Studio design by room expansion in Sao paulo

[volpi]

Hello community,

OVERVIEW
This is my studio design (picture 1), I don't have spare rooms with decent acoustics and isolation so I will have to expand a room by breaking and building walls, at my design green means walls which are going to be build and pink means walls which are going to break. As a rap beat maker and edm producer, I am mostly concerned about the control room since I don't record instruments very often, however, I plan to record vocals and guitar more often, and I would appreciate tips on how to do this right in a one room studio.

Control Room ISOLATION
The control room is already mostly isolated since it is surrounded by a bathroom, the garage and the basement, therefore, I am not that concerned with acoustic isolation here. However, there are some weak links.

Control Room WALLS
The existing black walls are masonry 20cm thick cement walls, but the green wall which is going to be built is going to be drywall because it cannot exceed the thickness of 10cm. This drywall is standard, composed by 2 gypsum plates filled with rock wool(or fiberglass, which is better) layer between them. This is the most exposed wall to outside noise, so tips to improve its isolation are welcomed.

C.R. DIMENSIONS
The control room has good dimensions, a ratio inside the bolt area, the room has its issues, though.
4.50m x 3.40m x 2.45m (14.8ft x 11.2ft x 8.1ft)

CONTROL ROOM ISSUES:
1 There is this triangle shaped corner at the bottom right of the room and I have to close it to maintain the room's symmetry, but I am not sure how to do it, I am either using it as storage space/vocal booth by closing it with a removable panel/screen, or I am permanently closing it with a drywall. What would you do? (picture 2)

2 The wall at the bottom right has holes and it is exposed to noise so I need to seal it. (picture 3)

3 Another problem is the stud inside the studio, is that a big problem? If that turns out to be a huge problem I could expand the room in a different way (picture 4), as you can see this second design also has studs inside the studio, but these studs are closer to the wall and they are more symmetrical. Should I expand the room in this different way to avoid the stud inside the studio? Another solution is building the studio in another part of my house.


SECOND ROOM
I might add a second room to the design (picture 5) since I plan to record guitar and vocals more often, adding a second room would be relatively cheap in this design and it would improve the control room's sound isolation. Having 2 rooms isolates the recording from the monitors and computer noise, besides, I think the 2 rooms setup looks more professional.

The issue here is this second room is small and it is more exposed to outside noise. I've heard that the whole point of a vocal booth is isolation from other instruments, on the other hand, I know vocal booths' dimension ratio don't have to be inside the bolt area, so my question is: is this second room going to be useful for me? Could I record guitar there? Am I wasting money? I am concerned because I've heard about people recording vocals and guitar in the control room.
Second room/guitar room/vocal booth: 3.00m x 2.68m x 2.47m (9.8ft x 8.8ft x 8.1ft)

OTHER LOCATION OPTIONS
If those problems I described turn out to be serious I might move my design to another part of my house, those designs create a room by using existing walls and building drywall walls around it, this is my second option because the isolation would be weaker, I have noise issues there, I would have less privacy and the room dimension are worse. On the other hand, it would be significantly cheaper, to the point that I could use more fancy isolation techniques.
Dimensions: other location 1: 4.40m x 3.30m x 2.49m(this design enable splayed walls, like a subtle trapeze)
other location 2: 4.15m x 3.22m x 2.43m

PRICE AND CONSTRUCTION DAYS
Design from picture 1: R$7700 (U$2600) 9 to 10 days
Design from picture 4: R$9800 (U$3300) 16 to 17 days
Design from picture 5: R$11000 (U$3700) 11 to 12 days
Other location option 1: R$6300 (U$2200) 6 to 7 days
Other location option 2(worst dimensions): R$4000(U$1400) 2 to 3 days
For americans and australians those values must sound cheap, but that is because Brazil is an emerging country with a weak currency, so those values are a lot for brazilians.

OVERVIEW
This post's main goal is to answer the following questions:
A Should I have a second room? If not, how should I record vocals and guitar in the control room?
B How to solve or mitigate those control room issues?
C Should I consider the option of building the studio at other location? Are the issues presented here that bad?
D What is the most sound proof- efficient way to build that wall using a 9.5cm thick drywall?


Thank you for your attention,
Gustavo

[volpi]

Here are the pictures