Hey everybody, I am just copying this from a thread that I got off topic with, so here is the new thread:

Hi all, I have read these forums for some time but just decided to join now and post some information.

I am doing a condo rennovation that has horrible sound problems from the suite above. No underlayment was installed at the time of build (mid-80's) (CORRECTION: MID-90's...which makes this whole story even more unnacceptable...) and at this point cannot be done.

We have torn down the drywall ceiling and found a very poor job. Improper cuts on 3.5" fibreglass batts (CORRECTION: They were actually R8 2.5" batts...I have never seen that!) a very unusual soundboard-resilient channel-5/8" drywall combination that might as well have not even been there. The worst crushing on RC-1 I have ever seen, not to mention that it shouldn't be screwed down on a soft material.

So we are installing a layer of OSB w/GG to the bottom of the subfloor above to try and reduce a bit of foot traffic noise as we cannot get to its source. We are putting in 2 layers of 3.5" fibreglass, using the Genieclip and 7/8" hat channel with the 24" x 48" clip spacing and 2 layers of 5/8" drywall with GG between. Also using acoustic caulk to seal the perimeter and seams of the first layer of drywall, etc...all those finicky things that are recommended to do.

So I wont be posting lab data or any scientific stuff, but our real-world audible results. Right now you can clearly identify where people are above because the noise is so bad. I am not sure where the current IIC rating of this structure is, but it would be very, very low. We are hoping to get into the 50's or so. This is expensive and time consuming, but nothing else can be done that will be dramatically better, other than some type of underlayment or mlv, etc. to the subfloor above....which is not an option to us.

I look forward to posting the results/information. Some may say, "wow, that is a lot of money" but after spending a hundreds of thousands of dollars on a condo, really, what is another 5 or 10??? It is absolutely nothing in retrospect.

Also if you are having a home built for $400,000, would it really be a big deal if you had to spend $2000 on some type of damping agent between 2 layers of subfloor, or some type of underlayment to reduce foot traffic noise to the basement? I say it is like trying to buy framing nails on ebay for your 2500 sq. foot house...really how much money will you save on your 400k project....NOTHING. Spend the money and get the peace of mind!

I really enjoy reading the posts on this site and appreciate all the comments/feedback and tips I have found over the years. Thanks to all.

-Mike

Consider using drywall under that subfloor. Diagram can be found here: http://www.soundproofingcompany.com/...fing_ceilings/
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Ted

Thanks Ted.

I have read many articles but not that exact one yet. We chose OSB over drywall due to price. We were able to get 3/4" OSB for less $$ than 5/8" drywall, plus the lumber yard agreed to rip it down to width we needed at no extra cost. Couldn't really say no to that. Neat and clean and no cutting on-site... So we have (IMHO) a decent amount of mass being added for a good price. Plus the GG in-between. I have never done this before so am very interested to see how much it helps. Will be doing the GG and OSB this Friday if scheduling permits.

Thanks very much for your input,

So I have completed most of what I set out to do on this project...

Installed strips of OSB w/gg, started installing Genieclips & hat channel.

I can say that the sound clip/furring channel is truly amazing. There is massive amounts of vibration in the floor joists, but if you hang on to the hat channel...you cannot feel anything! Very impressive and worth the $$ in my opinion.

We never got to installing any drywall as we ran into a road block...we had to repair/replace EVERY SINGLE JOIST HANGER!!!!! Any construction guys will laugh at this.... There is a steel I-beam running across the condo unit, with wooden 12" I-joists perpendicular to it...no big deal, pretty common stuff.

Every single joist hanger was installed to low, anywhere from 1/8" to an extreme of 3/4" too low. NO construction adhesive anywhere either. So most of these joists were not supported at the ends at all! After many hours of careful hydraulic jacking, gluing, screwing, joist hanger replacement, etc we eliminated 95% of the squeaks and creaks. Some of the joists were so bad they were starting to split apart @ the hangers. Such poor workmanship and such an obvious mistake.

Not sure if I am more upset with the framing crew or the inspector who let this pass. There is no way in hell you would not notice you were doing this wrong, even if were un-experienced or careless.

