Is there any timeline that a builder must fix the issue by under law? I can see they will just drag their feet until the warranty runs out.
If the problem is identified and established in documents during the warranty period, it doesn’t matter when the warranty runs out.
Out of curiosity, who arranges this? If it is common property, OP shouldn’t have to deal with this and pay out of their own pocket to get this done right?
If it’s common property, the owners corp must pay. If they delay repairs and it’s affecting your lot, you can tell them to fix it or you will. Then make it clear that you will charge them for the costs and if they refuse to pay, you will also make sure they also pay your costs for taking them to the Tribunal to get payment.
Do you have the right to do that? This is what sections 106 (1) and (5) of the Act say:
106 Duty of owners corporation to maintain and repair property
(1) An owners corporation for a strata scheme must properly maintain and keep in a state of good and serviceable repair the common property and any personal property vested in the owners corporation.
(5) An owner of a lot in a strata scheme may recover from the owners corporation, as damages for breach of statutory duty, any reasonably foreseeable loss suffered by the owner as a result of a contravention of this section by the owners corporation.