To Rock or not to Rock

[knightfly]

From the pix, it's at least an 18 foot span those 4x12's are across; probably more. I don't have time to calculate the beams ATM, but the 2x4's on 24" centers at that length will support approx. 8 PSF dead load; if this is a flat roof, it's likely the plywood is at least 3/4", more likely 1-1/8. which weighs about 3.3 PSF by itself; so your roof, not including the 4x12's, would weigh about 4 PSF; I'm guessing (you can help here) that over the plywood is some kind of flatroof product, depending on age it could be tarred roll roofing, or?? Another couple of pounds per square foot, bringing you up to 6 PSF.

Adding even ONE layer of gypsum between the 2x4's would raise this another 2.35 PSF, putting you at 8.35 PSF roughly; this would be the ABSOLUTE MAXIMUM this roof could support, and that's ONLY if those 4x12's aren't already over spanned.

We need EVERY measurement you can give on each part of your building before going any further with this - As it stands, I wouldn't recommend adding ANYTHING to the ceiling except a thorough caulking with acoustic caulk; then I'd build inner walls (what's the floor, in INTIMATE detail?) and support an inner ceiling on those walls, strong enough to support full insulation fill and 3 layers of gypsum.

Details, every one you can think of - length of each and every piece, sizes, spacing, what's under them, etc -

Next (or first) do you have a Sound Level Meter? You'll need one, and not just to figure out how loud/quiet you need things... Steve

[WiseMindsRecordingStudios]

Thats basically what I said 6 posts ago.

[fisher of men]

Thank you for your reply,
room is 23' wide 57' long 13' to the bottom of the 4x12s
this area will be the control room and the studio room
the floor is concrete
the 4x12s are 23 ft long on 8'centers. they are actually 4x13
roofing is tarred roll
the plywood is 1/2"
I don’t have an slm meter. Ill try and get one.
I was hoping to be able to add 2 layers of drywall
to 8' long 2x6s ran in between the 2x12s using joist hangers
since those 2x4s may not be strong enough
to hold any more weight....
SO....Option 2 , It looks like i may have to build
a ceiling attached to my double walls.
that will also be tough to do with a 23 ft span.
thanks for your help, steve

[knightfly]

Thats basically what I said 6 posts ago

True, Andy, but good advice is worth repeating, 'speshully if it keeps a fellow musician from becoming (not so Grateful) dead

(Maybe if/when I get a slowdown I'll have time to read all of each thread before answering; naahh, prob'ly not)

[WiseMindsRecordingStudios]

LOL.... nod.