newlsie – it all hangs-off the precise wording of that 2010 Special Resolution, where as you’ve stated in summary each Owner could at their discretion and cost enclose their balconies in accordance with some consistent design, and where the Owners Corporation would be responsible for any and all components of those enclosures that were upon completion part of its common property.
So that sounds to me like any Owners of Lots on the top-floor who desire to enclose their balconies would be also required to construct a roof if that’s required to achieve that, with the entire structure being at their expense, and being of that consistent design that you say was approved by your O/C in 2010.
Remember that balcony enclosure is not compulsory, and so any Owners such as those on the top-floor who don’t wish to pay the additional costs of a roof, can simply leave their balconies as they are and await the O/C’s works to re-tile, waterproof, and install new balustrades on those.
If I’ve interpreted everything correctly, then frankly what your O/C agreed to in 2010 as a remedy for the leaking balconies is in my opinion a dog’s breakfast, that’s exacerbated by the fact that the 2-year window that was available for the Registration of a Special By-Law to make Owners responsible for the maintenance of their balcony enclosures has passed.
Again in my opinion, if enclosing balconies is really a cheaper and better solution to the water ingress problem than waterproofing and re-tiling those, then I think that somebody (you?) should put an end to the issue by placing a Motion for Special Resolution by the O/C on the Agenda for the next General Meeting (or to an Extraordinary one if urgent) to have the O/C enclose all balconies, to meet the costs of doing that, and to be responsible for the ongoing maintenance and repair of them where its Common Property is involved – just as it would be under the waterproofing/re-tiling option.
That Motion would need ≥75% of attendees at the Meeting to vote in favour (a “poll vote”) so you and like-minded Owners may need to do a bit of lobbying in advance, but under my suggested solution at least the O/C would be in a position to commission and coordinate the work, and to thereby control both the quality, consistency, and timing/sequence of it which, under the original 2010 scenario, the “general feeling” was it would have been responsible anyway.