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Have you made inside-out walls before?

 
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losthighway
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PostPosted: Sun Nov 30, 2014 3:24 pm    Post subject: Have you made inside-out walls before? Reply with quote

Hi there. I'm in the permitting phase of a build I'm doing in my yard separate from my house. I'm hoping to get the foundation happening pretty soon.

Most of my design is locked in with the exception of some inside out walls with fabric vs. typical walls with absorption added later. This is more for the control room and iso room, than the live room.

My question is this:

When you're adding a second wall, or a new ceiling (room within a room) how do you solve the problems of attaching drywall on the outer part of your wall frame, just from a carpentry standpoint?

I'm especially vexed thinking about the walls nearest to the outside wall, or the tight space between the outer structural ceiling, and the new ceiling inside. You can't just walk around with a drill in a cavity a foot wide between walls and start throwing the sheetrock up on the studs.

My contractor/framer says we can maybe attach drywall to pre-assembled chunks of framing on the floor and then put it up. But I'm imagining the outside corners where the ceiling and walls meet. That all needs to be sealed if it's going to be effective.

Do you know what I mean?

How do people do this?
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Snarl 12/8
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PostPosted: Sun Nov 30, 2014 5:53 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

I'm not sure what you're trying to do, but it sounds like you're trying to build a 3 (or possibly 4) leaf system. The room within a room isn't 2 completely built buildings with both interior and exterior cladding on each. You want the outside of your house, studs, a gap, studs and then the interior drywall. Putting additional layers in actually reduces the soundproofing. Counter intuitive, but true. Have you read the Rod Gervais "Build it like the pros." Has your builder?
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Snarl 12/8
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PostPosted: Sun Nov 30, 2014 6:18 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote


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floid
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PostPosted: Sun Nov 30, 2014 6:21 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

sounds two leaf, just with the order of studs and drywall reversed in the interior leaf.

how big of a prefab unit is manageable? if you've got 8 ft tall walls and want double 5/8 drywall, i'd think no more than an 8 ft section is feasible just b/c it might buck and twist and break just getting it into place. at the joint of each prefab section there will be two studs sandwiched together, put gg sealant in there? same at the corners, and then case the corners and joints in drywall or 1 by, with more sealant where it butts into the prefabbed drywall. maybe. but i wonder if all those regularly spaced exposed studs might introduce some weird effect?
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DrummerMan
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PostPosted: Sun Nov 30, 2014 11:18 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

What he's talking about is 2-leaf, just with the inner leaf inverted so the framing is exposed. This allows you to stuff that space with rigid insulation, saving the 3.5" of absorption you would've presumably been putting over your new walls if they were done the standard way. What you loose is 3.5" of air gap between your outer and inner leaf which gives you a little less isolation. It's a give and take between how much space is at a premium vs how much isolation you need.

I'm pretty sure the typical approach is to pre frame on the floor then add the sheetrock before lifting into place. I think the logic with the corners is that even though you might not have perfectly overlapping Sheetrock caulked as it would be if you could access it, you'll still have all those 2x4 which you can caulk the crap of before putting them together to insure a seal.

This is at least what I'm planning on doing on my upcoming garage build.



Another idea could be that, since you're building from the foundation up, could you frame the inner walls first? That way you could get access to the backside of those inside out walls?
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PostPosted: Sun Nov 30, 2014 11:44 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

Sorry, see that floid already said some of that much more eloquently than I did.
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losthighway
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PostPosted: Mon Dec 01, 2014 8:42 am    Post subject: Re: Have you made inside-out walls before? Reply with quote

Thanks guys. Your getting it, it is two leaf.

The concept of caulking the gap in the 2x4's for sealing makes perfect sense. That pretty much gets me, understanding-wise, where I need to be for the walls.

The ceiling I still don't get. On the one hand after the walls up, you should probably frame the ceiling the way you normally would. You could put the drywall on the normal part of the frame, but then I imagine sound getting through the cavities left open in the walls, and shooting up towards the outer, structural ceiling.

That said I can't imagine away of putting drywall on sections of ceiling framing, AND then putting that up. I'm thinking that's impossible.

And for the record, if you want to see what this looks like (from outside to in: drywall, frame with insulation in cavities, fabric stretched and nailed/stapled to the frame, slats of wood added to taste for some reflection to balance out the highs and keep the room from sounding too dark) you can look at how they build the new Bunker in Brooklyn. There are a ton of other examples, but for a lot of smart reasons it seems to be a pretty standard approach for pro studios. I'm just struggling with how to accomplish it.
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norton
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PostPosted: Mon Dec 01, 2014 11:03 am    Post subject: Re: Have you made inside-out walls before? Reply with quote

Why not just build walls and treat the inner surface? No need to finish the Sheetrock, if you cover it with treatment.

Are you running into ceiling height issues?

Inside out walls work really well when you need minimal isolation, and you are building a smaller "iso" room within a much larger room.
Other than that..... Not so much. I've built a ton of inside out rooms for clients. I wouldn't recommend them, unless physical space was really that tight.

