[Danberg]

In building a audio / home theatre room I read some time back of the advantages of doubling up the thickness of drywall.  I am considering building such a room in my basement.  The side walls will be against the block walls, however the ceiling of the room will be up against the bottom of the 1st floor, floor joists. 

To minimize sound traveling up into the 1st floor I recall the mention of a specific product that could be used between the two sheets of drywall.  I am not sure if was an adhesive or simply a sound deadening material. 

Any suggestions to cut down sound transmission to the upper floor? 

[Big Red Machine]

http://www.greengluecompany.com/

But before you rush off to buy that, you need to consider that the doubled drywall is a now a heavy mass, and you want that, but it should also be isolated form the house structure, both the floor joists above and the concrete walls around.

Hat channel and rubber isolators attached to the exisiting structure before application of the drywall will accomplish this.

I used these to great effect:

http://www.kineticsnoise.com/arch/isomax/index.aspx

[MaxCast]

I did something very similar to Big Red's suggestion.

I have two bedrooms above my basement and I "floated" the walls and ceiling and double dry wall and green glue.  I can comfortably listen to music and my kids sleep peacefully. 

Will it stop bomb blasts at reference levels?  No, but they're quieter. 

[BobM]

Don't forget to put insulation in that ceiling and maybe in the side walls too. It not only blocks sound but also helps to absorb some of that extra bass that you need to trap. Even if you don't want to do the whole ceiling (and side walls) you should seriously consider doing this at the "dead end" of the room, where the speakers are located.

[ctviggen]

You might want to hang out here for a while:

http://www.avsforum.com/avs-vb/forumdisplay.php?f=19

Basically, you need mass and decoupling for low bass, and insulation helps, too.  Be advised that this stuff is incredibly expensive.  Clips such as the one discussed above are $4-5/each, and you need a lot of them.  Green Glue is obscenely expensive. 

In your case, the walls against the block walls will be decoupled, although you might consider "floating" them.  For the ceiling, if you can do staggered stud/joist construction, that'll be a heck of a lot cheaper than using those clips.  Also, if you're going to add recessed lighting, they recommend putting each light in its own sound box.

In my case, I'm doing a lot of this for a preexisting room.  If I had it to do over, I wouldn't have done it.  It's very time consuming and very expensive for a house I plan on living in maybe two more years.  That's another consideration -- do you want to invest in your current house?

[arthurs]

Green Glue is obscenely expensive. 

GG is outrageous, I just added a second layer of drywall during a remodel of my listening room and couldn't bring my self to spend what it would have cost to use GG, used contractors glue and it seemed to come out just fine...

[TRADERXFAN]

You should check out Geddes Home theater book on gedlee.com

It gives isolation and absorption techniques with other materials.   Using non hardening glue like liquid nails is recommended for double drywall.
And other unique approaches to floating walls, ceiling, treating HVAC, etc.

-Tony

[JLM]

I used (all to very good effect) insulated/lined flexible ductwork, staggered stud walls, and insulated fiberglass exterior door.

The builder refused to "float" the drywall ceiling and six recessed light fixtures (rated air tight and to be in contact with insulation) were also installed.  Even with blown insulation in the ceiling space, sound travels easily up and down.

Double layer drywall will stiffen the walls which is good, but will do little to reduce sound transmission (unless you use some sort of non-hardening adhesive in between).

[ctviggen]

I used (all to very good effect) insulated/lined flexible ductwork, staggered stud walls, and insulated fiberglass exterior door.

The builder refused to "float" the drywall ceiling and six recessed light fixtures (rated air tight and to be in contact with insulation) were also installed.  Even with blown insulation in the ceiling space, sound travels easily up and down.

Double layer drywall will stiffen the walls which is good, but will do little to reduce sound transmission (unless you use some sort of non-hardening adhesive in between).

Yeah, you need decoupling or else the sound goes through the drywall, through the stud/joist, through the other layer of drywall (or subfloor), and into the room.  Decoupling "breaks" this connection. 

[Carl V]

Aileens' Tacky glue can be used in place of green glue....it's similar.
Aleene's Tacky Glue

https://www.ilovetocreate.com/shop/...inal-tacky-glue

Liquid nails is another option.

as ctviggen stated this process is both effective & expensive.

Previous home had staggered studs & separtated plates/headers.
Clips & dbl thickness 'green wall'.  It worked but it cost an arm &
a leg.  The contractor & sub charged dearly for this.  I don't know
if I'd do this again.

[cujobob]

I had insulation installed in the walls and ceiling in my theater room and it allows me to crank it as loud as I want without disturbing anyone upstairs...except for sound leakage from the doorway (I need to upgrade the door sometime).

[bpape]

Green Glue is obscenely expensive. 

GG is outrageous, I just added a second layer of drywall during a remodel of my listening room and couldn't bring my self to spend what it would have cost to use GG, used contractors glue and it seemed to come out just fine...

Just remember that Green Glue really isn't 'glue' per se.  It's a viscoelastic damping layer which provides excellent isolation down deeper than any of the competitors.  There are others which are similar but none have the performance of Green Glue. 

When you use real 'glue' you essentially make 1 large massive layer that acts as 1 piece rather than a combination of both masses and 2 single masses moving slightly out of sync, thereby introducing some additional damping.

For general room construction to save a few bucks, you can use PAC DC-04 isolation clips to tie the walls to the joist above instead of a hard connection.  This reduces the need for the Kinetics clips, whisper clips, or RSIC-1 clips to be just on the ceiling as the walls are no longer hard tied to the structure.


Bryan

[ctviggen]

I've seen a lot of the data and agree that Green Glue is currently the best out there.  I did a quick calculation of the room I'm trying to cover with GG, and it's about 1033.5 square feet of drywall.  (A room that's about 23' 8" by 17' 6".)  That's a cost of about $890 for GG at $165/case and 2 tubes per 4x8 sheet of drywall (192 square feet per 12 tubes). 

