Hi ESB,
In addition to the suggestion by Jimmy-T, you could go to your local council and ask to speak to someone about the history of the strata plan.
I know, in the case of the City of Sydney Council, folk often call or pony up to the customer service desk asking such queries. The council staff will unearth the original strata plan and can explain to you, whilst holding a copy of the original strata plan, what is common and what is not common property.
The council should also have copies of any by law stipulating the ownership/responsibility/maintenance of the “covering” OR any by law changing the ownership/responsibility/maintenance of the “covering”.