Floating floor questions

[cadesignr]

Hello guys. I have some questions to clarify some things that I don't quite understand yet. I'm posting this drawing to illustrate what I am talking about. This is a section/detail for a friend, who wants to build floating floors/rooms in both a control room and studio. However, he has access to lots of lumber/ but no budget for floating a concrete slab. So here are my questions.
I've read most of the posts here, in regards to floating floors. However, I don't understand what makes ONE LEAF. IF, we were to build this floor with a BOTTOM whereby we could fill the voids between joists with kiln dried sand, and then screed it off, lay a visqueen layer, and fasten two layers of OSB, and a finish floor, would this ASSEMBLY then be considered ONE LEAF or TWO? I thought that since sand has density and weight, that it would dampen any resonance similar to concrete. The airspace between the floating floor and the support slab under it, would actually vent up into the airgap between walls, although the airgap as a whole would be sealed completely around all walls and ceiling. Is this overkill or plain stupid? Should we use insulation instead? And if so, then we shouldn't put a bottom on it, right? Thanks. This one has dumbfounded me for a long time.
fitZ

[cadesignr]

PS, this is an OLD detail that I drew BEFORE I understood about RC and double walls. Ignor it
fitZ

[knightfly]

Sorry it took so long Rick, been rebuilding one of the swing cylinders on my backhoe - just when I think I might actually accomplish something, this type of crap happens...

Basically if that floor is packed solid with sand, it's one leaf, made up of three layers; bottom plywood, sand, top plywood. - problems I see are too thin a bottom for that much weight (will sag over time, leaving an air gap between the top surface of the sand and the top floor layer) -

If you were to use 12" centers for joists and keep everything else the same, you would approach about 5" of concrete for mass, but your air gap would only be the thickness of the pucks; so in this case, I'd opt for thicker pucks, similar to what Paul's doing on studiotips with the 2" Sylomer blocks - this would improve the m-a-m resonance downward by probably 2 octaves over using 1/2" pucks, since m-a-m changes relative to air gap - every doubling of air gap lowers m-a-m by an octave,

Gotta hit the hay, 4:30 am comes early... Steve

[cadesignr]

Hey buddy, no problem. I understand your DDJ, and those unexpected problems. I have my share all the time So I REALLY appreciate you taking a little time for my question.

Ok, I'll beef up the bottom with 3/4 OSB, and blocking between joists at 24"oc, which should do it. The only thing I'm still not sure of yet, is the total wieght vs the springyness, and leveling the floor. Kind of difficult with a bottom on the framing, but I'll figure it out For all the work this will take, I want to get it right. I'll post a plan during the month, and see if I can find some weight schedules. I've never heard of the 2" Sylomer blocks, but I'll check them out too. I saw the thread here about them but didn't read it yet.

This is one of a couple of projects for some friends, and you know I'm no expert on this stuff. So I thought I'd ask you for advice. Thanks Steve. I do have some other questions, but no hurry at the moment. Get some rest and I hope you get the backhoe fixed.
fitZ

[knightfly]

Rick, you could still use 1/2" pucks for this; but if there's enough headroom, you will VASTLY improve the floor by putting 2x4 joists over the pucks, THEN doing your plywood "sandbox" as drawn. This would lower resonance by a LOT - using Insul in a sneaky way, I get roughly 40 hZ mam resonance with 1/2" gap between the lower plywood and the concrete; by increasing this to 100mm (2x4 + 1/2" puck, slightly compressed) the mam resonance drops to about 14 hZ. Definitely worth it if you have the headroom... Steve

[cadesignr]

FOURTEEN HZ!!!! You got to be friggin kidding! I couldn't be so lucky. Wow! See, thats what I tell folks. I'm guessing, Steve KNOWS his s..t. Well that is a real kicker. So, let me see if I got this right. We build a SUB-FRAME that is supported by the 1/2" pucks........WOW! I can level that FIRST. COOL!. Then we line this with insulation...right? THEN, we can build.....HOLY MOLY! Now I can break down the sandbox into MODULES! TOO COOL> .

...Steve. You are ...

[cadesignr]

Thanks Buddy. Have a great week.

Rick

[knightfly]

You too, man - finally got the hoe back in working order, got my tools put away just as it started to RAIN... (never fails ) looks like it'll be too wet tomorrow for what I want to finish up, but at least the machinery's usable again - here's a few pix (shot in the dark from under a large umbrella in the rain) First, the one rebuilt stabilizer cylinder - then, a close-up of the two newly rebuilt swing cylinders (the green rings are just the outer wiper seals, there's lots more inside) -then, the beast hisself -

Note the 4 holes outside the green rings on the end caps of the cylinders? These are for factory spanner wrenches I didn't have, so I built my own using 1/4" x 4" steel plate, and using a Re-Bar Bender for a cheater bar to get the gland nuts (end caps) tight enough -

To get an idea of scale, those chrome rods sticking out of the green rings are 2" diameter.

[knightfly]

Here's the home-made spanner pix - first, the dual-size spanner with the rebar bender in place for more torque; then, a close-up of one end of the spanner - each end is a different size, I made two of these and need to do one more (no two cylinders seem to use the same size end cap)

Bolts are 1/4-20 x 1/2" grade 8, the holes are tapped and the bolts run up til the heads bottomed out - this worked really well.

Only 3 more cylinders to do, not counting the 4 more on the hoe itself or the two front bucket tilt ones - fun is where you find it... Steve