Well, the staff at the International Code Council, who publish the
IBC, the most widely adopted model building code in the USA along with many other codes and standards, concur that scenery is indeed a structure and subject to the building codes and that in most jurisdictions the building official has the authority to inspect it and require changes or removal.
Now, saying it has to be built like "commercial buildings" is a little extreme. For instance, in the common case of being on a
stage in an otherwise enclosed and code compliant building, you can ignore wind and snow loads and other
safety issues dealing with weather, including just keeping the rain out. You probably can skip a lot of the sanitation and mechanical (heat and cooling) issues, as that is covered by the building. Electrical is temporary and for the most part, everyone accepts that the National
Electric Code applies and has allowances for stages and temporary conditions (albeit the
NEC temporary is different - 30 or 60 days?). Fire
safety has been addressed, so that basically leaves structure and
egress (
egress being the basis for guards, stairs, ramps,
etc.)
So, there are a lot of exceptions to railings and guards in the
IBC, in fact 7, and 5 1/2 deal with auditoriums and stages. We live and work in very unique buildings, with many more code exceptions than other occupancies. Stairs and ramps and
egress as well. Based on familiarity and training, and assuming you try to adhere to the
AEA rules, there probably isn't a problem with the ramps and
escape stairs and high platforms without guards. Doesn't mean you can ignore these issues or have tippy, wobbly stairs or allow non-performers to run around on your sets, nor can you ignore
OSHA regulations if the occupants are your employees, but this shouldn't be a hardship.
So that kind of leaves structure as a biggie. I don't think anyone will require a
platform to be as strong as a
stage, which is 125 or 150 psf depending on which edition of which code applies, but is a loading as strong as a bedroom in a single family
house, 40 psf, reasonable? I think you could maybe argue for even less, but 40 or 50 psf seems to be a common criteria. Deflection is tougher, because traditionally the building code was concerned about cracking plaster on the ceiling under if the floor deflected -
bend but not brake. Later it adopted a criteria for gypsum wallboard, which was less fragile. And comfort is an issue - people don't usually like bouncy floors (at least adult people) - so the codes still limit deflection for all these concerns - and we may not care how springy the floor is in the Juliet balcony, because the actress is fine and only there for a few minutes and isn't dancing.
I know I can find ply and other structural sheathing that has span ratings printed right on it. I can find tables that have "deemed to comply" criteria, designs and materials sizes that have been proven adequate by time tested use and accepted as adequate by the code development process. And I know that some folks have demonstrated by engineering and by testing other materials and methods. You may also find it useful to show that your scenery is built as described in published books and articles. It would be hard to say that what Parker and Smith said was OK for the last 50 years is not OK.
But frankly used 1/2"
MDF on 24" centers seems just too light, and unless the material was stamped with that span
rating for floors, I'd probably red tag it as well. And don't forget that span ratings of sheathing is often based on continuous application, and one whole 4 X 8 is stronger than four pieces 4 x 2.
And this has been ratcheted up as a result of the Indiana State Fair
stage collapse according to the ICC staffer who hears this from their building official members.