If you haven’t made any changes yourself, then you appear to be talking about a building defect (because that water should drain away) or a blockage of some kind. Either way, it’s the OC’s responsibility to fix it. If the meeting at which you mentioned it was minutes (ie “formal”) then you have given them ample time. I’d do what was suggested to the OP – let them know you are proceeding to NCAT based on their failure to maintain common property. The first step at NCAT is mediation. You may be able to help your performance in mediation by getting a couple of quotes. That way, everyone knows the $$ involved and you’re all mediating over the same amount. Make sure any outcome includes a date by which the repair will be started.