Garage Studio flooring

Hello, I've been lurking for a while and have finally gotten the nerve to sign on and show myself. First of all, thank you so much for providing such a wonderful resource. I'm amazed at the dedication and generosity of the participants here. For every person you know you've helped, there are probably a dozen you'll never know... I'm in the planning stages of building a studio (1 CR, 1 tracking room) in the attached garage of my house. The space is approx. 20'x30' with ceiling height of 10' and a concrete floor. The house is on the side of a wooded mountain near Harrisburg, PA. The closest neighbors are approx. 85 ft from the house. The house is a ranch style with the garage sharing a wall with the living room and kitchen. I record mostly straight forward rock with occasional drums, singer-songwriter, and some instrumental (classical guitar type) music. I usually record on weekends and evenings, not past 11:00PM. My goal is for my wife to be able to watch tv in the living room without hearing what's going on in the studio and also to not disturb my nice neighbors. The studio walls and ceiling will be detached from the house structure (2-leaf, M-A-M principles) My budget for the entire studio is around $8k. I'm trying to decide whether a floated wooden floor (I've ruled out floating concrete for several reasons, including cost and toil) will be a benefit for my situation. The cost of the semi-rigid insulation, as well as a second layer of 3/4"OSB are preventing me from fully committing to a complete floated wood design. I'm considering doing a lesser design (2x4's or 2x6's on neoprene with 16" centers, 3/4"OSB + 1/2" OSB or similar material, standard insulation between the joists). There will be hardwood in the main recording room over top the subflooring. However, with this design I'm concerned about the low frequency resonance issue. My question is: Would I still achieve my isolation goals and better acoustical design within the studio if I skipped a floated floor altogether? If so, what would be the best foundation for the flooring? Thanks in advance for any help you can offer. -John McGinley P.S. I'm attaching (hopefully) a basic sketch of the current plan.

Sorry, the jpeg wouldn't take, attached is the sketch in PDF:

John, welcome to the "posting" segment of our membership :wink: ON the floated floor thing; it's my opinion that if you can't do it right you're better not doing it at all, for just the reasons you've stated. Keep in mind, however, that at $75 a yard for concrete (not sure what it costs where you're at) the concrete to do a 3.5" thick slab costs the equivalent of a 4x8 sheet @ $26 each - that's about 1/3 the cost of a single thickness of 1-1/8 TG flooring plywood. Add the cost of a single layer of 3/4 OSB under that, subtract the cost of your 1/2" layer, and the concrete would only add about $10 per 4x8 section more than using a layer of 3.4 and a layer of 1/2 OSB. Of course, there is the small matter of back-breaking labor... :cry: You may find, depending on your existing construction, that NOT floating the floor may cause flanking noise into/out of the house area; if there is no way to "disconnect" the garage floor slab from house structure, then you may not get the isolation you (and your wife) need - please check the REFERENCE section, further down there are a couple of links to info on flanking that may help on this. If your house shares concrete structure (like, a perimeter foundation that's in contact with the garage slab) but does NOT use a slab floor in the house itself, it could be either better or worse for noise travel; sound travels pretty well in concrete, and can continue through floor framing/wall framing, finally radiating through vibration of wallboard and floor sheathing. Without a precise drawing of what connects to what (and how) it will be nearly impossible to gauge how bad this will be in your case. One way to handle this; build double frame walls, removing any wallboard that would cause it to be triple or quad leaf, get it finished enough to be sealed like it will be, and see how your isolation to the house is doing; if it's a disappointment, and you can determine it's due to the floor, you can float a concrete floor AFTER the walls are up; just keep it 3/4" away from your inner walls, use Celotex perimeter board to keep the floor frame from contacting any walls solidly, and caulk around the celotex after. Just a thought. You mentioned using Neoprene for floating; don't do that unless you intend to dismantle the floor within 10 years; EPDM is more expensive, nearly identical in isolating properties, and will last approximately 25 years at proper loading of around 15% (5% is minimum recommended, about 20% maximum for good life) HTH... Steve

Steve- That's great, thanks. I think I will do the floor last. That will give me the most flexibility for change or adjustment later. The ceiling will rest on the walls. Would it be best to float the walls/ceiling on the EPDM, or just set them straight on the concrete and caulk with acoustic sealant?

I'm still 'way too far away from being a vibration engineer (or even playing one on TV) to be comfortable trying to second guess what a particular elastomer will do to shear behaviour on a floated wall, so won't recommend anyone do that - there is a distinct possibility that you will make things worse instead of better, by inadvertantly choosing dimensions/properties of elastomer that will AMPLIFY audible resonances. For that reason, I would stick to putting a layer of "sill-seal" or similar material under sole plates, if that. The main thing is the hermetic seal between inner wallboard layers and their mating intersected surfaces. The sill seal would only ensure no rattles between sole plate and concrete should any fasteners not be tight enough, or the plate too warped to conform to the concrete. I have a 2" thick book on Vibration Engineering, but the damn thing won't read itself to me (preferably while I'm getting my full 5 hours sleep) and 'splain when I say "??!#@!? Whaaa...??" - So, it may be a while... :cry: If you leave the 1/4" gap between intersecting surfaces we recommend, caulking each layer with real acoustic caulk (NOT LePage, please) you will partially decouple the wallboard from the frame (other than at the very perimeter) which will help isolation quite a bit. HTH... Steve