CEILING SOUNDPROOFING

[Nufc23]

Ok experts here’s my situation

The condo I own has a lot of noise transfer to the condo above.
My plan is to:

Rip down existing drywall
Install Roxul Safe n Sound
Install side mounted isolation clips like these
    (https://csrbuilding.ca/product/resilient-sound-isolation-clip-1-%C2%BD-cold-rolled-channel-rsic-1-5crc/)
Install regular hat channel
Install one layer of quiet rock


My question(s) is/are:
1) Is this the best way to achieve maximum quieting of my neighbor?
2) is regular channel (hat) ok being I’m using the whisper clips?
3) can I use regular drywall wall or should it be quiet Rock?
4) If I use regular drywall is double layer with green glue between them the same as one layer of quiet rock?

Any other insight would be appreciated


Ed

[Randy S]

Ed,

If your using clips and channel why do you need the cold roll?
We use these clips and 20 gauge 7/8" hat channel
http://www.soundproofing.org/sales/ssp.htm

Double layer of regular 5/8" drywall with green glue is going to work better then quiet rock 510 or ez snap.

Randy S.

[duleaux]

I have a similar situation but a different strategy.  I live in an apartment in which I am trying to reduce airborne and impact noise from above.  I think I've read every article on the internet about how best to accomplish this goal, and virtually all of the "best solutions" involve tearing down the existing drywall ceiling which for me is not an option.  So here is what I am considering:

1.  Fill the cavities between the existing ceiling rafters by blowing cellulose insulation above the existing drywall ceiling
2.  Apply isolation clips (Whisper, isoTRAX, etc.) to the existing drywall ceiling (please read on, I realize this is considered bad practice)
3.  Apply hat channel to the isolation clips
4.  Apply 1" thick rock wool bats between the hat channel rails.  These bats will fill the space between the existing drywall ceiling and the new layer of drywall
5.  Apply new layer of 5/8" drywall (or QuietRock) to the hat channel rails

I realize that affixing isolation clips to an existing drywall ceiling is considered bad practice because it can create a mass-air-mass resonance chamber between the two layers of drywall that actually can worsen the noise.  However, in step 4, I would sandwich a 1" layer of rock wool (or fiberglass) bats between the two layers of drywall to fill the void and absorb the sound waves traveling between the existing ceiling and new layer of drywall.  So the final structure would have 10" of cellulose insulation between the rafters, the existing drywall ceiling, 1" of rock wool, and a new layer of 5/8" drywall (or QuietRock) affixed to isolation clips.  In the end, I won't achieve full STC reduction, but I assume this would provide some additional isolation of both higher-frequency and lower frequency airborne and impact noise.  Please let me know if you think this strategy has any merit.

[Randy S]

You are right on track when you can not remove the existing drywall.

I would use Isomax clips over any clip.
http://www.supersoundproofingsales.com/SSP-Clips-1/productinfo/09-IS/

Then I would apply 2 layers on the channel, first layer would be cement board 1/2" or greater followed by green glue then 5/8" type X drywall.
Quiet rock is not as heavy and cost way more.

Now the real issue with footfall is the existing subfloor, it is already a drum head and this is why we glue and screw cement board in between the joist in the cavity. when you can not do this you need to cut the perimeter of the existing drywall and fill the gap with acoustic caulking to break it from the walls. when you go forward all rigid layers are to have the perimeter gap and fill with caulking.

Feel free to reach out direct.

Randy S.
760-752-3030

[duleaux]

Thanks Randy!  Great feedback.  Unfortunately, the more I learn about this the more complicated and probably costly it becomes (for example, I did not think about caulking the drywall perimeters.)

[Randy S]

When ever you float on clips and channel or resilient channel you must leave the perimeter free from hard connections and only use non hardening caulk so you do not create a drum effect.
"tight around the perimeter and lose in the middle"

The true cost behind soundproofing is not so much the material as it is the labor costs due to the extreme amount of detail that has to be done in each and every layer.

Randy S.

