I agree with Whale et.al.
However I note that regardless of a special by-law saying that maintenance of a section of common property is the lot owners responsibility, the owners corporations insurance policy will still pay out the claim (I know of several claims where this was the case). Further to this, the lot owners contents will NOT cover any property which is covered by the owners corporations insurance. So in such cases the practical approach is; if the maintenance responsibility lies with the lot owner, then the lot owner arranges the repair and then lodges a claim through the strata insurance company. Any settlement will be automatically less the excess (and GST if applicable) and will be made out to the owners corporation. The owners corporation should then reimburse the lot owner the settlement amount.
If the repair is the responsibility of the owners corporation, then they arrange for the repair, pay the invoice and make the claim.
In this case – sounds like common property to me.