Author Topic: Best way to soundproof a ceiling  (Read 17786 times)

deb78

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Best way to soundproof a ceiling
« on: July 31, 2008, 04:12:17 PM »
we current rent out the 1st floor, we live on the 2nd floor.  The living rooms are right above each other.  the 1st floor people are moving out, before we get new people in we would like to add more noise protection.  Currently when 1st floor watch their movie with their 5.1ch speakers we can hear it in our living room.  The living room it self is 23' x 26' with 9' ceiling.

We don't have carpets on our floor, just Pergo, under that 3/4" OSB than the floor joists than their 5/8" sheetrock.  We installed R-30 between the floor joists.

So far we came up with 4 different ideas.

1) run some new 2"x4" @ 16"OC under the current 5/8" ceiling and add a new layer of 5/8" sheetrock
2) keep the current ceiling, add green glue and add another layer of 5/8" sheetrock. 
3) same as #1 above, but this time we use a soundproof sheetrock like Quietrock.
4) same as #2 but use a soundproof sheetrock.

We are not sure how to find (guess) the final STC value.  Quietrock claims their 1/2" sheetrock is 49-68 STC. not sure What GreenGlue is rated for.

We are guessing our current STC value is the high 30's maybe the very low 40's. 
Any other suggestions?

joel

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Re: Best way to soundproof a ceiling
« Reply #1 on: July 31, 2008, 07:30:25 PM »
The easiest choice for best results is number 4 (of the options you list).  Use Green Glue at the rate of 2-3 tubes per 4x8 sheet of rock.  You will need between 4-5 cases of Green Glue.  Be sure to leave a 1/4" gap at the perimeter of the ceiling - where new ceiling panels meet walls.  Fill this gap with acoustic caulk and paint.  Finish the field of the new ceiling panels in the standard manner and paint.
Green Glue adds about 10 STC - most importantly it gives a 13-15 dB drop in low frequency sound transmission by damping vibration caused by sound waves.  Make sure there are no openings in the entire ceiling.  If there are any recessed lights or speakers inside the ceiling you can forget about soundproofing the ceiling on the first floor - nothing you add will solve the problem.  And be sure to decouple any speaker mounts at walls/ceiling with padding tape or anti-vibration pads.

deb78

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Re: Best way to soundproof a ceiling
« Reply #2 on: August 01, 2008, 03:33:43 PM »
Joel can you give me a guess STC on option #2?  Because the apt will by emepty and we have to repaint the whole place anyway.  If option #2 gives a better STC than #4 we will do that instead.

would it be safe to say option #4 with the GG will give us a total STC of at least 50 or higher?

badman70

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Re: Best way to soundproof a ceiling
« Reply #3 on: August 02, 2008, 12:45:36 PM »

Isn't the options your proposing going to be limited by the structure noise within the walls?  Assuming the TV and speakers are probably up against a wall, I figured most of the noise would be running up the wall studs which are probably completely connected to the 2nd floor walls.  So a lot of the sound probably is not coming through the floor anyway. 

Isn't this the case John?

deb78

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Re: Best way to soundproof a ceiling
« Reply #4 on: August 03, 2008, 03:18:04 PM »
I don't think there is much we can do to limit the structure noise at this point.  The studs are completely connected to the 2nd floor.  But at this point in time anything is better than what we have now.

joel

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Re: Best way to soundproof a ceiling
« Reply #5 on: August 07, 2008, 06:45:08 PM »
Hi deb,
The STC for option 2 would go like this - adding one layer of 5/8" dry wall adds 4 STC and the Green Glue adds another 10 STC.  green Glue damped dry wall also gives a 13-15 dB drop in low frequency (impact) sound.
Remember, the quiet rock numbers (49-68) is an assembly number that takes into account framing, air space, insulaiton, etc, with quiet rock (usually on both sides).  It does not really say what the material alone ADDS to an existing assembly.
The STC numbers I listed above are what each component adds to existing.  Dry wall claims to have an STC of 28 - again, that is an ASSEMBLY rating, not what it adds by itself to existing.
Hope this helps clear things up for you.

deb78

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Re: Best way to soundproof a ceiling
« Reply #6 on: August 07, 2008, 09:12:14 PM »
Ok I got it.  there is no STC value to quiet rock by it self.  Well I guess using GG with the quietrock should be much better than what we got now.

I noticed on the quietrock also wants me to use their "glue".  I can skip this since I am use GG right?

Mark Daveis

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Re: Best way to soundproof a ceiling
« Reply #7 on: August 08, 2008, 10:15:26 PM »
Adding damped mass to your roof will only yeild about 4 or 5 stc more max.
Qrock already has viscous compound in it so more GG is a waste of money.
You need to float a roof with some airspace for a decent stc of 20 or more extra and adding extra mass to an existing roof only has a slight hardly noticable effect. Dont you understant how mass law works? :)

deb78

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Re: Best way to soundproof a ceiling
« Reply #8 on: August 10, 2008, 12:55:33 PM »
Adding damped mass to your roof will only yeild about 4 or 5 stc more max.
Qrock already has viscous compound in it so more GG is a waste of money.
You need to float a roof with some airspace for a decent stc of 20 or more extra and adding extra mass to an existing roof only has a slight hardly noticable effect. Dont you understant how mass law works? :)

Mark,
so you are saying going with opt #1 adding some air space is much better way than going with opt #2?
Because this is the main reason why I made this post.  I can't seem to find one post that say which way is better.
thanks
Deb

Mark Daveis

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Re: Best way to soundproof a ceiling
« Reply #9 on: August 10, 2008, 11:31:27 PM »
If you double the mass of an existing wall/roof by say adding drywall and gg or mlv and so on you are only going to get at most an increase of about 4 or 5 stc according to mass law. Damped mass such as mlv or using GG conforms closer to mass law so works better but its not possible to beat mass law.

