An "improvement" must be depreciated. A "repair" can be expensed. The difference is that a repair maintains the property in as-was condition. An improvement, also referred to as a "betterment", improves the value of the property and/or extends the useful life of the property or one of its subsystems. (Hence, replacing a 50 year old furnace is an improvement because it extends the useful life of the HVAC system even though it might not get you a better sales price.)
To me, "replacing" a structurally unsound balcony sounds like an improvement and not a repair. But you are the person who will have to prove their case to the IRS if audited.
