Bathroom tiles coming off – common property?

Hi Amanda et al,

We have an apartment in our self-managed building where the tiles are starting to come off the bathroom walls.

Details are:
Building is c. 20 years old. Tiles are original, on internal plasterboard walls (i.e. not lot boundary walls). According to builders, they’re coming off due to expansion/contraction of substrate (with no relief joints).

My question is whether they’re an owners corporation or lot owner responsibility to repair.

Is this a simple question or are there other factors that affect it?

Thanks,

David