If you want a higher increase of stc then you need an airspace of more than 2 inches and say 2 drywall layers after the airspace and with GG is better to damp it to get an increase of at least 15 stc or higher. Without the air space you wont get much of an improvement. :)

deb78

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Re: Best way to soundproof a ceiling
« Reply #10 on: August 11, 2008, 02:00:13 AM »
If you double the mass of an existing wall/roof by say adding drywall and gg or mlv and so on you are only going to get at most an increase of about 4 or 5 stc according to mass law. Damped mass such as mlv or using GG conforms closer to mass law so works better but its not possible to beat mass law.

If you want a higher increase of stc then you need an airspace of more than 2 inches and say 2 drywall layers after the airspace and with GG is better to damp it to get an increase of at least 15 stc or higher. Without the air space you wont get much of an improvement. :)

Mark,
this is the problem I am having with your suggestion.  I am a newib and that is why I am here hoping to get advice on what to do.
We have no problem adding in an air space, but to add 2 layers of 5/8" thick srocks under what is already a 5/8" layer we are worry about the weight.  As per my post our living room size is 23x26 there is no support in the middle of the room. 

Beside that are you suggestion using 2 layer of 5/8" with GG instead of 1 layer of Quietrock?  (once we add the air space that is)

lastly that we seems to be back at square one.  As you can see from my post we are willing to do the work but we just not sure what will work the best.  That is why I listed 4 different options.  I hate to do the work and spend all this money and get little or no result.

From Joel's post GG plus another layer of srock will give us about 15STC  and here you are telling me that adding another layer with or without GG will give me about 5STC. 







joel

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Re: Best way to soundproof a ceiling
« Reply #11 on: August 11, 2008, 07:07:50 PM »
This is getting unwieldy.  Mark, why don't you let the lady know where to look up "mass law" for herself.  The solution I suggested is based on hundreds of in-the-field installation results - not tables ane "laws" in a textbook.   And isn't the original post about how to solve impact (structure-borne) sound transmission also?  If you create a 1" gap it will turn into a reverberation chamber.  For a real review of this see the field test results at 
http://bkl.ca/sites/bkl/files/resilient_channel_in_floor_assemblies.pdf
In order to counter this reverb in a 1" or so "air gap" you will need to line the entire up-side surface of the material (whatever it may be) with at least 1/4" closed cell vinyl nitrile foam to absorb and block sound in the now created contained space.
Let's keep it simple and solve the ladies problem by answering her original question options. 

Mark Daveis

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Re: Best way to soundproof a ceiling
« Reply #12 on: August 11, 2008, 10:03:22 PM »
If you have already got 30 stc or so then adding a layer of drywall and GG wont increase it by another 15 to 45 and more.
If you could do something like that then you could sell your idea and become very rich but its just not possible even if you used 4 times the mass of the whole roof structure you have.

I said a 2 inch or larger cavity and yes you would line it to stop resonances and drum effect but you can use just a single layer of QR as its heavier than normal drywall and has viscous damping built in. I have built plenty of designs and know what works in the field and usual is 2 sheets of very thick plywood or drywall with GG because you need about 20 kilos of mass per metre squared but still one layer of drywall with an airspace will work much better than fixing it to your existing structure.

Check out these links before deciding.

http://www.soundonsound.com/sos/apr98/articles/soundproofing.html

http://videoexpert.home.att.net/artic2/238austu.htm

I have a very good report with a mass law graph included and if you really want that I can chase up the web link! :)




johnbergstromslc

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Re: Best way to soundproof a ceiling
« Reply #13 on: August 11, 2008, 10:56:35 PM »
Just to chime in, deb, you'll get much better soundproofing if you tear off the current ceiling and hang the new ceiling on isolation clips + hat channel.  It's extra work and counterintuitive to 'go backwards' like that, but the results will be worth it.  Since you've already insulated your joists, you're in good shape there.

A resiliently hung ceiling with 2 layers of 5/8" drywall and insulated cavities (assuming good sealing) will get you an STC in the mid-50's.  Even higher if you use Green Glue between the layers.  Personally, I'd advise you to skip the Quietrock - it's an overhyped and overpriced product, to be sure.

Any of the solutions you proposed in your first post won't get you the kind of isolation you're looking for... 

bjnash

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Re: Best way to soundproof a ceiling
« Reply #14 on: August 18, 2008, 05:13:19 PM »
Just to chime in, deb, you'll get much better soundproofing if you tear off the current ceiling and hang the new ceiling on isolation clips + hat channel.  It's extra work and counterintuitive to 'go backwards' like that, but the results will be worth it.  Since you've already insulated your joists, you're in good shape there.

A resiliently hung ceiling with 2 layers of 5/8" drywall and insulated cavities (assuming good sealing) will get you an STC in the mid-50's.  Even higher if you use Green Glue between the layers.  Personally, I'd advise you to skip the Quietrock - it's an overhyped and overpriced product, to be sure.

Any of the solutions you proposed in your first post won't get you the kind of isolation you're looking for... 

This is true.

BJ