basement studio floor construction options

i'm preparing to build a floor in my basement studio and am not certain which construction method will yield the best in terms of tl and flanking A: glue and fasten treated 3/4 plywood directly to concrete slab, layer of GG and then 3/4 mdf with finished harwood on top. this would create one thick leaf B: glue and fasten (sill seal?) treated 2by4 flat every 16" on center on concrete slab, insulate with fiberglass, 3/4 ply, GG, 1/2"mdf, finished laminate wood flooring here's some info; basement is below grade in brooklyn ny condo building, other unit shares slab separated by my hallway and thick walls(2 layer 5/8 fire drywall on each side of wall) studio is 10'/18'/8'2" with two walls anchored into concrete and 2 layers 5/8 drywall(shared with rest of my basement area) 2 walls concrete and masonry shared with (1next building) and (2outside area), also below grade with large retaining wall 8' away. floor is concrete slab probly 3-4inches thick, i plan to rest inner walls of 2x5/8 drywall on the floor that i build moisture not an issue, but i've ruled out sand floor and floating or doing anything to the existing slab my goals are as much isolation from the condo that shares the slab as i can acheive. i do own a drum set. i'm not planning on playing it at night. these two ideas are within my budget and capabilities, but i don't know which would be better. any thoughts? thanks so much and new ideas welcome too :)

The more I learn about this stuff, the more I conclude that a slab that has firm contact with the ground is not a very good conductor of airborne noise. It's dampened by the earth it sits on. The walls have to be amazingly thick and heavy with a very wide air gap before such a floor can become a "weakest link" in the transmission loss. I'd say the bigger concerns are water intrusion and structural integrity in general. The only reason I personally did an isolated slab was that I had to pour a new slab anyway, so the thought was, why not isolate it at the same time? Knowing what I know now, I'm not sure I'd have done it the same way. I probably would have just poured a new slab and made sure it was good, strong, thick, reinforced, level, and smooth, forgetting about isolating it. But, who knows... ;-) --Keith :mrgreen:

thanks for the thoughts keith, i guess i'm more inclined to frame a floor and insulate it to add to the comfort of the studio, to match the floor height of the rest of the basement, and to add a little flood protection in case the sump pump fails. that noted, is a two leaf floor system undesirable because of resonant problems? there is no clear info about this, in rods book he recommends sand filled cavity floors, but no mention of fiberglass filled floors. any thoughts anyone?

The sand is to damp the floor and add mass - if you're gonna do a wood framed floor you want to use the tallest frame you can to increase the air gap, lowering m-a-m resonance frequency use the heaviest boards you can for the floor deck, for the same reason use GG between layers for even better damping use 3 to 6 PCF rockwool or fiberglass (not regular house insulation) under the floor, and fill it enough so your first layer of decking just BARELY compresses the insulation enough to fasten the panels to the frame; this also for damping. Anything less and I hope you like the "boom-boom;s"... IF you intend to actually FLOAT such a floor, add my comments on the first page of Aaron's thread to the reading list - http://www.johnlsayers.com/phpBB2/viewt ... 39&start=0 HTH... Steve