2-leaf or 3-leaf ?

[adamski]

Hi

I'm currently in the process of building a studio. The design is a room within an existing room (drywall), which has an upstairs mezzanine floor (studio is on lower floor) - therefore there is a gap of about 2 feet between the existing wall that holds the door and the inner room, to allow for the stairs. I have also used a ratio of 1.0x1.5x1.6, with actual dimensions: height=2m, width=3.2m length=3m.

Currently I have a floating floor made with 2x4 joists resting on auralex U-boats with 22mm floorboards on top. This sits on an existing concrete floor. I am in the process of constructing the frames for my walls.

Now - I was given the advice that it is better to have drywall (2 layers) only on the inside of the frame, so that the main walls go like this: 2 x drywall - frame + rockwool - air gap - existing wall.

Now I have been given conflicting advice that it would be better (if I can afford it) to also have an outer layer of drywall on the outside of the frame.

2 x drywall - frame + rockwool - drywall - air gap - existing wall.

There will be an outer layer on the front wall anyway, so might it be better to extend this all the way round?

Cost is a major factor, but so is decent isolation. However, I will only be doing production and mixing in this room, not very much recording, so I dont need super-hardcore soundproofing here.

Thanks!

[Mark E DeSade]

You should seriously check this site (http://www.johnlsayers.com/phpBB2/index.php) if you haven't already. There are professional studio designers that hang there and answer any questions that might trouble you. BTW, the 2 leaf system will outperform the 3 leaf fairly significantly; it will likely be less expensive as well.

[RICK FITZPATRICK]

Hello adamski. Your heading should read...3 LEAF OR 4 LEAF. Here is why. The existing wall has a layer of drywall on each side of an air gap. Thats 2 leafs already. If you build an adjacent wall with a layer of drywall on the EITHER face of the new wall, you have effectively added another airgap as well as another leaf. If you add another face of drywall on the opposite side of the frame, you add yet another airgap and leaf. However, let me see if I have this straight.
You are building a room with in a room, yet within the AIRGAP of ONE WALL, there is a stairway, no? I'm sorry, but that is NOT a double wall now. If ANY airgap is open to another space, in reality, you have just created a GIANT FLANKING PATH and the wall of the studio is simply a ONE LEAF wall adjacent to a flanking path. AIRGAPS need to be hermetically SEALED. Look at my drawing.
If I understand you correctly, this should illustrate approximately what you are describing, no? If so, as you can see, in reality, the stairway is a hall within the airgap which allows ALL of the airgap to flank noise to this area.

If I am correct, IF you do NOT build a double wall at the stairs, you will render your floating room work useless. as it is only as good as the weak link. Imagine this. Your floating floor is EXACTLY the same as your walls. The airgap below is connects to the wall airgaps, which are NOT SEALED. Therefore, what you have in reality, is a ONE LEAF box with 6 sides(if you are building a ceiling also). Sorry.
This is typical for "net fact" planning in home studio design. The way it SHOULD be built is a DOUBLE wall at the Stairway with a double door. The outer wall should connect to the existing wall, and the inner wall built on the floating floor. But then you have offset thresholds. These sort of conundrums should be thought out in advance. Look at my next reply.

fitZ
PS, the outside wall at the stairway is labled "one leaf". It should read TWO.

[RICK FITZPATRICK]

Here is what "I" think you should do, although at this stage of the game it may be impossible.
fitZ

[adamski]

Thanks for your advice MUCH appreciated.

My original design does in fact include a drywall against the front wall (between the room and the stairs) which I plan to seal using neoprene strips and silicon/mastic sealant.

I had already begun to think that ripping out the existing drywall from the outer wall would help, but did not realise that extending the front wall to create a proper double wall would also make a bid difference. This is all quite new to me, as I'm sure you realise.

In fact there is just enough room to create a 2nd stud frame between the floor and the stairs (phew!), I think I might do it like that, although my thoughts were that having double doors may not be totally necessary, since I dont need super-tight isolation. (plus trying to keep cost down!)

Thanks again!!

Adam.

[RICK FITZPATRICK]

Hello again. Although your floating floor dimensions have already set you airgap depth, you should read this thread to give you some insight PRIOR to building your walls. This is a SIMILAR situation. This stuff can be very confusing. However, knowlege is the key to doing this stuff. Had you read this before, I highly doubt if you would have built a floating room. This is fairly new information, which in reality, renders older train of thought as a brainfart. A floating floor built with very little LEAF mass, actually can make things worse. If your WALLS and FLOOR are not built with LOW FREQUENCY in mind, then it will effectively be worse than building a room on an existing slab.
fitZ
http://forum.studiotips.com/viewtopic.php?t=1653

[adamski]

Yes you're right... I probably wouldn't have.

I've read in a few other places similar things. I'm now thinking of ripping out the floor, counting my losses, maybe still use the floorboards so I can screw the studs into them, use the 2x4's for the extra wall stud frame, and keeping the u-boats for when I can actually calculate this stuff properly, and can afford to do it properly.

What d'ya think? I'm at a point where its not too late to change course.

Thanks!