OK, so I'm needing to construct a soundproof "room within a room" on the top (7th) floor of an office building. It'll be my 3rd music studio in 27 years, and my most ambitious. After consulting with an acoustic engineer as well as a structural engineer, it appears that the elevated slab needs to be 100mm of concrete resting on rubber mounts to create a 100mm air gap between the existing and new slabs. The inner walls and ceiling will probably need to rest on this new elevated slab. The area of this room will be 35 m2 (7 x 5) with walls around 2.8 M high. While the density of the elevated floor will be approx 250 kg/m2, the walls and ceiling need only be around 30 kg per m2. I've done some rough calcs:
TOTAL WEIGHT OF ADDITIONAL DEAD LOAD- 10,562 kg divided by 35 m2 - 302 KG
IF max load according to the Structural Engineer is 650 kg/m2 and ADDITIONAL DEAD LOAD is 302 kg, then remaining LIVE LOAD will be 348 kg. ( Is the requirement 500 kg / m2?)
MAXIMUM expected LIVE LOAD (drum kit, piano, 4 amplifiers, instruments, cases and 7 people ) = only 28.5 kg /m2 .
I need to go back to the structural engineer with this info and fear that he may not permit this design given that we are eating too much into the required Live Load. If this is the case, then I'd lie to explore other options that will work, remembering that the floor absolutely needs to be that heavy if it is to properly keep loud drums out of the Lawyers offices downstairs. There are no other neighbours on my floor to be concerned with.
Please see the diagram below. Note that the grey areas (the drum room and 3 booths) have the 100mm concrete floor whereas the white area does not. The diagonal broken line represents my idea that a steel beam could somehow offer support for the heavy internal structure, making the Additional Dead Load permissible, maybe.
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Understanding that it is not possible to have access underneath the existing slab, such a beam would have to run over it . My question is: does this beam need to go from corner to corner (I'm presuming there may be columns in the corners?), or can it just go from edge to edge straight across and still do the job? What kind of steel beam? How high would it need to be? Could it be brought in, in smaller parts and welded in place and still be strong enough?
Last question (I promise!), if this idea is viable, then would such a steel beam be placed directly on the existing slab, with the rubber decoding mounts placed on top? (with the new slab on top of the rubber). Or is it better to place the rubber mounts on top of the existing slab with the steel beam on top of it along with other perimeter formwork to support the new floating slab?
Not sure if this makes sense, but I'm happy to supply much more detail should anyone out there wish to humour me!
Cia for now.
StructuralBIMGuy
princeplanet
