Ways of adding mass

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losthighway
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Ways of adding mass

Post by losthighway » Sun May 24, 2015 6:10 pm

So while I wait for the endless rainy spring to dry up enough around here to pour the foundation so we can start framing, I have more time to think.

In sticking to the more mass formula of absorbing sound I pictured myself adding leaves of drywall between the studs of my outer wall, like many people have done to get two layers of mass on their outside walls. I've been preparing for a long and laborious month of cutting drywall, furring strips, backer rod, caulking, dust, sorrow.

And then I realized I'm building from scratch. Is there any reason just putting another layer of OSB on the outside won't work just as well, if not better?

We can stagger the seams, the cost is close to identical, and it will speed my build up by at least a couple weeks. Thoughts?

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Post by JWL » Sun May 24, 2015 11:38 pm

Mass is mass. If you are building from scratch then you can do things more efficiently than if you are building onto an existing structure.

Make sure you have a 2-leaf, Mass-Air-Mass system with your outer walls. This is hugely important in terms of isolation:

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Post by norton » Mon May 25, 2015 2:48 pm

Add another layer to the outside. It'll be fine, new energy models show huge benefits to an exterior layer of insulation as well.

Some sort of non compressing board based styrofoam. In case heating/cooling is on your radar.

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Post by losthighway » Tue May 26, 2015 5:12 am

Thanks guys. Yeah, definitely got a room within a room thing happening. I'm about to buy a lot of OSB. My carpenter keeps coming back on the adage that my "garage" studio is going to be built like a "brick shit house". He's thinking it will be the best place to hide during a tornado warning.

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Post by Flight Feathers » Tue May 26, 2015 8:05 am

Well, if you are building from scratch, you have a lot of options. I would get some numbers on density, there are probably materials that have more mass than OSB. For example, for your exterior wall, you could do OSB and then cement board. Or OSB-drywall-OSB sandwich. If you are working with a contractor, they will look at you like you are crazy, but that's a lot of mass you'll be getting on the outer leaf. And it will be really easy to put up. Much easier than stuffing the stud bays with drywall.

Probaby the best option are the foam blocks you fill with concrete.

If you are doing this with permists, figure out what you are allowed to do. Also, do some calculations on the mass, and figure out how much load your framing can carry. 16" on center may not be enough, might have to go to 12" on center.
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Post by roscoenyc » Tue May 26, 2015 9:59 am

In the "what the, huh" column,

What's OSB?

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Post by losthighway » Tue May 26, 2015 12:50 pm

It's basically plywood. Construction speak.

Here's my turn: Feathers, when you say 12" on center vs 16" on center are you talking about the gaps in the studs?

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Post by Flight Feathers » Tue May 26, 2015 2:17 pm

yeah, it refers to the spacing of the studs. 12" on center means the distance between 2 studs is 12", measured from the center of each one.
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Post by floid » Tue May 26, 2015 5:52 pm

ICF would get you the biggest mass bang for buck, but also has a much larger footprint than a stud wall. if the prints are drawn and forms staked, it may be a bit late to consider.

What thickness OSB? Around here it's typically 7/16 wall sheathing, 9/16 roof decking, and 23/32 floor decking. But i think you'd want the 23/32. just not the t&g variety, unless you're certain you don't need to allow for expansion at the seams.

How are you finishing the exterior? Hardi panels aren't terribly attractive, but they are dense.

I'd want to make sure multiple layers of sheathing don't present an added risk of moisture retention.

As for stud spacing, a typical 16" center exterior wall carries sheathing and siding outside, drywall inside, plus ceiling and roof assemblies. You're subtracting the drywall and at least part of the ceiling assembly, transferring them to the inner leaf, yes? And bear in mind OSB has some structural properties itself. My gut tells me there isn't a major issue here.
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Post by norton » Wed May 27, 2015 7:05 am

What's your goal as far as isolation goes?

A room/room scenario is pretty tough to beat. Unless you are going "in all the way" floating your concrete slab, you'll see very little benefit by continuing to add mass to the shell of a room within a room system.

High 50's as far as stc goes is going to work wonderfully. The only time you'd need to go the extra mile is if you were constructing an acoustic testing facility or building next to a train track.

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Post by losthighway » Wed May 27, 2015 11:46 am

Yeah, my goal is: as good as possible.

Residential area, won't be working after 9:30, I'm just throwing as much as my budget would allow. I record a lot of bands with loud tube amps, so I'm hoping it can be nearly inaudible from other folks' property. It's also a rehearsal space for my band.

Both the Iso and the Live Room have their own walls/ceiling. Not floating any floors or anything crazy like that. The mono slab is isolated, about 40 feet from my house and at least a hundred to the nearest neighbor. Insulation in both walls, double drywall, green glue, that kind of stuff.

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Post by norton » Thu May 28, 2015 6:07 am

You won't need anything else.

Going any farther will be a waste of money and effort. In order to justify more isolation, your slab would need to be floated on springs and isolated from the ground it sits on.

Kick drums and cranked svt's are the problem.

Just for reference, my personal studio space is residential, concrete foundation, steel stud inner walls with resilient channel and green glue Sheetrock on walls and ceilings.

I've got a large doubled up window that's about 6'x4'. Yesterday I had an impromptu jam happen while I was outside the space. It was sprinkling outside, and the rain was louder than any sound making out of my space.

Your studio will most likely outperform what I've got going....so you should have zero worries! Keep us updated. Pics etc. Looking forward to seeing it!

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Post by mn412 » Sun May 31, 2015 3:49 am

JWL wrote:Mass is mass. If you are building from scratch then you can do things more efficiently than if you are building onto an existing structure.

Make sure you have a 2-leaf, Mass-Air-Mass system with your outer walls. This is hugely important in terms of isolation:

Image
If you're doing the double stud thing I've read (and it makes sense to me) to stager the studs on the different walls. Basically you would have a 2x4 from one wall or another ever 8 inches instead of doubled every 16 inches.

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Post by losthighway » Sun May 31, 2015 10:35 am

Yeah that's one of the many things in this that you can't totally verify if it works, but it's easy enough to do it won't hurt anything. If there's a chance that it'll help I might as well plan the framing that way.

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Post by JWL » Sun May 31, 2015 10:43 am

mn412 wrote: If you're doing the double stud thing I've read (and it makes sense to me) to stager the studs on the different walls. Basically you would have a 2x4 from one wall or another ever 8 inches instead of doubled every 16 inches.
Staggered studs isn't a bad approach, but it's not the same as a 2-leaf, mass-air-mass, room-within-a-room approach. The former is an improvement over conventional construction techniques but the latter is better.

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