Also a KEY consideration, since you mentioned a contractor.... Is ease of construction. If your contractor doesn't build sound isolation assembly's every day then you will want to make your plans as fool proof as possible. Not that it's that tough to do....but your isolation hinges on the assembly/execution. A few misplaced screws and your efforts can be sabotaged.

Hope it goes smoothly!
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DrummerMan
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PostPosted: Mon Dec 01, 2014 11:04 am    Post subject: Re: Have you made inside-out walls before? Reply with quote

That does seem like a quandary...

You've seen the Bunker's build thread, yes? I didn't look at every link they put up but it looks like standard ceiling construction, though I don't know that for sure. Also, they had a big warehouse of access to different sides of their framing.

Maybe John will come on and give you some thoughts, or you could pester him on his thread.
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floid
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PostPosted: Mon Dec 01, 2014 2:22 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

for the ceiling, you could run a beam thru the center and hang your prefab joist assemblies on either side. it's stronger, reduces the length/weight of each assembly, and makes it possible to prefab in the room - otherwise your full length joists are too long to work with inside the room they'll be resting upon.

i think it would be easier to prefab joists and a single layer of osb or decking, hang, and then cut strips of drywall to fit between joists. but that adds a LOT of perimeter to seal, and screwing drywall into the decking might compromise its sound barrier function.

at the end of each set of joists you'd have to place a purlin in the air gap above the wall plate and have a good redundant sealing scheme. prolly the weakest link.
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losthighway
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PostPosted: Mon Dec 01, 2014 3:54 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

norton wrote:

Inside out walls work really well when you need minimal isolation, and you are building a smaller "iso" room within a much larger room.
Other than that..... Not so much. I've built a ton of inside out rooms for clients. I wouldn't recommend them, unless physical space was really that tight.

Also a KEY consideration, since you mentioned a contractor.... Is ease of construction. If your contractor doesn't build sound isolation assembly's every day then you will want to make your plans as fool proof as possible. Not that it's that tough to do....but your isolation hinges on the assembly/execution. A few misplaced screws and your efforts can be sabotaged.

Hope it goes smoothly!


Good points. I haven't personally worked in an inside out room, so I'm not empirically certain. From watching some build threads for the new Bunker, Studio G, and the control room for Strange Weather I've seen all these cool looking rooms with fabric walls covered with wooden slats. I just thought, "Man. You start with almost no reflections, and then brighten the room to taste with some slats so it's not too muddy. It just seems like such a smart way to start with your mids and high frequencies under control."

My control room design is a little tighter than I wanted- because my wife wanted a carport after I get done tearing down the old garage to build my studio. How's that for a classic tapeopper challenge!

I figure if the walls to my control room ARE treatment, then I don't need to tighten things further (spatially speaking) by adding treatment to existing walls. I guess the biggest thing in making this decision is trying to get a cost/benefit sense of what I'm getting out of inside out walls, versus the greater ease of building out regular walls.

Thanks for your thoughts guys.
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norton
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PostPosted: Tue Dec 02, 2014 11:45 am    Post subject: Re: Have you made inside-out walls before? Reply with quote

Right on. The problem with inside out walls is isolation.

As in....you won't have much isolation.

Acoustic treatment is relatively easy to add to a room after the walls are up. If your contractor is not well versed in studio building techniques, you will be much happier if he/she builds a tight simple room.....that you treat later.

Also, on the acoustics front... You will likely save time, money and wind up with better results if your acoustic treatment is specifically planned for your finished space.

There are a bunch of acoustic calculators online, or in an App Store that will help out there. Unless your room is an irregular shape....then you'll need to do some acoustic analysis... Basically a noise signal/capture. The App Store is a good start. Then you'll know which frequencies are problematic...and what/how to tackle them.

In small rooms bass is always a problem. Rigid fiberglass won't do the job alone.

You mentioned liking the slat/slot look. Which is great, because those are Helmholtz absorbers, generally and they are very effective at absorbing bass all the way down. Limp membrane absorbers are also particularly effective for absorbing low low bass.

If you've got any specific questions feel free to pm me.
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JWL
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PostPosted: Tue Dec 02, 2014 2:09 pm    Post subject: Re: Have you made inside-out walls before? Reply with quote

Great advice here. Inside out walls are something invented (or at least popularized) by John L Sayers. Check out his studio building forum for a ton of detail on the concept.

Speaking broadly, the benefits of inside out walls are that they are good for small rooms where space is tight. They can achieve decent iso, if there are (for instance) 2 layers of drywall with green glue between, and each modular section of wall and ceiling is well made, attached firmly to one another, and everything is thoroughly caulked up. This allows you to get insulation in the wall itself to act as treatment.

The downside is that the drywall (on the outside of the framing) is closer to the next layer, especially if the outer leaf is framed with drywall on the inside (this could also end up as a 2 leaf system). The more airspace between the leafs, the better the iso will be, all else being equal.
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