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About to drywall workshop - do I need to fix/double check anything?

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Forum topic by ADHDan posted 06-14-2013 04:38 PM 1462 views 0 times favorited 36 replies Add to Favorites Watch
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ADHDan

588 posts in 829 days


06-14-2013 04:38 PM

Topic tags/keywords: question

I’m almost done insulating my workshop to minimize sound transferrance. I’m working on a standard framed interior wall with paneling on the non-shop side (a family room) and open studs on the shop side. Eventually, I’m going to replace the family room paneling with drywall.

For soundproofing, I put two layers of pre-cut styrofoam (.5” by 14.5” by 4’) in each stud cavity, separated from the drywall and from each other with a series of permiter screws. Thus, I’ve got five alternating layers of air pocket/styrofoam. I cut and roughed in the styrofoam as best I could to fit around electrical and cable cords and boxes. Now, I’m about to start using a spray-foam (this stuff: http://www.homedepot.com/p/GREAT-STUFF-16-oz-Gaps-and-Cracks-Insulating-Foam-Sealant-162848/100003351) to seal the edges and gaps. Once that’s done, I’m putting up two layers of drywall.

I guess my question is simply, have I overlooked anything really important that needs to be addressed before I start doing quasi-irreversible work? Everything I’ve done until now could be easily dismantled and checked/fixed, but once I spray in the sealant it will be a lot more difficult. Is there anything I should know or check regarding the wall-cavity power and cable lines, or any structural issues I should be aware of?

Images below to show you what I’m working with. Thanks!

-- Dan in Minneapolis, woodworking since 11/11.


36 replies so far

View PurpLev's profile

PurpLev

8476 posts in 2369 days


#1 posted 06-14-2013 04:44 PM

curious – why double drywall? are you planning separating the 2 drywall layers from each other with an air gap?

Another thing that came to mind – if you seal gaps with spray foam, won’t that in effect anchor the styrofoam to the studs and limit their vibration efficiency which could in effect transfer more sound? (to be clear – I do not know this either way, just a thought that came to mind… )

what made you plan it out this way?

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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jross827

1 post in 587 days


#2 posted 06-14-2013 04:47 PM

To be honest, if it were me, i wouldn’t put up drywall at all.. I would just screw on plywood or osb sheating. It gives you the ability to hang stuff wherever you want, and you could take it down somewhat easily if need be if you had to run a new 220 line or something in the future.

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johnstoneb

768 posts in 893 days


#3 posted 06-14-2013 04:52 PM

I think code requires double thickness fire rated with joints staggered between uninhabited and inhabited spaces.

-- Bruce, Boise, ID

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MrRon

2928 posts in 1964 days


#4 posted 06-14-2013 04:53 PM

Have an electrician check your wiring before closing up. If you are going to plug in machines, make sure the wiring is a minimum of #10. You can use #14 for lighting (ONLY). # 12 is better. In your last picture, I can see two BX cables near the ceiling that should have penetrated the top plate. If you can’t reroute the cable, you can notch out the plate and cover with an 18 ga steel plate. An electrician will point all of this out to you

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ADHDan

588 posts in 829 days


#5 posted 06-14-2013 04:53 PM

PurpLev – from what I’ve read, two layers of drywall offers more mass and thus more sound barrier than one. Is that not accurate? Also, I don’t know one way or the other whether it’s better to leave the styrofoam unsealed, so if you (or anyone else) knows the science there that would be great.

This plan was suggested by a professional woodworker friend when I asked him for relatively cheap ways to (sort-of) soundproof a workshop. He suggested the alternating layers of air/styrofoam, with two layers of drywall. I thought about using resilient channels, but I need to hang cabinets and that would short-circuit the RCs.

jross – Drywall is a lot cheaper than plywood, and I believe it provides better soundproofing. Also, I plan on running French cleats along the wall for a modular approach to wall storage.

-- Dan in Minneapolis, woodworking since 11/11.

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PurpLev

8476 posts in 2369 days


#6 posted 06-14-2013 04:54 PM

OSB is good generally for hanging stuff on, but may not be ideal for sound barrier when compared with drywall.

on a side note – I worked on a home-theater room some years back. it was adjacent to the living room, and for sound insulation all I can remember is that they had a double drywall – and <maybe> insulation between the studs (cotton looking insulation) and with the sound (my install) at high volume nothing was transferred outside that room.

so I think you might have over done it – but better overdoing and having it work then not doing enough and being disappointed.

-- ㊍ When in doubt - There is no doubt - Go the safer route.

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ADHDan

588 posts in 829 days


#7 posted 06-14-2013 04:54 PM

MrRon, that’s a really, really good idea, thanks. I just called my contractor, who does everything – construction, plumbing, electric. He’s going to be at my place hopefully tonight or tomorrow to review my work and my plan, and let me know if I’ve created any danger of burning down my house.

-- Dan in Minneapolis, woodworking since 11/11.

View Charlie's profile

Charlie

1064 posts in 1006 days


#8 posted 06-14-2013 05:08 PM

If you don’t isolate the drywall on the shop side, from the studs, pretty much all of your Styrofoam does nothing but fill a void. The drywall on the shop side if attached directly to the studs will transfer to the panelling on the non-shop side using the studs as springs. The styrofoam doesn’t do much. A better choice there would have been Roxul (mineral wool) if you’re trying to keep costs down. It’s a much better sound insulator, but you still need to run some hat channel on the shop-side studs to separate the shop wall from the studs. If it’s too late to do anything about the styrofoam or if budget doesn’t allow for it, then at LEAST run the hat channel on the shop-side. And seal EVERYTHING. Even the space around an electrical box will transfer enough sound that you may as well just leave the door open. :)

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ADHDan

588 posts in 829 days


#9 posted 06-14-2013 05:14 PM

Charlie, will bolting cabinets to the studs and/or using French cleats (also to the studs) short circuit the channels?

