sassa – your problem is quite complex as it appears that neither your Owners Corporation (O/C) nor you has as yet accurately determined the means by which water enters the unit below.
In my opinion it’s not the source/s of the leakage that are the problem in this case, but moreso the means by which water then enters the common property and/or the unit/s below – it’s quite possible that you could spend money replacing the damp-course or otherwise sealing the space between your balcony door and the concrete slab below and yet still not resolve the water ingress problems.
You’d be surprised by just how far water can “track” from a source or sources of leakage before it eventually emerges – in this case through the ceiling of the unit below yours.
It appears however that whatever the source/s of the leakage (balcony door, roof, or ??), water is passing through the concrete slab that forms the common floor of your unit and the ceiling of the unit below, and as that slab is common property, its your O/C who should be investigating and effecting the necessary repairs to it if it’s confirmed as the means by which water is permitted to enter the common property and the unit/s below.
That’s not to say that you should do nothing if your O/C’s investigations do confirm that water is passing through its concrete slab and that’s corrected, because at least some of that water is “available” because it can penetrate the damp-course below your balcony door, and you’re responsible for meeting the cost of rectifying that source of ingress – if only because it could also affect your Unit and/or your balcony door.
So as a specific response to your questions:
Q: what rights do I have when someone is insisting that I repair something and we do not know 100% what the cause is?
A: If you’re referring to your downstairs neighbour, you are are both part of the O/C and it, as a collective, should be arranging and paying for whatever investigations are necessary to determine the means by which water is entering the Unit below, and IF it’s proven to be the concrete slab then the O/C should meet to costs of repairs to that. So your “right” is to do nothing until your O/C investigates and determines the cause.
Q: The strata has paid for the damage of unit below where the dampness was, so basically they will not pay for the cause but will repair below is this fair.
A: Your O/C acted improperly – it should have investigated, determined the means by which the water entered the unit below, rectified the problem and any damage that it may have caused to the unit below in the process having those works undertaken (e.g. to the unit’s ceiling), and left the rectification of any damage that the leakage itself caused to the Owner below or to his contents insurance.
and…. with regard to the question in your subsequent post:
Q: If windows repaired by owner as building prior to 1974 what happens if a future by law is added to include repairs of windows under strata. Does the owner get compensated for having had to change their windows due to water leakages?
A: Probably not, unless you can successfully argue that provision as an amendment to the proposed Special By-Law when it’s put to your O/C at a General Meeting, and your O/C required or otherwise “encouraged” you to make the repairs.