Question abt shape of control room

[the kid]

Hello,

I am finishing out a cement basement and the area I have allocated for the control room is 11ft x 13ft -- ceilings are abt 8ft. I have heard/read differing opinions on:
(a) leaving the room rectangular and
(b) building angled walls -- so I suppose the front wall would drop to abt 8ft or so.

Aside from the obvious change to the total size of the room, is one shape going to offer me advantage over the other? If it's all the same, a rectangle will be alot easier for the build.

Thanks.

[Glenn Kuras]

Angled walls are good to help with the early reflection points, BUT in a small space like yours you will end up eating up a lot of space which you DO NOT WANT. Keep the room rectangular and treat it well. That will save you time, money and yield you a much nicer room in the end.

[the kid]

Thanks Glenn. I know there are a million threads on wall construction and think I've managed to get thru 600k, but figured to check your opinion.

The builder has recommended two layers 5/8" drywall with MLV in between -- attached to a resilient channel which attaches to the studs.

Does this sound like the best method? Have I missed anything?

[Ethan Winer]

Originally Posted by the kid

The builder has recommended two layers 5/8" drywall with MLV in between -- attached to a resilient channel which attaches to the studs.

MLV between two layers of sheet rock will not do anything except drain your wallet. Resilient channel is good though, and so is Green Glue.

--Ethan

[the kid]

Thanks Ethan.

I've heard of Green Glue but have never used it. If I understand correctly, I should use green glue to adhere the two 5/8" sheets of drywall? And that sandwich is attached directly to the RC, yah?

[bpape]

It's easier if you do the 1st layer to the RC, then add the GG to the back side of the 2nd sheet and put it up.

Just be very very careful with RC. It's extremely easy to short out and mess things up.

Bryan

[the kid]

Thanks Bryan. I'm not sure I understand what you mean by "short out". In doing your method of putting the 1st layer up agst the RC, would you tape at all before using GG and the 2nd layer? Would you stagger the edges?

Thanks.

[bpape]

Tape and just a quick fire coat on the mud on the first layer. Just make sure it's all at drywall level or below in the joints.

Definitely stagger and caulk the seams. Do the ceiling, then 4 walls in order. Then go back and do the ceiling, and the 4 walls in the same order. This makes sure that the 90 degree corners are a Z shape and not a straight passage for sound.

Also make sure the joints along the way don't line up on top of each other.

With the RC, if you mess up and use a screw where there's a stud, the RC is so thin that you'll screw right to the stud and recouple the drywall to the studs which is what you're trying to avoid. This is why I prefer RSIC-1 and hat channel but you don't have a lot of room to lose 4" or so.

Bryan

[the kid]

Awesome - thanks.

I have been led to believe dying/painting my concrete floors will provide a comparable environment as wood floors --- so if I keep concrete, what is the preferred method to terminate the wall at the floor lvel. Would regular baseboard molding touching the wall and floor be okay?

[jwl]

Yeah, that'd be fine. If you're building on slab, presumably the studs are attached to the slab. A piece of trim won't hurt anything.

Also, just to be clear, Green Glue isn't an adhesive. But you do want to apply it between layers to improve soundproofing.

Resilient channel systems might be useful for you, but I'd need to see more about the existing construction. Using channel and/or RSIC clips will decouple the sheetrock from the framing, which can be useful. But make sure you end up with a 2-leaf system, not a 3 or more leaf.

[the kid]

Thanks jwl,

Originally Posted by jwl

Also, just to be clear, Green Glue isn't an adhesive. But you do want to apply it between layers to improve soundproofing.

Thanks for that ... I thought it was an adhesive too. So if using between two sheets of drywall, do I still drill thru both sheets of drywall to keep them in place?

Originally Posted by jwl

Resilient channel systems might be useful for you, but I'd need to see more about the existing construction. Using channel and/or RSIC clips will decouple the sheetrock from the framing, which can be useful. But make sure you end up with a 2-leaf system, not a 3 or more leaf.

I am building right on slab ... and there is basically no existing structure ... everything is open with exception of the future space's back wall which is a finished (insulated & sheetrocked) wall -- for reasons that would this a long-winded thought, I am building a new frame/wall in front of this existing wall. The other three sides to the room do not yet exist.

You've definitely just hit on my lack of knowledge in this area ... I am not sure what a 2 or 3-leaf system is ...


Your help is appreciated.

[jwl]

Yes, you still want to screw both sheets of drywall to the studs, with the green glue applied between.

This graphic illustrates 2-leaf vs. 3-leaf:



Note how the STC40 and the STC63 walls use the exact same materials, just installed differently, which gives 23dB more isolation.

2-leaf systems have Mass - Airspace - Mass (MAM). the STC40 is a 4-leaf system, there is mass (one layer of drywall), airspace (between studs), mass (another layer of drywall), airspace between walls, mass (layer of drywall on other frame), air (between studs on 2nd wall), and mass (another layer of drywall).

The STC63 is a 2-leaf system, mass (both layers of sheetrock), airspace (space between studs and between frames), and mass (2 layers of sheetrock on other framed wall).

I'm a big fan of John Sayers' inside-out wall design, where the sheetrock is on the outside and the studs are inside the room. This allows you to easily l install acoustic treatment build-in to the walls.

[the kid]

thanks jwl --

I think I understand. How much do I "give away" if I follow STC63 but only use one layer of sheetrock on the outside as opposed to two?

[jwl]

Well, that'd be equivalent to the STC57, right? If so, you give up 6dB.