balustrades on balcony

Hi

I live in a block of 5 units and only two have balconies. One balcony is on title but my balcony is common property. Who is responsible for the water proofing and balustrades on each of these units balconies?

One member of the body corporate keeps saying the balcony that is common property, which is the one that i have access to, is not to be used as a balcony because it is a roof over the extension of her unit below.  we are unaware of what structure it was made of. Is it the body corp responsibilty to investigate and see if in fact their is a safety issue? The room below never had a DA lodged but it is on that units title, but no records on how it got onto the title. This owner does not want the balcony to be used because walking over it makes lots of noise so an inconvenience to this owner. She keeps referring the balcony as a roof and it is only to walk over. This space is 20m2 and at my back door and allows exit to backyard.  

Any help with assisting me with this area would be appreciated as I would like to water proof it as it is over 40 years old and replace the balustrades as they dont comply and are loose but dont want the responsibility of reinforcing a structure that was not council approved and is in need of repair. I dont have exclusive use however noone would use the space. 

The owners of the unit that has the balcony on title wants to put an awning up but when I ask for the same privilege I am refused because it is common property and it is a “roof” being the excuse.

My final question, I am prepared to  purchase the balcony space from body corporate and get on my title but I dont feel I should have to also pay for the repairs of the structure as well as the cost of putting up the awning.  What is a suggested best approach to get the repairs done and then purchase the air space. My unit is in Randwick.