At any rate, drywalling will start tomorrow, and we have had a very good improvement in IIC already. After we pulled the existing ceiling down and just installed the GG/osb strips, it was already quieter....with no ceiling at all!

I now realize there are pros and cons to using drywall or osb under a subfloor. The osb was nice to work with, but in a place that has a lot of screws/nails missed or carelessly placed joist spacing, drywall would certainly be easier, just push it in instead of cutting nails off or trimming w/saw. Overall osb was OK, cheaper material but a bit more labour so really no difference in overall $$. I think second time over I'd use drywall, just to save on time, as it is usually more important than $$, especially in commercial work. Thanks Ted for your earlier suggestion.

Of note - I could not believe (maybe I just never paid attention before more like it) the importance of lateral bracing in your floor joists. This floor used the wood I-joists which must be braced laterally at the ends and midspan depending on length/load, etc. This building had none to speak of, and had tons of lateral movement on the joists. After we found the proper specs and braced laterally, there was an immediate reduction in foot traffic noise. I mean immediately after the braces were up, it was quieter. Less boom-boom from people walking with their heels. I won't argue any technicalities on this but first hand I noticed a distinct difference in the way the floor behaved.

More to come...

Mike - Why not start your own thread? Sounds like interesting stuff, but sooo off topic in a thread comparing two dampening agents.
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Michael
Flaming Oak Cinema - Construction is done. Only minor tinkering left.

Ditto the separate thread, It would be interesting to see some pictures of these faulty joist hangers. I'm not sure I understand how they were not supporting the joists. What glue are you talking about?
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My Basement -warning progress is slow - Now featuring: Shed building 2009 - place to save those AV boxes

Sure will do with a new thread, and I'll post pics when I have time. We have just started our 1st layer of drywall.

Yeah the joists not being supported - Its a little hard to visualize it but when I post some pics you'll see what I mean. There was actually an interior wall with a bow in it from how much pressure had been on it from improperly installed joist hangers.

Just think of it like this: Whatever height your joists need to be hanging off a steel I-beam....just install the hangers about 1/2" too low. Thus they don't actually do anything, and the joists will eventually sag and/or split. Essentially just the screws from the above subfloor were holding the joists up...BAD.

Mike you can seal the panels to the joists with a bit of sealant (not GG).

You using R19 fiberglass?

Yes we used 5.5" batts of fibreglass and were able to get them in the 18" width (for 19.2" centers).

Seal the panels? Do you mean the sheets of drywall or the strips of OSB we screwed with GG up to the subfloor...??

And yes, I know not to use GG as a sealant. I have a case of SilenSeal on-site for when we need it.

Thanks,

For sealing I was referring to the OSB panels. The little space between the cut edge of OSB and the joist.

Insulation sounds perfect. Doesn't matter where it's positioned in the cavity.

Ted,

I searched quite a bit earlier about this and came up empty handed - is there any test data/evidence on the effect of sealing the OSB or Drywall panels to the subfloor? I couldn't find any info either way...other than it just "seems" like a good thing to do.

But if this good idea only amounts to 0.5 of an STC or IIC point...I'm not sure I'd do it for the labour involved. Sure the sealant is cheap enough, but generally labour is not if you want someone to be careful about it.

Thanks,

Little subtleties like this have no data. Maybe some day. If you consider this too much to do (for the reasons you stated) then it shouldn't cause you to lose sleep. It's all good.

Yeah if I was doing a single room, I probably would. But sealing the seams in multiple rooms would be a bit much. I got the Green Glue in, which I feel is the important factor.

We have not chose our finished ceiling options yet.

So here is another question: I was planning to truly float the ceiling in a couple of ways:

1) No ceiling drywall edge will touch any walls, seal with SilenSeal.

2) Instead of mud/tape on all the inside ceiling corners, we were going to install a type of Crown moulding that is designed to be nailed to the wall only, no ceiling attachment per say. Then there will be a very small gap between the crown mould and the ceiling, which will be filled with paintable latex caulk, then ceiling sprayed with texture as normal. (span-tec probably)

What do you think of this?

We recommend running the ceiling drywall all the way to the walls. Contact. Then seal. The 1/4" space is difficult to maintain in practical terms. In reality, leaving the gap and filling with sealant won't get you any improvement in a field measured acoustic test. So why bother? NOT having the gap will save time and money.

