Drywall...... One layer or Two layers ????

I have a wall i am trying to soundproof. It is a partition wall between two offices and can not be modified. It is steel stud single layer 1/2" drywall on both sides with no insulation. I am going to build a wall on my side of the existing wall and will use wood 2x4s, insulation and 2 layers of 5/8 drywall on my side only. it will be set 2"or 3" away from the existing wall. Here is my Question.............. would it be worth the cost to add another layer of drywall to the existing wall. and would it even help with the sound control? I know about 3rd. leaf's Thanks, Steve

A third layer would help, but if you add a resiliant channel, that will be even better still.

If you can... Tear off the drywall on your side of the existing wall. Pack it full of insulation, leaving the insulation exposed, leave your couple inches of space, then build the second wall, fill w/ insulation (the framing, not the space), put on RC1, attach the 2 layers of drywall to the RC1.

Would he need RC if the wall frames are separate? Probably a moot point though, as the existing partition wall can't be modified.

Need to know the guage of the existing steel framing. If it's 22 AWG or thinner, probably not. If it's structural framing (20 AWG and heavier), I would say yes. But don't quote me on that. From what I've learned here and remember, you want one wall rigid, and the other a little more flexible (or floating), so each wall absorbs different frequencies. Then again, there are other things to consider...Flanking. And tying into the existing structure, etc. Depends on how high this wall goes, what kind of ceiling treatment, and the other walls and their construction. Are we just beefing up the one wall, or building a room w/in a room? If sound can get around the second wall, it's not going to do much.

That's right, Aaron -- the guage of the steel is definitely a factor. Too heavy and it may as well be wood studs from a decoupling perspective! Steve, are you allowed to add an extra layer of drywall to the existing wall? If so, then you may want to consider Green Glue. It's not cheap, but it may address your need. I'm using it in my project. My experience with it so far is just in terms of application. I can say it's pretty easy to work with. Here's the point in my project thread where I get ready to apply the product. --Keith :mrgreen:

Thank you for all your replies,

Need to know the gauge of the existing steel framing. If it's 22 AWG or thinner, probably not. If it's structural framing (20 AWG and heavier), I would say yes.

I don’t think the existing walls studs are strong enough; they probably used the cheapest stuff they could.

Are we just beefing up the one wall, or building a room w/in a room? If sound can get around the second wall, it's not going to do much.

Room with in a Room... my ceiling is 2 layers of 5/8" drywall. Floor is concrete. My new wall will have 2 layers of 5/8" drywall on one side and will not touch the existing wall. I have sealed up the existing wall with acc. caulk and taped and mudded where it needed it. its as air tight as I can get it. What if ........... I build my new wall 3or 4" away from the existing wall do you think that will help.? Or is 1 or 2" enough? Thank you ,, Steve

The more, the better usually. What type of biz is next door? Is the floor one solid slab of concrete? Are you floating your floors? Do you plan to do drums? And most of all, how much isolation do you require, and the budget?

Next door is storage . slab is one solid, control room floor will be floated, adding another layer of drywall may push me over budget for that wall. (2 layers now) drum booth is floated and on the other side of the building. maybe more air space in between the walls is the best I can do to improve that wall. Thank you All,, Steve

fisher of men wrote:

What if ........... I build my new wall 3or 4" away from the existing wall do you think that will help.? Or is 1 or 2" enough?

That's one of the worst things about three leaf walls -- the middle leaf essentially cuts the air into two separate "airs" so you don't get the benefit of the total possible air gap. 1 or 2" is most likely not enough, especially when low end (bassy stuff) needs to be isolated. 3 to 4" is marginally better. Getting up to 8" is much better. 12" is great. More than 12" is greater but, from my second-hand understanding, there is a diminishing return after 12" -- it does get better, but the benefits are not proportional to the extra air.

I don’t think the existing walls studs are strong enough; they probably used the cheapest stuff they could.

Please understand the reason we're asking about the gauge. We're not asking if it's strong enough to handle another layer. (That is a good question and shouldn't be left unanswered.) The reason we ask is that thinner gauge steel studs are actually better at isolation than heavy gauge ones. The relative flimsiness of the stud help reduce the amount of structure-borne noise transfer to the opposite leaf. Typically builders will use the cheapest studs they can get away with. If they're just partition walls that aren't bearing any weight, then they're probably the thinner gauge variety. However, one shouldn't make any assumptions. Just to confirm, you are saying that you are certain that you do not have the option of adding an extra layer of drywall with Green Glue sandwiched in between (and also attached with screws, by the way)... :?: --Keith :mrgreen:

Yes the studs are the lightweight flimsily type. And i can add a layer if i want to I was a little concerned with the weight of the extra rock but it shouldn’t be a problem. And i have room to build the new wall as far away as i need to. that Green stuff is spendy and this wall is 60' long and 13' tall... ouch! Thanks for the help,, steve

Yeah, you'd have to buy three cases in order to account for that entire wall... :roll: By the way, don't press [Enter] at the end of each line of your posts. Let the text wrap naturally.

If you can afford it, I'd add an extra layer of drywall to your side of the existing wall FIRST, sealing it like you've done so far; then, move in about 12" and build your new frame, place strapping or lath across the inner edges of the studs and fill with insulation, and put two (minimum) more layers of 5/8" drywall on the inside of the new frame. The added mass of a second layer on the old wall, plus the wider air gap and at least two more layers on the inside of the NEW wall, would get you somewhere around STC 67, with TL @ 50 hZ around 35-36 dB; the 3rd leaf effect caused by the other side of the existing partition will lower the bottom end isolation - this is hard to predict, but probably somewhere around 3-4 dB worse around 100 hZ. This means that if you were to play acoustic drums in that room, people on the other side of the wall would start to hear anything above approximately 85 dB SPL on YOUR side of the wall... Steve

If he has the option of also adding a layer to the other side of the existing wall, that would help too -- right?

And don't forget to put insulation in the existing wall if you can.

If he has the option of also adding a layer to the other side of the existing wall, that would help too -- right? I'd use that layer instead on the NEW wall - the more mass you can put ELSEWHERE besides the "extra" leaf, the less effect that third leaf will have... Steve

Thanks guys for all your help,,, steve