It’s time for my infamous shoe-box analogy again!
So….. picture a shoe-box that’s been divided into individual compartments. Anything in, on, or in your case leaking through the sides, bottom, or lid of the shoe-box is the responsibility of your Owners Corporation (O/C), and anything in, on, or leaking through any of the compartment dividers is your responsibility.
There are some subtleties in the above analogy, and as water tends to “track” quite extensively from its source, you would be well advised not to do anything yourself just yet, and to instead discuss the matter with your building manager, who by the way is employed to assist you as a member of the O/C, and in the meantime have a read through THIS excellent publication of the NSW Office of Fair Trading.