Author Topic: Drop Ceiling, RC-1, Clips, Sepreate Joists?  (Read 12249 times)

tom358

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Drop Ceiling, RC-1, Clips, Sepreate Joists?
« on: October 04, 2006, 08:55:24 PM »
I was wondering what is the best way to soundproof the ceiling in my townhouse basement, drop ceiling or seperate ceiling joists.  Also I was wondering if anyone can spot any flaws with me plans.  I am building a HT in a 17' x 11' basement with concrete walls on three sides.  I am planning on staggering the one wall that does not have concrete.  I have figured on doing all the studs 24 in center with rock wool insulation, 5/8 drywall, Still not sure about Green Glue because of cost, and another layer of 5/8 drywall.  The ceiling I plan on putting R-30 9.5 inch thick insullation but not sure what else.  RC-1, drop ceiling, decopled ceiling etc.  I have ont purchased anything yet so any advice would be greatly appreciated.  Thanks

I may be overdoing it or not.  As I posted before I carnked up the sound and went to the neigbors and I could hear it but not to to bad, however I plan on listening more at 9 or 10 at nite!!  I plan on using AR 910a Front Speakers, AR 110 Surrounds (4) and a yet to be determined center and sub powered by, still not sure, but Onkyo txsr803 and an older Harmon Kardon to power the fronts.

johnbergstromslc

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #1 on: October 05, 2006, 12:22:32 AM »
Sounds like you're in good shape in regard to the walls.

The most effective ceiling isolation is separate joists, but that adds a lot of work.  A system I like (and recommend a lot) is SSP clips + drywall furring channels + 2 layers of 5/8" drywall.  I think the STC value for this is about a 64, which is excellent.

See the details at:  http://www.kineticsnoise.com/arch/isomax/index.html
(They're the manufacturer of the clip, which they call 'Isomax'.  SSP merely licenses their product.)

Don't do the drop ceiling - I'm assuming you mean suspended acoustical ceiling.  It won't work.  It's primarily for absorbing the echo in your space, it won't cut down much on the transmitted noise.  

Your choice for insulation is fine.  Cotton works marginally better (as you will see, interested parties will try to shove it down your throat and tell you it's the only thing that works - it isn't) but once you see the price, I think you'll go running back to fiberglass.

Good luck.  Sounds like it's gonna be a quiet space.

tom358

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #2 on: October 05, 2006, 02:18:12 AM »
Thanks for the info.  I do like those clips but isn't it cheaper to      add some new joists I figure 15 for my 17 ft long room.  Home depot has 2x6x12 for $5.63 each (the room is going to be 11 ft and some odd inches.  I am assuming you nail or use metal braces to attach these to the new walls.  Am I way off here or on the right path.

Thanks again

johnbergstromslc

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #3 on: October 05, 2006, 09:13:50 PM »
The clips+drywall furring channel add about $1.00/sq.ft., assuming you're going to do the labor yourself.  The clips are $5.25 each+shipping, each covering 8 sq.ft. (installed at 24" X 48" spacing) and you can get channel at Home Depot/Lowes for $ 2.50 for 10 ft. length.

I guess separate joists would be cheaper, but you'll lose 7+ inches of headroom, vs. 2 inches with the clips.  If you have 9-10 feet to begin with, no big deal.  But if you're starting with only 8 feet, it's something to seriously consider.  I know you can adversely affect the acoustics of a room with a ceiling that's too low.

If you do go with separate joists, yes, you can theoretically install them with just joist hangers.  You just have to make sure to locate the wall studs and drive the nails at an inward angle, so you get some good fastening.  In that case, maybe using screws would be a better idea.  

Another method is to lag bolt 2X6 header boards to each wall at the height you want, then nail the joist hangers to them.  This gives you a bit more flexibility as to where you can locate your joists and a solid surface to seal the drywall corners.  The joints won't move and crack as much as if you left it 'floating'.  

