Author Topic: How about 2nd layer over same sheetrock ceiling  (Read 17455 times)

Clare Nelson

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How about 2nd layer over same sheetrock ceiling
« on: August 25, 2005, 05:08:35 PM »
To reduce sound from an overhead apartment I proposed to a drywall guy to tear down the 1/2" sheetrock ceiling, install sound clips and hat channel, and hang new 5/8" rock. He said he thought it wouldn't be much better (and would be cheaper and less messy) than leaving the old ceiling in place and either 1) fastening a second layer of rock to the joists through it, or 2) fastening resilient channel, again through the old ceiling, and hanging new rock from that.

Assuming I can live with the ceiling lower by 3/4" to 1.5", do you agree? How would the three approaches compare quantitatively? (We aren't trying to stop trains or basses, just household noise).

supersoundproofing

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #1 on: August 26, 2005, 05:34:10 PM »
Many of these "Sound Guys" are still avocates of the 60's-70's technology- that's all they know and don't want to change.

The advantages of new developments are many- the limitations of the old are many.  Best to evaluate for yourself by checking into the differences at http://www.soundproofing.org/infopages/channel.htm
and http://www.soundproofing.org/options_in_sound_isolation.htm

Regarding your specific problem, it depends on whether the noise is airborne (talking, music, etc) or impact (walking, thudding, etc) or both.  Normally more drywall won't help no matter.

BJ Nash
Super Soundproofing CO

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John Rice

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #2 on: September 08, 2005, 06:25:45 AM »
you really shouldn't use that guy who came out, he is way off the mark.

Let me be clear about something, if you put resilient channel on existing drywall and hang another sheet from that, it will actually perform worse than if you didn't use resilient channel at all.

I know that seems odd, but it is caused by something called Mass-Air-Mass resonance that worsens performance if their is an insufficient gap between the drywall and the next surface. In the case where you sandwhich the channel between two sheets of drywall, there is only 1/2 inch of dead space, not nearly enough.

You are much better of tearing the old drywall off, then putting up channel or sound clips, then a layer of drywall, then a viscoelastic material, then another layer of drywall.

The problem is, contractors don't know this stuff.

John Rice

supersoundproofing

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #3 on: October 03, 2005, 10:45:49 PM »
Yes, John is right.  

However, one can remove the drywall panels between the studs quite easily.  Professionals demo men use a special cutter saw that is a disk set to just penetrate through the drywall without cutting through.  It has a vacuume bag which picks up the dust.

The paper that wasn't cut through is cut with a knife, (Carefully so as to not damage wiring, plumbing, etc) and the panels of drywall neatly removed and carried away.  The drywall on the studs can be left or removed as desired.

Now that the space is opened up, the resonance discussed above is not a factor.

BJ Nash
Super Soundproofing Co
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ellmanl

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #4 on: November 04, 2005, 04:25:23 PM »
I also have a ceiling noise issue.

If you have to keep the exsiting ceiling intact, can you still have good impact sound reduction (from above, like walking or floor squeaking) results - maybe by adding a layer of mlv to the existing ceiling, then furring strips, then resilient channels and a layer of gypsym board or sheet rock?  Or is that not going to be worth it wothout removing the drywall already in place? I can hear everything from above...

Also what about those AS clips for ceiling use? Would they hold the channels in place, instead of using furring strips? On your channel page it syas "sound clips, better than resilient channels" but then on the sound clip product page they seem to be working together with the channels...

I guess my problem is that you have so many options here, I can't easily figure out what's best for me!

Thanks.

supersoundproofing

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #5 on: November 04, 2005, 05:01:50 PM »
Because of the resonance problem mentioned above by John, one must either remove the drywall or cut away the panels between the joists to open up the airspace.
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Sound clips are essential for reducing impact noise and while the AS clips are not used for the ceiling at present the other SSP clips are suitable.  All these kinds of clips use "Hat" channel, not resilient channel as a mount for the new drywall panels.

Options are detailed here:http://www.soundproofing.org/treatments_for_sound_control.htm

BJ Nash
Super Soundproofing Co
www.soundproofing.org

Phil

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Re: How about 2nd layer over same sheetrock ceilin
« Reply #6 on: December 02, 2005, 10:13:22 PM »
I have three questions for you.

First, I have a huge problem regarding squeeky floors from the upstairs neighbor.  Will the soundproofing techniques you describe (that is, use of a suspended ceiling with resilient channels or sound clips) block out this noise? Or do suspended ceilings only combat airborne noise and footfall noise?

Second, I had a contractor look at my bedroom ceiling and he proposed the following: without taking down my existing plaster ceiling he will install a suspended drywall ceiling grid with eye lags into exisiting ceiling joists (he made no mention of using sound clips or resilient channels) and then install therma fiber insulation and two layers of 1/2 inch drywall.  Do you think this will be effective? I've not heard of using therma fiber insulation for this purpose, and I'm concerned that eyelags won't be as good as clips or resilient channels.

Third, are any of the techniques you mention possible without taking down the existing plaster ceiling? That would add to the labor costs and, I'm afraid, be quite messy.

Thanks for your help. Hopefully this will work and I can get the first good night's sleep in years.
Phil

 

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