My point is just that taking steps to reduce sound transmission from a room gets very expensive very quickly.  We're up to about $900 and we haven't discussed Silenseal, the two layers of drywall (and someone to finish them), the clips, insulation, boxes for the recessed lights, heavy doors, etc. 

I guess I'm trying to tell the original poster to not do what I did, which was to take down the drywall on the ceiling and one wall (and now all the walls), THEN calculate the total cost to finish the room.  Instead, FIRST, calculate an approximate cost to finish the room, THEN decide whether it's worth it.  In my case, I should've just put in hardwood floors in the rest of the house.  The house would be easier to sell and nicer looking.  Now, I can't afford hardwood floors because the family/home theater room is a money pit. 

Granted, I'll truly enjoy the money pit once it's finished, but I doubt anyone buying the house will begin to be able to contemplate the work that went into that room.  To them, it'll just be a nicely finished room.

[rajacat]

Instead of using Green Glue why not use ordinary adhesive silicon caulk? Who knows Green Glue might just be ordinary adhesive caulk colored green but with a price surcharge. Is there a secret ingredient or what? Seems to me the point of the adhesive is to provide a flexible elastic layer so just about any sticky rubbery layer would do the job. I've found that many products are just relabeled and marketed for a premium. A case in point are the neoprene/cork footers marketed by Mapleshade and found on Audiogon by other sellers. The same footers are sold by soundproofing.com and others at way (multiples!) lower prices.

-Roy

[Big Red Machine]

Nothing on the planet like GG.  It's very "snotty"!!

And you don't need to use 2 tubes per sheet.  I used more like 1/2 a tube per sheet and it worked great.  There's very little difference between 100% coverage and 50% coverage in the past studies, IIRC.  One case for that room would be sufficient.

Also makes nice amp stands if used between 2 pieces of heavy lumber.

[ctviggen]

I'm not sure I could use 1/2 tube per sheet.  That doesn't seem like much, especially when they recommend 3 tubes per sheet.  Also, this page doesn't really have a comparison of 1/2 tube versus 2 tubes per sheet, because the walls are different:

http://www.soundproofingcompany.com/library/green_glue_testing/

In my case, I can only treat one wall.  The staggered stud + GG + 2 tubes/sheet is an STC of 62, which is very high.  It's even higher than the resilient channel version. 

If I could treat both sides of the walls and ceilings, I'd go with less.  As it is, I'll go with 2 tubes/sheet.  Also, the GG is merely an example of one item that's going to cost money.  And unless you have someone do this, it costs a tremendous amount of time (and tools) to do it yourself. 

[bpape]

Instead of using Green Glue why not use ordinary adhesive silicon caulk? Who knows Green Glue might just be ordinary adhesive caulk colored green but with a price surcharge. Is there a secret ingredient or what? Seems to me the point of the adhesive is to provide a flexible elastic layer so just about any sticky rubbery layer would do the job. I've found that many products are just relabeled and marketed for a premium. A case in point are the neoprene/cork footers marketed by Mapleshade and found on Audiogon by other sellers. The same footers are sold by soundproofing.com and others at way (multiples!) lower prices.

-Roy

Sure you can do that - but it's not going to perform anywhere near like Green Glue.  As Ted once said, peanut butter between sheets will do something, we just don't know what!

If you have to cut back 1 tube per sheet still helps.  The thing is that this is something that you can't go back and redo later.  Get this right and save money on things you can add later without major desctruction. 

You're right that proper isolation isn't cheap - and we're just doing the basics here.  We haven't discussed boxing all of the outlets, floating a floor, separate or isolation of the HVAC system, etc.  If anybody ever comes out with an inexpensive way to do isolation, they'll make a fortune.

Bryan

[rajacat]

$7/tube for green caulk. I wonder what it is that makes this any better than ordinary butyl rubber caulk? Have you done listening tests? Hmmm.... oh well, never mind, just another audiophile product.

-Roy

[TRADERXFAN]

Instead of using Green Glue why not use ordinary adhesive silicon caulk? Who knows Green Glue might just be ordinary adhesive caulk colored green but with a price surcharge. Is there a secret ingredient or what? Seems to me the point of the adhesive is to provide a flexible elastic layer so just about any sticky rubbery layer would do the job. I've found that many products are just relabeled and marketed for a premium. A case in point are the neoprene/cork footers marketed by Mapleshade and found on Audiogon by other sellers. The same footers are sold by soundproofing.com and others at way (multiples!) lower prices.

-Roy

Sure you can do that - but it's not going to perform anywhere near like Green Glue. 

Bryan

Bryan,

Is it based on your experience or do you know of anyone that has directly compared Green glue to other glues?  Or some measurements of the viscosity or other significant attributes of Green glue in order to base a comparison?  Why are you sure its so much better?

Thanks for the insights...

-Tony

[mgalusha]

It's not an audiophile product and is nothing like any caulk I've ever used. It never really dries, it strays sticky and nasty and I do mean nasty. It damps the ringing of the drywall. It is expensive, I spent nearly $1200 on the stuff for my room but it is really quiet and well isolated. I have zero regrets about the cost of isolating my room. While not perfect it's good enough that I can have folks over and listen to music and my wife can sleep in the room above while we are partying.

Between the floor, RSIC-01 clips, hat channel, green glue, double drywall, a lot of insulation and a well sealed exterior door I spent about $5K but I'm delighted with the results. Vastly more improvement than spending the same 5K on any component.

$7/tube for green caulk. I wonder what it is that makes this any better than ordinary butyl rubber caulk? Have you done listening tests? Hmmm.... oh well, never mind, just another audiophile product.