Weird wall construction; is this a 3 leaf wall system?

I've run into another problem. I am not sure if this is considered a 3 leaf. Current wall in my place exists as 1/2" gypsum. Wall is constructed floor to ceiling 20'. It is on metal studs. Then 3" insulation. The neighboring space has a wall made of 1/2" gyp on same metal stud. Only their wall only goes to 10'. There is a drop ceiling. Above 10' on their wall there is nothing. Since their wall is connected to nothing it doesn't seem to me to be a 3 leaf system since there is 10' where there is no wall. I would like to build my triple gyp wall in addition. I just can't figure out whether or not that is really a 3 leaf wall system. Here is a rough and basic picture

here is a better picture. The high wall is 20', the shorter wall is 10'.

On the current wall construction... It is either as noted as 3" insulation... Or 2"insulation and 1" airgap, which is the more likely scenario

I'm trying to figure out if either 1 of these scenarios should play out: 1) It is not a 3 leaf system. Go ahead an build the inner wall and be done with it. 2) It is a 3 leaf system... Tear out the drywall on my side and build the inner wall. 3) Deal with the 3rd leaf, as there is nothing I can do about it on the other end. The adjacent business can't do construction to mitigate any insolation issues. Their drywall goes to 10' and that's it. And I can not add another layer of drywall to their side. So that leaves me with 2 options of how I build the wall 1) 1/2" gyp--GG--5/8" gyp--GG--1/2" gyp on stud--6" air--4"insulation-5/8" gyp on stud--3" insulation open air pocket--10 of 20' drywall on neighboring side 2) 1/2" gyp--GG--5/8" gyp on stud-6" air--4" insulation--1/2" gyp--5/8" gyp to 10' with open air gap

here is another illustration. My goal STC is 65...just to quantify a number for you Can this type of construction overcome the 3rd leaf and still provide me with close to that STC rating?

I was going to say that it's a 2 leaf system until you added the 1" airspace. So, that 1 gypsym layer + insulation of 2" is a wall just for "decoration" and is not connected to the 2 layer wall with 4" gypsum?

The 10' gypsum on the right is my adjacent neighbors wall. Their wall only goes to 10' with nothing above. They have a drop ceiling. Their wall is on the same stud that my current wall is on. It is the first piece of drywall on the 20' wall. As it stands now, there is 1 layer of drywall-stud-insulation-neighbors drywall. My original wall and their wall share the same stud. I am proposing adding an additional sheet of drywall and green glue, then building my inner wall. I will try to come up with another drawing of how things stand as of now.

Here is what the current wall structure is: The space on the left is my studio 4000sq ft. The space on the right is another company.

vicksburgstudio wrote:

Here is what the current wall structure is: The space on the left is my studio 4000sq ft. The space on the right is another company.

First off - if the party wall doesn't go all the way up to the hard ceiling then everything you're doing is going to be pretty much useless..... UNfortunate that yuou couldn't strip the drywall off your side of the wall and add the extra drywall and green glue to theirs......... Next - your inner wall couples to the hard ceiling above - which will mean that the ceiling will probably end up your weak point (with fklanking). I don't hold out a lot of hope with this approach...... Rod

We are going to put in a drywall ceiling that drops to 16'. I didn't indicate that on my drawing. Rod- Are you saying that it is useless even if I do what I indicated in my first set of drawings? I planned to attach another sheet of drywall and GG to my current wall... Then have 12" airspace then build a wall triple drywall plus GG. My theory was that my current wall and their half wall would act as one mass... Then i add airspace and the inner wall would be my second leaf... Is that not correct? This could be another devastation for me. I appreciate your help Rod. It has been 7 months that I have been trying to find a place... Tons of failed negotiations, tons of code issues, now this... I can't catch a break, and I am wearing thin. Hopefully there is something I can do..

rod gervais wrote:

vicksburgstudio wrote:

Here is what the current wall structure is: The space on the left is my studio 4000sq ft. The space on the right is another company.

First off - if the party wall doesn't go all the way up to the hard ceiling then everything you're doing is going to be pretty much useless..... UNfortunate that yuou couldn't strip the drywall off your side of the wall and add the extra drywall and green glue to theirs......... Rod

I can strip my wall no problem, I just don't know how I could fix the drywall on their side, and it would probably not be feasible to double their drywall. Here is a picture of exactly what I thought would work. Sorry they aren't to scale, but I think you get the picture.