John Sayers' Design Forum

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PostPosted: Mon Mar 06, 2006 11:04 am 
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Location: Northern California
Hi folks,

1st post for me here. I'm considering a rebuild of my current studio and am looking at several ways to achive my goals. Salient points:

a. 26'x19'x13.5' finished room dimensions inside (1.9x1.4x1.0 ratio)
b. 32'x20'x15' outside dimensions, which will be 2nd floor over garage
c. mostly mixing and mastering, some tracking of acoustic to jazz levels, no heavy rock
d. video post production as well
e. neighborhood setting but rural, nearest across the road
f. existing outside walls will be kept and added to
g. new interior walls and ceiling on floated floor over 2x10 joists over garage

Except for the hardwood floor, all of the finished interior surfaces will either be absorptive (fabric over mineral wool) or diffusive (home made binary amplitude and quadratic residue diffusors), with minimal hard surface areas. With that in mind, I've come up with a proposed wall detail that has some advantages in cost and flexibility. I'm aware of some possible difficulties, but I'd appreciated some feedback from those more experienced than I to see if I've missed something.

The attached picture shows a section looking down on the existing outside wood stud wall and skin, with a new floating inside steel stud wall, with the mass (leaf) on the OUTSIDE. This leaves the whole inside stud cage a skeleton for mounting absorptive and diffusive materials.

Comments?


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PostPosted: Wed Mar 08, 2006 7:18 am 
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http://www.saecollege.de/reference_mate ... /Walls.htm

Look familiar? :wink: John sold that site to SAE several years ago...

The good thing about this idea is the saving of space, and some material savings; the downside is, when you narrow the air gap between inner and outer masses you LOSE isolation, especially at the LOW end where it's ALREADY difficult to achieve. Whether this works for you depends on your outside noise floor.

Also, you're floating a floor on an upper level? Have you calculated m-a-m for that floor, or are you designing a large drum head? :?

Love to see the rest of your design and discuss it... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...


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PostPosted: Wed Mar 08, 2006 10:58 am 
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Joined: Thu Feb 23, 2006 11:31 am
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I hadn't seen John's version of this idea, thanks for pointing it out. It gives me some reassurance that it's not too whacky an idea.

The reduced air gap is only in comparison to a full double wall with leafs outersides. My other reasonable option is a standard single stud wall with RC one side and gypsum attached, so this actually gains me air spacing wrt that.

As for the floating second floor, I realize it can get tricky, and welcome further discussion. But what other options are there, realistically, to isolate the upper studio from the lower garage which is attached to the rest of the house? I'm certainly open to suggestions?

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PostPosted: Thu Mar 09, 2006 11:28 am 
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Using the "Don't even THINK..." post at the top of this forum as a guide, check out/measure EVERYTHING you can about your existing construction; spans, spacing/centers, size of all framing members, type of sub floor and flooring, ad nauseum; post them all here so everyone can look for potential death traps, etc...

(and you're right, if you need great isolation from the house (and the garage is attached) you can't GET there without full room-in-room construction... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...


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PostPosted: Sun Mar 12, 2006 2:25 am 
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First, thanks for the response Steve. I'd like to hear first-hand experience from anyone who's actually built walls this way.

Although not the original owner, I'm fortunate enough to have the stamped plans for this house.

The current upper floor studio is 20'x20' over a 20'x30' garage, with a support beam and posts at the demarcation line. The garage walls are standard 2x4 with double top plates, on poured footings and stem walls. The garage has one 20' wall in common with the back of the house.

The current upper level is 5/8" plywood over 2x12 floor joists 16" OC. 5/8" drywall below. The span is therefore 20'. I've already consulted a structural engineer about my proposal and he believes there is plenty of support already there for the expansion upstairs.

So, how best to isolate the floor/room? My current thinking would be to rip off the plywood and float a 2x4 frame, on edge, that mimicks the layout of the joists, with cross connect pieces as needed, over neoprene (or the like) spacers. I'm thinking of filling the whole 2x12 cavity plus the 2x4 cavity with insulation, cable chases, elec wiring, and heating ducts, etc. Then several layers of plywood and/or gypsum on the floor finished with hardwood and carpet. Of course the new inner walls and ceiling would be supported by the floating floor as well.

Comments appreciated.

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PostPosted: Sun Mar 12, 2006 10:21 am 
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OK, first off if your actual, unsupported span with 2x12, doug fir #2 and better joists on 16" centers is really 20 feet (no supports in the middle or anything) then you barely meet the requirements for 30# live, 10# dead load as it is; dead load is calculated INCLUDING the weight of framing, and 2x12's on 16" centers adds at least 3 PSF to dead load; this leaves only 7 PSF for ALL OTHER materials supported by your joists. IF you have 5/8 wallboard under, and 5/8 ply above, the wallboard adds 2.4 PSF and the ply would add 1.8 PSF, for a total of 7.2 PSF as it stands right now.

Adding a 2x4 frame, supported by these joists, would add another .9 PSF, and a solid (non-concrete) upper floor would raise that another 6 to 8 PSF, which would put you over the rated span on your joists by about 5-6 PSF, making your floor dangerous BEFORE you add the weight of gear...

On top of that, using a wood floated floor doesn't get you into the low m-a-m resonance that stops bass; that takes something more like 3-4 inches of CONCRETE floated over a nearly equal mass.

If there's some way of putting a steel I-beam and posts down the center of the garage, perpendicular to the direction of your joists, you'd have more than enough strength to support even a floated concrete floor; but as it is, I'd not even consider doing what you're suggesting. It will not only be unsafe, but you'll still get flanking of bass thru structure and into the house... Steve

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Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...


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