Have I accidentally created a three-leaf floor here?

[bitmit]

HI,
New to the forum, and very glad to have found you all. I'm in the process of building a studio/writing room in my garden and not sure if I may have made a mistake with my design for the floor. I'll attach a sketch.

Floor construction is as follows, from the ground up: (1) Ground screw; (2) 6x2 deck joist; (3) OSB3 18mm; (4) Celotex 50mm; (5) OSB3 18mm. That makes for the deck construction, on top of which continues: (6) Cabin floor joist (and air gap); (7) Cabin floor board; (8) MLV or similar rubber matting; (9) Floating floor joist (with RWA45 in the voids); (10) 18mm ply and finally (11) Hardwood flooring.

My question is this - does the second OSB3 layer at (5) constitute a third leaf? If so, what would be a solution?
Secondary questions: Has anyone experimented with using stable mats instead of MLV? It's much cheaper pound for pound, and more mass. Also, can I fit a larger depth of RWA45 into the voids at (9) and just compress it down with (10) and (11)? Would it be worth the effort/expense?

Thanks for bearing with me, and thanks for being there!

John

[DanDan]

On a quick scan, it looks inordinately complicated. I don't know building practices where you are but why not lay a concrete floor 'on grade'
What are you trying to isolate from what?

[bitmit]

Isn't it just a simple Mass:Spring:Mass construction, with 3-5 being the lower mass, 6 the air gap and 7-11 the upper mass? That's what I thought I was drawing anyway. Please explain if it can be made simpler (1 & 2 are simply the deck upon which the cabin will be built). My concern is that in trying to give the lower mass more, er... mass, I've inadvertently added another leaf to the equation.

I'm a Film/TV composer, and just need a place to work at a reasonable volume without broadcasting to the neighborhood what I'm up to. I also (occasionally) record live instruments, and would like to not have to worry about ruining a take if the garbage truck goes by. It doesn't need to be NASA, but I'd like to get at least some bang for my buck.

I was quite a way into the process (in terms of purchasing materials) before I found the forum, though I haven't actually broken ground yet. I hadn't realized that a concrete bed was preferable, and was trying to avoid the work involved - hence the ground screws and 6x2 timber. I've already bought that stuff, but as I say I haven't begun construction. Should I really be re-thinking the groundwork?

[bitmit]

I guess my question is: Does the lower mass (3-5) constitute 1 leaf, or is the Celotex regarded more as an air gap? My reading is leading me toward the latter, but if someone could confirm that it would help me decide whether or not to abandon the idea and go with a concrete slab.

[John Sayers]

Go with the concrete slab.
cheers
john