Also, seal and mud will likely be local code compliant, and it's a good idea. Crown attaching to the wall only won't gain you anything. The thought is that the crown will conduct vibration to the ceiling, but the ceiling and walls are already being equally vibrated if there's airborne noise, and it's a poor and lossy connection anyway. So even with the footfall vibration argument, it's just not an effective conductor. So again, why go through the expense of this with no appreciable benefit? Just attach as normal.

Well if there is not any substantial difference in performance then we will likely just drywall to the wall as normal.

And IIC ratings are the only thing we are concerned about, the STC will be naturally high with the process we are doing.

But yeah if the differences are nearly inaudible/measurable then I will build as normal.

Thanks.

To be clear: mud/tape the ceiling to the walls VS small gap w/sealant will have no measurable difference? I thought we would get noticeably more flanking noise the regular way....but if you say NO I'll take your advice.

No practical benefit to leave the gap with ceiling and wall drywall.

Always good to seal that final drywall layer and then mud & tape. This way if the mud cracks down the road you have the sealant.

Any of this is onlt an issue if you have big gaps. Little gaps / joints are pretty stable, so if you HAD to omit sealant, the world would not end. The only flanking that's possible is if there were significant cracks.

OK thanks Ted.

We drywalled our first layer today as we normally would and sealed with SilenSeal. Already there is a significant improvement from the previous build.

Something I never did find any info on was how to install lighting into the DoubleDrywall-GreenGlue-Soundclip type system. I've seen the back boxes for pot lights or use wall lighting, etc.

But I haven't found what to do with a regular ceiling fixture, as I am forced to use them due to condo regulations. So I came up with something, and I suppose enough talk and I will have to post some pictures to go with this story.

The only feasable option I could come up with for ceiling lights was this:

Installed an extra 2 sound clips
placed a 2x4 across two runs of hat channel
used 1/2" plywood to space out electrical box for 2 layers of drywall
used SilenSeal after first layer around electrical box

Should be plenty strong enough, and as far as maintaining sound-proofness....well I'm not sure what else a guy can do...besides not doing ceiling lights. I looked at the putty pads you can get but honestly after the fixtures are installed I can't see much sound leaking through.

We were more interested in getting rid of the "jingling" lights often associated with bouncy floor joists....and the above method did it wonderfully. If there is some other method please share!!

Thanks,

Bringing this back from the dead because I'm considering a similar situation. My theater room has a standard ceiling installed with a lot of noise transmitting to the second floor. How did your results turn out Mike?

Wow,

I nearly forgot that I started this thread....and never did post any of my pics.

So, how did it work you ask.

Well for sound transmitting to the floor above, it is %100. The neighbours honestly do not know there is someone below them.

We were hoping for a better reduction in noise from foot traffic, but it was still quite good.

But yeah for what you are looking for this set up would be king. I guess it depends how far you want to go with it.

For me, the hat channel clips and GG and double drywall did a miracle for reducing noise going upwards to the floor above. It was OK for noise coming down.

In hindsight, we would have used 2 layers of material under the floor to further reduce footfall noise.

You should also check out how your interior walls are built. I found with my own HT room we got a lot of vibration in the room above, just because I have a custom in-wall subwoofer enclosure. (which I can show you if you'd like) The walls are attached rigidly to the floor joists above, and such transfer vibration very, very easy.

You could research this stuff for weeks and still be somewhat confused (like I was), best you can do is research a bit and put down the $$ and hope for the best.

I have been in the audio & construction business for some years now, but to understand how your beautiful sounding system can turn into noise & vibration takes some careful reading and on-site experimentation.

Phone Brian R. from GG or Ted from Soundproofing Company. They both gave me very good advice and were happy to hear my situation and recommend a couple good scenarios. If you want to learn though, you can exhaustively read both their websites for some good info and tech articles.

Good luck

Glad to hear it worked out for you Mike!

I have actually spoken with Ted a bit in another thread that I started and he's given me some great advice. I'm just glad to hear from someone who has done the exact same thing and gotten great results!

Russell

pm sent to thread starter :)