bow on the insulation when I install it. Where as with wood, the stud makes the space smaller and it will cause it to bow. I'm wondering if I shouldn't do a 4". Considering the steel studs, and there's no board on the back side, shouldn't be an issue...just cost more. Any thoughts? Especially since ther will be RC on the studs.

Thanks,

Aaron


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PostPosted: Fri Feb 13, 2004 2:53 pm 
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OC 705 is their 6 PCF stuff AFAIK - it doesn't follow their numbering scheme for some reason. If you have info on a "706" product, I'd like to see it.

I'm still not clear on the purpose of that particular wall - are you using it as the front of a bass trap and planning some kind of cloth cover? If so, then thicker is better. If there will be wallboard over, then thicker isn't necessary and the heavier density may hurt your low frequency TL.

One way to achieve a "bow" is to cut thin spacers and "shim out" the stud cavity slightly (about 1" should work) - these could be made from thinner insulation board, or even strips of 2x4 ripped down to fit in the stud channel... Steve


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PostPosted: Fri Feb 13, 2004 3:32 pm 
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I'm still not clear on the purpose of that particular wall - are you using it as the front of a bass trap and planning some kind of cloth cover?


OK, let's see if we can clear this up some...


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PostPosted: Fri Feb 13, 2004 4:40 pm 
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:oops: :oops: :oops: :roll:

OK, got it - if you put the channel behind the insulation as you mentioned earlier, so that the batts won't be pushed out of the stud cavities, then I would just cut some patches of fluffy R-l11 and stick them to the batts between the RC's, so that the panels are damped somewhat... Steve


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PostPosted: Fri Feb 13, 2004 5:18 pm 
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Sounds good. Now I just need a crash course in AC Duct work. It's coming around the corner quick. Subfloor should be going on no later than Saturday. Then it's time to start framing the walls (outer shell so to speak).

I know you posted a picture here on attaching the top rail to the floor joists using wood studs. But I didn't really understand what you explained or drew on the steel stud & track for the isolation sway bracket. Can you draw a diagram on this? May have to use it afterall.

Thanks,

Aaron


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PostPosted: Fri Feb 13, 2004 7:29 pm 
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OK, so you need a method for anti-sway for the top of a steel stud wall under wood joist ceiling frame? What's your existing joist size, centers, and span? Also, if you know it, what is mounted on top of the joists (your upstairs floor construction)?

These measurements will determine the spacing between the top plate of the wall and the existing floor joists... Steve


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PostPosted: Fri Feb 13, 2004 7:58 pm 
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What's your existing joist size, centers, and span? Also, if you know it, what is mounted on top of the joists (your upstairs floor construction)?


Joists are 2x8, for the most part they are 16" OC, and roughly about 11 1/2 feet from wall to steel beam. Depth of room is approx. 16', and the width is 17' on the widest stretch of wall (front wall).

The existing floor above is a sub floor, consisting of several boards run diagonal (house built in '55) and then wood floors on top of that. As far as I can tell.


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PostPosted: Fri Feb 13, 2004 8:29 pm 
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OK, near as I can tell your upstairs floor would have either 50 live, 10 dead load rating or 40/20 - worst case, you would (if you wanted to) be able to hang an additional load of at least 5 pounds per square foot on those joists and still be within design limits. Using L/360, which these calculations assume, you would have a maximum floor deflection of 144/360, or 0.4 inches, halfway between the wall and the steel beam. I would allow 1/2" between a top pad of 1/4" rubber (preferably EPDM) and the existing joist.

One more question (yeah, right, like eating just one Lay's potato chip :=) - Will your "sway-less" wall be running perpendicular, parallel, or an odd angle to the ceiling joists?

(Take your time on this, I probably won't get to the drawing for a day or so)... Steve


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PostPosted: Sat Feb 14, 2004 11:27 am 
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I haven't a clue what you just told me there... I'm not a structural engineer. I had someone else do the calcs on the steel beam I put in.

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One more question (yeah, right, like eating just one Lay's potato chip :=) - Will your "sway-less" wall be running perpendicular, parallel, or an odd angle to the ceiling joists?


All 3...

Thanks,

Aaron


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PostPosted: Sat Feb 14, 2004 2:12 pm 
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Sorry, those #'s refer to loading per square foot for live loads (people walking around, moving pianos, etc) and the second # (smaller one) for dead loads (permanent, such as flooring, ceiling material, NON-moving pianos, etc) - 40/20 means 40 psf live load, 20 psf dead load. These are typically calculated using a spec called L/360, which is simply the span in inches divided by 360. So a 360 inch span would be allowed 1 inch of deflection maximum, where a 180 inch span would be allowed 1/2 inch. For really stiff floors, like where tile will be used for floor covering, the spec is increased to L/480 or even L/600. I would also use these stiffer specs if I were building a studio on an upper floor, mainly to lower the resonance of the floor.

Bottom line is that you would need to leave a maximum of 1/2 inch gap between your ceiling joists and the top of any walls, less than that if the wall isn't in the center of the ceiling joist span because it wouldn't deflect as much.

I'm pretty buried today, but may get time this evening to do a drawing for DIY sway brackets using steel studs - If you don't have much in the way of metal working tools, though, it might be cheaper to just buy them from someone like Kineticsnoise.com ... Steve

(BTW, I'm not a structural engineer either, I just PLAY one on TV :roll: )


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PostPosted: Tue Feb 17, 2004 12:23 pm 
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OK. I've completed the first layer of subfloor over the weekend...challenging! I also finally got all the pictures from last week, and took more yesterday. The final pix prior to the subfloor are still on film...so may be a few days on those. But the others were taken w/ a digi camera...and here they are...


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PostPosted: Tue Feb 17, 2004 12:26 pm 
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And some more...


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And more...


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