Pergola on title

Hi…we are new to strata living…..our unit has a wooden deck with a wooden pergola structure built over it. Our title deeds say we own the deck….do we own the wood on the deck and the wooden structure built over it.? We want to put a roof over existing structure….do we need body corporate permission? Can we remove part of the balustrade to gain entry into the common garden property? Do we need permission to do this?