Edit – I am also planning on running 1/4” foam padding (like underlayment) along the stud edges, between the studs and the drywall. And I did check with multiple sources who said that the styrofoam plan would work about as well as rock wool. (Hopefully they are right!)

-- Dan in Minneapolis, woodworking since 11/11.

View MT_Stringer's profile

MT_Stringer

2063 posts in 1951 days


#10 posted 06-14-2013 05:50 PM

I think you need more elect outlets now, not later when you will regret it. Do it. You can thank me later! :-)

-- Handcrafted by Mike Henderson - Channelview, Texas

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Charlie

1064 posts in 1006 days


#11 posted 06-14-2013 05:53 PM

Hat channel is just made to isolate your wall board of choice from the studs so the wall doesn’t pass vibration to the structural members. So not sure what you meant by “short circuit”. If you put foam padding on the studs and then compress it between drywall and stud, you’ve essentially removed its effectiveness almost entirely. And don’t get me wrong, I’m not saying the styrofoam is useless. I’ve done it. It just doesn’t compare to the roxul (I’ve done that too). Roxul is pretty dense but has an open structure. You can cut it with a bread knife. So it’s not the “rock wool” that looks like fiberglass. There’s also actually a paint-on membrane you can put on your first layer of drywall before putting up the second layer.

There’s all kinds of tricks and some are just more expensive than others. In the end you do the best you can and hope for the best result :)

Without knowing more about the how the “noisy room” is situated among the “not-so-noisy rooms” it’s kinda hard to make specific suggestions. AND… it appears I’ve arrived a bit late to this party anyways hehehe.

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brtech

696 posts in 1643 days


#12 posted 06-14-2013 05:54 PM

I did a bit of Googling, because I’ve never thought of styrofoam (expanded polystyrene) as a sound isolator. There are some who claim it helps a little, and others who say it hurts:
When one uses polystyrene in a cavity as partly filling you will DEGRADE the acoustic TL properties of that wall.
Since closed cell it will decrease the air cavity making that air spring stiffer thereby increasing MSM which not only influences the frequency of the resonant frequency in itself but the whole subsequent TL curve, which is related to that resonance frequency.

From that point of view your dad is right: it does exhibit some soundproofing properties: it makes that wall significantly worse (even when compared with an empty cavity).

If you make it into a glued/bonded sandwich panel, it acoustically starts behaving quite different and is not related to traditional drywall discussions here.

Rockwool is the recommended material. Mass helps, so the double thickness of drywall is a good idea. Isolating it from the studs is a really good idea.

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ADHDan

588 posts in 829 days


#13 posted 06-14-2013 05:55 PM

I’m actually good on electrical outlets on that wall, since that wall is pretty much going to be used for cabinets and storage. I’ll put in more outlets along the opposing wall, though – that’s where my benchtop/stationary tools are going. Except for the table saw, of course.

-- Dan in Minneapolis, woodworking since 11/11.

View sixstring's profile

sixstring

296 posts in 963 days


#14 posted 06-14-2013 06:22 PM

Coming from my experience in building music and rehearsal studios, the BEST method of isolating sound is through mass and separation. If you could build a box inside of a box (ie. two framed walls with an air gap in between) and have as much mass as possible on the walls, you can almost achieve complete isolation.

With that said, we rarely have the space to afford the box in the box method… but using double thickness material (drywall or plywood or both) helps tremendously. Personally, I think it’s best to seal every possible way that air and sound can escape… This also solves the problem of dust traveling in between the spaces involved.. especially if it’s a family room. Things like bass traps in the corners can really tame the thumping bass from kick drums and bass amps… likewise, it will tame the abnoxious noise from compressors and planers and while it may still be audible outside, having the low and high frequencies tamed will make it seem far less annoying and noticeable.

And you are correct in thinking that styrofoam is NOT a good method of trapping sound. It doesnt have the mass. Rockwool, if you can find it, is the material of choice because of mass per square inch (density) and it’s availability/price. It’s more common in Canada and colder parts of the region for the same reasons. Otherwise, Owens Corning makes a similar pink product with nearly the same density/properties. Forgot the name though… it’s what I used for my bass traps in my own studio. Foam is best for controlling higher frequencies and has it’s own place in acoustical treatment… but nothing to do with sound isolation. The whole egg crate on the walls idea is nothing but a fire hazard and a way to store eggs on your wall.

There’s my 2 cents on acoustics.

-- JC Garcia, Concord, CA : "It's easier to ask forgiveness than permission..."

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ADHDan

588 posts in 829 days


#15 posted 06-14-2013 07:15 PM

Well, it sounds like the general view is that styrofoam is not the best sound insulator, which is bad news because I’m just about done with the styrofoam insulation and I don’t have the budget right now to redo things. The good news, however, is that eventually I’m going to be replacing the paneling on the other side of the wall – which will give me a second bite at the apple. I can leave the styrofoam for now and see how bad the noise bleed is, with the styrofoam. If it’s livable, I can just leave the styrofoam in when I redo the paneling; if it’s bad, I can swap out the styrofoam for a different product at that point. (As long as my contractor gives the ok on the current setup.)

Does that make sense?

-- Dan in Minneapolis, woodworking since 11/11.

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