Also, make sure to seal up any electrical box you have in the ceiling.  All those gaps and holes will compromise your soundproofing.  

tom358

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #4 on: October 05, 2006, 10:22:49 PM »
I am missing something here.  Why do I have to lose 7 inches of headroom.  Obviously I have never done this but if I am putting the new joist on top of the new wall why would I lose any headroom except fot the 2 inches I plan on seperating the new joists from the old? Like this:  

http://www.tedwhite.homestead.com/files/floating_joist_close_up.jpg

I hope this works since It looks the best, by the way thanks for the tip on the recessed lighting.  I will build boxes or may go with scounces.

johnbergstromslc

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #5 on: October 05, 2006, 10:42:29 PM »
Yes, I see - his method is a variation on the 'room inside a room' construction.  I've never done it that way and it's a bit of a trade-off, but that should work.  He also has a picture on his site of boxes he built for the lights.  

agtrojan

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #6 on: November 17, 2006, 04:56:04 PM »
Consider using Green Glue to lower the resonant frequency of the ceiling.  Sandwich the Green Glue in between two sheets of drywall.

Take a look at the following link:

http://www.greenglue.org

You can purchase the Green Glue directly on the www.soundproofing.org web site.

Kevin

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #7 on: December 25, 2006, 02:26:58 PM »
Hi John,

Thanks for the informative posts.  I have a similar situation to Tom’s, except that I’m looking for sound proofing from upstairs/downstairs.

A few questions that I have about your recommendations:
1.   I keep reading about caulking cracks and openings.  What constitutes cracks and openings?  Is it just the gaps that I see (flooring to flooring, flooring to walls)?
2.   I have 10” joists; do I have to fill the cavity with R30 or will something like R13 be good enough?
3.   Kinetic (maker of the clip) specifies 48lb loading for 22ga hat channel, is that per clip?  Is it safe to hang two 5/8” sheetrock (kind of close to limit)?  Would it be better to go lower gauge?
4.   Another challenge is that I have original crown moldings on the ceilings.  Should I expect that I basically will have to remove all this, since the finished ceiling will probably be lower than the original?

I think I have identified that the hardwood stairs for the upper unit is the loudest impact area.  For this area, I’m thinking of adding ¼” MLV.
1.   Do I hang the MLV between the joist/insulation and the channel, or do I hang this between the joist/flooring and the insulation?
2.   How do make sure the MLV acts as a “curtain” and not just touches the sheetrock (and lose its effectiveness)?

Since I have the ceilings opened, I’d like to also install canned lights.  I’ve read that I need to wrap this in MLV as well.  Isn’t it kind of dangerous?  What about the heat generated?

How effective is this type of ceiling treatment compared to ripping out the hardwood floors upstairs, applying the flooring treatments, and laying new hardwood down?  I’m not sure if I can justify doing both the ceiling work and the flooring work.

Finally, for labor, I’ve read that I should expect about $3/sqft.  Does that include demolition, debris removal?  If not, what would be the entire labor cost?  I have about 1200 sqft to cover.

Many thanks in advance!

Kevin

johnbergstromslc

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #8 on: December 26, 2006, 09:28:24 PM »
1. You should caulk or seal any gap/edge/penetration.  Basically, anywhere there is a discontinuity in the mass of the wall/ceiling/floor surface.
2. R-30 would be best.  An acoustical lab did a study and found that if you filled a cavity 75% full, you got 90% of the absorbtive effect.  R-13 would probably only add 1-2 points of STC and is not enough.  Also, cotton works no better than fiberglass-keep that in mind as you get the 'hard sell' on this site. 
3. I believe it is 48 lbs/clip.  At a clip every 8 sq.ft., you'd be good up to 192 lbs/32 sq.ft, which is plenty.  They have lots of installation instructions at their website: kineticsnoise.com
4.  Yep.

As for the MLV, I wouldn't bother.  The decoupling from the clips+channel and the insulation are going to kill most of the impact noise.

Yeah, don't wrap recessed lights in MLV.  Not safe.  If you want to use canned lights, spend the extra money and get airtight housing boxes.  They run around 30 bucks and they are safe in contact with insulation.