[guarddog]

you must leave the perimeter free from hard connections and only use non hardening caulk so you do not create a drum effect.

I see this always mentioned, it is also visually covered on this page or your site.

I would assume this means you can't finish the drywall connection point between the ceiling and the wall in the normal way, as it would create a hard connection (and crack the drywall mud I would assume).

So my question is how are you supposed to finish the ceiling drywall edge?  If you leave a small gap of 1/8th or something which you then fill with acoustical caulk you would still have a funny looking ceiling edge.

Is there some type of trim you can butt the ceiling drywall up against to make a straight finished edge?

[Randy S]

The key to this is to make sure you are only using factory edge of the drywall and exact shim sizes.
once the caulking is installed use a caulking corner tool to finish while wet.
coat with a primer and paint, it actually looks good when done right.
if you are going to use molding simply caulk drywall gap first then when installing the molding leave an 1/8" from the molding to the ceiling and attach molding to the wall only and finish the same way with caulking the gap to the ceiling, primer and paint.

I've attached a photo of a corner done with just caulking and primer (before paint) ignore the foam bumper shown, this is for the isolated floor.

Randy S.
760-752-3030

[guarddog]

Yes, that looks good.  Using the factory edge always may not be so ideal, depending on the room.

I was thinking about using a corner bead as well as an option.  Just embedding the side on the ceiling and pushing the other edge up in the gap, then caulk.

I made a little image, attached.

So I could try the factory edge and use the bead if the factory edge does not work out well enough.

[Randy S]

Using the factory edge is my go to because on all my site visits I rarely find guys snapping drywall perfect and it is really visible from sheet to sheet around the perimeter.

I like your idea, how would you hide the corner bead and keep a straight caulking gap the length of the perimeter?

I am really interested in how that looks when finished. This is something we deal with often and is hard to fix without removing sheets of drywall. this could be an instant fix.

[Rick]

@duleaux wrote

1.  Fill the cavities between the existing ceiling rafters by blowing cellulose insulation above the existing drywall ceiling
2.  Apply isolation clips (Whisper, isoTRAX, etc.) to the existing drywall ceiling (please read on, I realize this is considered bad practice)
3.  Apply hat channel to the isolation clips

As a general rule, hat channels are significantly inferior to resilient channels since they are not free to move and achieve dissipation of the sound energy

From http://www.woodworks.org/wp-content/uploads/Acoustics_Solutions_Paper.pdf

I realize that affixing isolation clips to an existing drywall ceiling is considered bad practice because it can create a mass-air-mass resonance chamber between the two layers of drywall that actually can worsen the noise.  However, in step 4, I would sandwich a 1" layer of rock wool (or fiberglass) bats between the two layers of drywall to fill the void and absorb the sound waves traveling between the existing ceiling and new layer of drywall.

What you are describing is called the triple leaf effect (TLE). I've been told by an acoustic engineer a much better way to mitigate or even defeat the TLE is to bore holes in drywall. I'm waiting to get his recommendation on a schedule (size of holes and spacing)

@Randy S I'd be interested in your opinion on the bore-hole solution and recommended schedule.

So my question is how are you supposed to finish the ceiling drywall edge?  If you leave a small gap of 1/8th or something which you then fill with acoustical caulk you would still have a funny looking ceiling edge.

@randy S wrote

The key to this is to make sure you are only using factory edge of the drywall and exact shim sizes.
once the caulking is installed use a caulking corner tool to finish while wet.
coat with a primer and paint, it actually looks good when done right.

Why not tape after caulking? The thin layer of drywall mud + tape + finish drywall mud won't make more of a hard surface than paint. You'll end up with a far better looking angle. That's how I've been finishing angles since 1978 (when we didn't have good acoustic calk). It's possible my approach compromised STC, but I haven't seen any evidence to suggest that.

Even using factory edge/butt against the perimeter, you never get a uniform gap. Construction is never square, the only question is how out of square is it.

The approach I'm taking is two layers of 5/8" rock with green glue between layers.

