Hi Strata Bunny,
I agree with Whale 100%, but would also be seeking any damage caused to personal fixtures & fittings as a result to the defective membrane in the shower recess!
You may need to get an Expert Report (see Sponsors to flat-chat) but NCAT should make an order for the repairs (and damaged fixtures / fittings) to be carried out. Make sure your Expert Report makes note of any ‘lateral transfer’ of water and or ‘capillary action’ that most likely damaged your “internal wardrobe side wall plus the carpet” as neither you nor your tenant are the cause of that damage.
I do not agree with your comment that you are “fully responsible for repairing the damage to the internal wardrobe side wall plus the carpet” which in my opinion is how the problem became apparent… unless you have spider-senses or can see through solid structures (such as the shower base)!!
You never know, your OC may agree at mediation to pay for it all, as they should!!!
Importantly, I think you should submit an application for Mediation (NSW Fair Trading) at the same time you issue your Letter of Demand (Whale’s advice) so that you can get things moving more quickly.
Good luck and I really hope your EC do the right thing by you.