As you surmised, it would be much more effective to deal with impact noise from above, by adding massive layer 'floating' on top of the existing subfloor, but that would cost as much or more than hanging the ceiling resiliently.   

Can't tell you about labor costs - that depends on your area.  I doubt it includes demo + removal, but demo is the easy part; you could do that yourself.
 

Kevin

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #9 on: December 27, 2006, 08:48:12 AM »
Hi John,

Thanks for the responses.

I'll stick with R30 fiberglass since I, too, can't find any definitive evidence that cotton is better.  At the local HD, R30 fiberglass is already $0.80 per sqft. and I have 1200 to cover.

A couple more questions:
1. If you were to float a new hardwood floor on top, how would you do it without adding more than about 1 inch thickness?
2. When doubling up two 5/8" sheetrock in the ceiling, do I have to stagger the sheetrock, so the bottom layer cover the seams in the upper?  I would think the seams would hold better, but it does seem like a lot more work.

I learned a lot reading your posts, and thanks again for responding to my questions.

Kevin

johnbergstromslc

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #10 on: December 27, 2006, 10:46:46 PM »
I'm not sure you could get good results without adding more than an inch to the floor.  In addition, you'd have to remove and reinstall all the trim and cut the doors bottoms.  You'd be left with an awkward small step at the entryway, too.  It's too much trouble to install an effective floating layer unless it's new construction or a total gut job, where you can adjust doors/trim/stairs to the new floor level.

For the drywall, definitely stagger the seams.  It won't be much more work - your clips and channels will be spaced 24" o.c., so everything will line up.  And before you install the second layer of drywall, caulk, mud and tape the seams & edges of the first layer.  You don't have to do as smooth a job as a finish layer, but if you skip this step, it can hurt performance.


Kevin

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #11 on: December 29, 2006, 03:25:42 AM »
Great, thanks John!!

Kevin_project_done

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #12 on: March 30, 2008, 07:45:55 AM »
Hi John,

I think they dropped my old account due to non-use.  I was the Kevin who asked you the questions end of 2006.  I just wanted to drop you a note of thanks.  I took your advice:

- Airtight cans.
- Isomax plus hat channel.  I went overkill to use 20 gauge steel plus 3-inch self-tapping screws – didn’t want anything falling.
- Two layers of 5/8 sheetrock, offset seams.
- R-30

The challenge that was left was the impact noise from the stairs.  It would have been very expensive to redo the wood just for the stairs.  So I opted to add mass underneath.  I went to a metal shop and they cut some L-beams about 28 inches long and about 10 pounds each.  I screwed them up from underneath the stairs at each step.  Still can hear the impact, but it sounds more muffled as opposed to the loud wood impact noise.

Anyway, I just wanted to drop you a thank you note.  Thanks!

Kevin

joel

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Re: Drop Ceiling, RC-1, Clips, Sepreate Joists?
« Reply #13 on: May 30, 2008, 08:39:30 PM »
A couple more questions:
1. If you were to float a new hardwood floor on top, how would you do it without adding more than about 1 inch thickness?
2. When doubling up two 5/8" sheetrock in the ceiling, do I have to stagger the sheetrock, so the bottom layer cover the seams in the upper?  I would think the seams would hold better, but it does seem like a lot more work.


Kevin
[/quote]
In order to "foat" a new hardwood floor on the top you would need to do a tru-wood adhesive system.  For the underlay use the MLV plus Impact Mat - total of 1/4" thick - and then glue down the hardwood flooring.  You can see this material described at   http://www.soundproofing.org/sales/reduce_floor_noise_with_our_underlayments.htm
With a wood floor/ceiling jois assembly you will get around 70 STC and 55 IIC.  Adhesive is used because any time you nail through soundproofing materials the fasteners become sound/vibration paths into the structure.
Some people use Green Glue between sub flooring and a new T&G sheating - the top layer is the "nailer" for the hardwood flooring.  Since most hardwood flooring materials are 3/4" this would not meet your 1" criteria.

 

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