The ceiling I have planned has a bed room wall covering the ceiling joist. In the bed room and on the other side of the wall the RC channel would need to be cantilevered almost 16" (5" is the max cantilever).  I think I can solve that problem with the AERO-SUPPORT (AS-1) clip http://www.soundproofing.org/infopages/as1.htm

[Rick]

Randy S wrote in http://supersoundproofing.com/forum/index.php/topic,4118.0.html

Mud and tape on the perimeter just created a hard mount around the perimeter..drum head..lose in middle tight around perimeter.

I'm not convinced of that. The ceiling is not a hard mount, it's now floating on the RC channel. The tape on the wall is like anything else attached to the wall.

Tape is flexible, that's why seams/angles are tapped. Fill angles/seams with mud and and it cracks very quickly (because of movement).

You might be right but I'm skeptical taping the ceiling after proper installation (with aprox 1/4" gap on the perimeter with acoustic non-harding calk) will increase sound transmission.  I'll be caulking the perimeter after the first layer of 5/8" rock and caulk again after the 2nd layer.

I'm OK with doing no tape on my ground level if that results in an audible improvement.

[Randy S]

ok lets go through these one by one..

1.  "As a general rule, hat channels are significantly inferior to resilient channels since they are not free to move and achieve dissipation of the sound energy "
 Answer: only if you are not using isolation clips as we suggest. We use isomax clips from Kinetics and they are a rubber clips and allows us to separate them up to 4' apart which is far less contact points that resilient channel does. Also these systems allow us to load far more weight which is key to top noise reductions.
2. Yes, we have been saying this for 20 years..the problem I have run into with contractors and clients alike is space space space...they do not like losing ceiling height and believe me 5/8" does make a difference in the eyes of the client. as for your hole sizes ...as big as you can and as many as you can...
But I like your interest in this topic so I will share a tidbit, if your just addressing airborne sound I have had to design systems with sheer wall in play forcing the triple leaf and have been successful by changing the way the center leaf reacts by dramatically altering its mass and adding dampening to the center leaf.
3. Why not tape after caulking? The thin layer of drywall mud + tape + finish drywall mud won't make more of a hard surface than paint. You'll end up with a far better looking angle. That's how I've been finishing angles since 1978 (when we didn't have good acoustic calk). It's possible my approach compromised STC, but I haven't seen any evidence to suggest that.
Answer. Depending on location acoustic caulk expands and contracts, coupled with floor defection has caused the corners to crack on many of my projects in the beginning. it could be caused from a number of variables from drywall crew, size of gaps, temperature changes to even floor deflection.
after enough times dealing with that complaint I gave up on saying they could. that recommendation will not come from me
4.
The ceiling I have planned has a bed room wall covering the ceiling joist. In the bed room and on the other side of the wall the RC channel would need to be cantilevered almost 16" (5" is the max cantilever).  I think I can solve that problem with the AERO-SUPPORT (AS-1) clip
Answer.  We do not recommend the aero clip for ceilings.. we have done it a couple times..you have to put a screw through the channel into the clip to secure it from coming out of the clip.

Randy S.

[Randy S]

your question.
"I'm not convinced of that. The ceiling is not a hard mount, it's now floating on the RC channel. The tape on the wall is like anything else attached to the wall.

Tape is flexible, that's why seams/angles are tapped. Fill angles/seams with mud and and it cracks very quickly (because of movement).

You might be right but I'm skeptical taping the ceiling after proper installation (with aprox 1/4" gap on the perimeter with acoustic non-harding calk) will increase sound transmission.  I'll be caulking the perimeter after the first layer of 5/8" rock and caulk again after the 2nd layer."

my response.
RC 1 is a float and flexible, you should be able to push up in the middle of that ceiling a tad bit.
RC 2 is not
Clip and channel is not .

I do have one contractor that has been using that yellow fiber tape and caulking for his corners for 20+  and it has worked for him.. but normally contractors new to this do not seem to have the skill to finish it well.

I like your views and interest in this.
we should chat on the phone sometime.

Randy S.
760-752-3030