Drywall layers

Can I expect a significant improvement in the reduction of sound transmission from outside sounds (traffic, jets) by adding 2 additional layers of drywall to my existing 2X4 (16 on center) walls inside a cinder block garage. What about green glue (I think it's called) and or using resilient channels between layers of drywall The garage door is being framed in and I'm adding a pair of doors at the entrance (all properly built to reduce noise from leaking in or out Thanks in advance

You will get more responses if you read the only post in the first section at the very top of the forum: http://johnlsayers.com/phpBB2/viewtopic.php?f=17&t=7572 Assuming your walls are built solidly, the main source of noise in and out are the doors. After that, the roof. Adding layers to the walls will increase their TL, but not what you getting right now. The doors should as massive as the walls, before considering adding to the walls. Andre

I forgot to mention that we would be adding two more layers to the ceiling which like the walls is 2x4 framing and R12 pink insulation) re the doors - we will be building 2" thick doors and mounting them according to plans we have from a friend's studio build re: the garage door - it will be replaced by a 2x6 wall filled with RXL40 and drywalled. Then that whole garage door end wall will have an additional wall of 2x4 construction with RXL 40 insulation and a double layer of drywall. Short of building a room within a room (which is still on the table) would an additional two layers of drywall inside the garage be make a significant difference? edit - we're looking at the ceiling right now as our single biggest transmission point

definitely benefit from layers and green glue. if ceiling is week link put GG between each additional layer. if you can afford. It's not cheap but I think it's worth it by hearing from reputable studio builders and not just from forum followers. I spent $1000 extra to do every wall/ceiling/floor, plus, (double) on weak link, in my case ceiling. if just add GG and extra layers GUARANTEED improvement. now, is that to say it's sufficient, WHO KNOW'S?? it's alot of money to gamble. $1000... if you are close already, it may be enough. but more than likely you need to decouple/air space/ect..ect..ect

"additional layers of drywall to my existing 2X4 (16 on center) walls inside a cinder block garage." Unless you can get a cinder block ceiling then anything you do to the walls is wasted effort, it is (the ceiling) the weakest link as Andre has already mentioned. Also , adding anything that makes an air gap in-between layers, like RC would, will make an acoustical hole at low frequency, and this doesn't help either. You be careful who you listen to and who you do not as was mentioned by a forum follower.

I forgot to mention that we would be adding two more layers to the ceiling which like the walls is 2x4 framing and R12 pink insulation)

Whoa!!!! You already have a ceiling up there with 2x4 framing and drywall, and you are going to add ANOTHER TWO layers of 5/8 drywall??? on 2x4's???? Are you SURE you want to do that without consulting a structural engineer? That's an awful lot of weight to be hanging from thin 2x4's (many hundreds of pounds), and right over your head, too! I wouldn't do that, if that were my room...

re the doors - we will be building 2" thick doors and mounting them according to plans we have from a friend's studio build

What does "2 inches thick" mean? Is that 2" foam core, solid core, something else? Like André said: Before worrying about adding layers of sheetrock to walls, you probably should take a CAREFUL look at dealing with doors and windows. If you want good isolation, you need to build something like Rod's "superdoor", which is an awful lot thicker than 2"!!! It's not just the door, either: The seals around the door are extremely important. All three sets of them, on each door.

re: the garage door - it will be replaced by a 2x6 wall filled with RXL40 and drywalled. Then that whole garage door end wall will have an additional wall of 2x4 construction with RXL 40 insulation and a double layer of drywall.

That sounds like you might be building a three-leaf of four-leaf wall. Hard to tell form the abbreviated description with no diagram. But if so, that would be a bad idea.

Short of building a room within a room (which is still on the table) would an additional two layers of drywall inside the garage be make a significant difference?

Make a significant difference to WHAT? You didn't say what you have already in enough detail to figure anything out, and yo didn't mention how loud you are, how quite you want to be, what you are trying to achieve, or even what kind of room it is! You didn't specify anything at all about the construction...

edit - we're looking at the ceiling right now as our single biggest transmission point

Since you didn't mention anything about how you are planning to build that ceiling, it's hard to say.

or using resilient channels between layers of drywall

:shock: That would be a really bad idea. It will most likely trash your isolation. Multiple leaves with tiny air gaps! Ouch.

Thanks for the info guys...lots to ponder hehehe

"like Rod's "superdoor", which is an awful lot thicker than 2"!" 25% thicker :)