Stand Alone Garage Conversion

[ap]

I have a stand alone garage in my back yard about 30'-40' from the neighbors. 20'x14' outside dimensions on a thick concrete slab.

Frame is 2x4's every 16''. 1/2'' OSB is nailed to the exterior of the 2x4's. The OSB is covered in Tyvek. And then Hardiplank siding is nailed on top of this. The interior is unfinished- when inside, you can see the 2x4's and OSB. There are french doors, about 5' wide together, on one long wall, and one short wall has a 3' door and two windows, each about 3'x2'.

Looking up, there is an attic space that has one of those pull down staircases. The ceiling is unfinished- you can see the 2x6 joists and the underside of the attic space's floor, which is 1/2'' OSB.

I would like to use this as a jam space and possibly recording of loud(rock) music.

I figure finishing the interior with a sandwich and possibly rigging up some kind of special door and window covers is an option but probably not soundproof enough if I want to play at night. What do you think?

So I'm leaning toward building a "room" inside this space, isolated from the building.

All comments suggestions welcome. Some thoughts:

1) Think I need to build another floor as well, isolated from the existing slab? Hoping the slab won't transmit much. It's about 12"-18'' deep around a 12'' wide perimeter, and 4'' deep inside that (monolithic slab). About 6'' is above ground.

2)If I go with a room inside room, what is optimal stud spacing? To see why this is confusing, check this link: http://www.saecollege.de/reference_material/titles/Acoustics3.htm

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Tyvek: thin, white, nylon-like tarpaper alternative by Dupont

Hardiplank: 3/8'' thick concrete siding, looks like wood siding once it's up and painted

 

[sjoko2]

First question is - where in the world are you? As this will have a bearing on the choice / cost of materials.

Second - If I remember the SAE files (John's work) shows a single garage conversion. Is that something you are looking for? Or do you just want a single sound"proof" room?

Third - Do you have a budget for this? Or does it have to be as cheap as possible?

 

[ap]

1)Central North Carolina. OSB and plywood prices vary with hurricane season- from about $5-$9/sheet for OSB. BTW, do you know if OSB compares favorably to plywood for soundproofness, STC?

2)Yeah, I saw the two garage conversions. My main reservation is dividing the room and the playing area getting too cramped for comfortable, regular practice. I should mention that I will have a couple of work benches in here as well. My plan is to make a single soundproof room, with a small vocal booth inside it.

3)I want to do it well, but don't have to go all out. I'm probably going to build it in steps as funds become available, one layer at a time. If I can get it soundproof by just putting some type of sandwich on the existing wall, I'll definitely go that route. If I have to make a room w/in a room, that's fine. I'll find the money eventually.

One thing I'm not sure about is angling the walls. Space is more a priority than acoustics. How much do you have to angle the walls to receive a benefit? Will it be a nightmare trying to treat a rectangular room?

Forgot to mention an air-conditioner in the short wall opposite the wall that has the door and windows.

 

[sjoko2]

"room in a room" would take a foot of your space, both in width and length.

First thing I would do is to see how far you can get with the existing structure, insulating and cladding the walls.

1 - buy a load of chaulk. Get the 30 or 35 year guaranteed white one, Home Depot is a good supplier, you can get them as a contracters pack. Thoroughly clean the innre frame from all debris, dust etc. Now chaulk all edges inside the frame, neatly. This will ensure two things. It will seal any possible gaps from nails etc., and it will prevent any possible rattles.
Also put a thickish line of chaulk on the floor around the frame.

2 - Find a good supplier of Rockwool (comes in 16" x 4' sheets to fit the cavities in the framing). Fill your cavities with the rockwool. 2 layers, leave no holes, overlap seams, take your time, do it right, wear gloves and goggles.
Do the same in the roof cavities. To keep it in place buy some packs of thin welding rods, cut them 1/2" longer than the cavity spacing. These will hold the rockwool in place.

3 - Screw a layer of thick OSB on the frame, the base resting on the thick roll of caulk you have placed on the floor. Screw the OSB on the frame with 1 1/2" gold drywall screws at approx 2' spacing. Do the same all around, including the ceiling.
Where there are joints in the OSB, make sure you seal all of them. Liquid nail in the gaps, when the liquid nail has dried, a small bead of chaulk spread with a putty nife.

4 - Staple a layer of 1/2" soundboard (the soft brown board) over the whole lot. Once again, start with a bead of caulk on the floor fro the board to stand on. Use staples which enter, but do not penetrate, the OSB. As above, seal all the edges.

5 - Finish it all with a layer of 5/8 fire rated drywall, nailed for first grip, then screwed. Make sure all seams are taped properly, and all nail / scew holes plastered over.

Now you'll have a good wall which will most likely be sufficient. If not, you apply another layer of drywall on resilient channel.

 

[ap]

So you think it's possible that a sandwich on the existing walls may be sufficient. I'd hate to do all that, still not be quiet enough, and end up building a room-in-a-room anyway.

Even if I tried the sandwich, wasn't happy, and built a room, the sandwich wouldn't be a waste since it's still contributing. However, if I decided before I started that a sandwich would not be sufficient and would have to go with a room-in-a-room, how much would I have to do to the existing walls first? Could I get away with leaving it just like it is? Put one layer of OSB on the existing wall? More?

I realize there's alot of educated guessing going on here. There's no way to answer for sure. But, is there any way to get a rough estimate with some calculation. I assume that STC must be some kind of coefficient you plug in an equation. i.e. decibels-in X STC=decibels-out. Does anyone know if such an equation exists?

Or what about experience? Can anyone describe some results they've seen from thorough sandwiching?

Rockwool and soundboard: Are these the common names for these things? Will the guy at Home Depot know what I'm talking about?

I notice on the SAE site that STC increases dramatically with resilient channel. Why not use that between every layer of the sandwich? Stuctural integrity?