Soundproofing my room... questions...

[Tmac]

I've built a room within a room in my detached workshop for band practice. I realize this forum deals with home theatres, but I think my questions still relate. I'm on a limited budget and am building as cheaply as possible.

My workshop has no foundation, and is simply raised about 2' off the dirt on posts. Single layer plywood floor, uninsulated. Wall are 2x4 insulated but not airtight by any means with metal sheating for exterior siding. Shop roof is not insulated but is high enough to have allowed me to build an 8' ceiling for the room. I built quickly without doing enough research as I had to take advantage of my father-in-law visiting as he's a carpenter.

My room is 2x4 with 1" gap between existing shop walls, r12 pink insulation, and osb sheeting on the inside for walls (I wanted to use up osb that I already had) --no outside layer (walls or ceiling). I used closed cell foam (plate gasket) on all studs and joists prior to screwing down sheating to minimize sheating contact to studs. I realize now that this probably has done little to isolate but I hope it helped slightly. I built a floating floor with 1/2" soundboard, and then 2 layers of 1/2" osb with lots of Lepage Acousti-seal (black tar like stuff) sandwiched between. Osb layers are screwed together with 1" drywall screws which don't go into the soundboard. The floating floor doesn't contact the walls and I've sealed the 3/8" gap with the Acousti-seal. I have installed underlay and carpeting. The ceiling of the room is insulated R40. I have a large window in my room looking into the shop with 2 thermo windows installed (one on inside, one on outside = double layer) which I had laying around. The door is solid and very heavy which I am going to seal with gaskets. I also plan on sealing the room completely with caulking.

Mistakes: wall plates are directly on the plywood floor; 6 elec. outlets cut into the sheating, 2 holes in ceiling for light outlets (as you would normally with drywall ceilings), and a bathroom exhaust fan with regular 3" plastic duct direct to outside. Window doesn't help but wanted to avoid a 'cave' like room.

So far, higher frequencies (vocals/guitar) are not too loud outside the shop but drums/bass are only slightly muffled.

Questions:

I am planning on adding a layer of 1/2" drywall (I know 5/8" would be better but it's almost double the price) to the osb walls with Green Glue sandwiched in between. Will this be worth the expense/effort? I have to keep all costs to a minimum.

I also plan on building some bass traps and absorption panels to mount inside on the walls/ceiling to improve acoustics. Any directions on how to go about building these?

How can I best reduce the negative effects of my mistakes without spending much $$ ? My main concern is to minimize sound escaping to my neighbours.

Any suggestions would be MUCH appreciated!

Thanks,
Tristan

[bpape]

1/2" w GG will still provide a good benefit. Anything you can do to pull old boxes out or just use putty pads in back of existing boxes will help

Bryan

[Tmac]

Thanks very much for the input Bryan. It gives me peace of mind knowing that going to the effort of adding the 1/2" with GG will help.
I've seen putty strips applied to the back of outlets on youtube but this would require me removing the associated osb sheating. Would expanding foam do anything if sprayed behind the outlets? All outlets are new as I need this many for equipment. If the foam is useless for sound dampening, where would I obtain the putty? I haven't seen it in any box stores (home depot or home hardware). Keep in mind I'm in Canada.

Again, many thanks for the help.

Tristan

[bpape]

Expanding foam will do little to nothing - just no mass there.

Not sure where to get in Canada. You can also try what's called Mortite. It's a brand name for rope caulk, kind of like modelling clay. It's used to seal window panes to frames.

Bryan

[Ted White]

Tmac, there is generally only a few pennies difference between 1/2" and 5/8". Check your numbers, maybe.

[bbieger]

Ted is right, the 5/8 should be less than $1 per sheet. Its ALLOT heavier per sheet. I used green glue sealant to seal my electrical boxes. Probably not as effective as putty, but much cheaper and for my situation.. better than nothing and effective enough.

Check out my thread : http://www.hometheatershack.com/forums/home-theater-design-construction/22601-monkeyboy-ht-build-2.html

to see the boxes I built and installed around my can lights. Not to difficult at all really. The system of hanging the boxes by wire and then installing the drywall worked really nicely although I was using a drywall lift which is advisable for 5/8.
Cheers,
Brian

[Tmac]

Ok, I'll look for Mortite. Thanks for that.

Ted, it seems up here in Canada drywall is much more expensive for the 5/8". I called everywhere in town and all suppliers except one were bang on $19.58 per 4x8 sheet compared to $10.29 per sheet for the 1/2". The last place I tried was much better at $14.40 for the 5/8 so I think I'll put out the extra $70 and go for it as I only need 14 sheets. I'll look into the lift if I can't get enough hands to help. Good advice.

As I already have the carpet and underlay in (just floating) and I'm not going to be mudding I don't think, I'd like to just let the drywall rest on it and install it that way. Is that a good idea, or should I be pulling it out to install the drywall and then re-cut and lay it?
How should I install the plugs in the drywall? They are already installed in the osb as you would normally in a drywall wall with the boxes on the studs.
Also, should I bother to caulk the osb seams throughout the room prior to installing the drywall?

Nice boxes Brian. What's the white insulation you used? I can build a couple of those and get up in the shop rafters which are just above my decoupled ceiling, push aside my pink insulation, and probably put them over the light outlets. As my 2x4 joists are totally decoupled from the shop rafters but the light boxes (outlets) are attached the them, the joist would have to become one side of the box. Gets a bit complicated so as I type, I'm thinking the putty would be much easier if I can find it. By the way, does it matter that the insulation comes up from the ceiling and sits in between the shop rafters, touching them? I figure the insulation won't be transmitting any sound, would it?

Cheers,
Tristan

[bbieger]

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[bbieger]

Wow that is pricey sheet rock!! My 5/8 was around $8 a sheet. Don't rest the drywall on the carpet you'll never be able to replace the carpet in the future. Give yourself a 1/4 inch off the carpet and cover the gap with your baseboard. Ideally take the carpet out but probably not a big deal. Seal osb? No.

Your outlet boxes will need extention boxes if your putting two layers of drywall up. If only one that not a big deal. Not exactly to code but just make sure your wires are nice and pushed into the box - not touching drywall and you will be just fine.

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[bpape]

Bryan