Unauthorised changes to townhouse courtyard

In our complex, an owner is requesting the EC to approve repairs to buckling tiles in his courtyard. It seems that the courtyard has been repaved at some point, although the Strata Managers can find no evidence of request to do this at all. It does not now resemble other courtyards in their original state. The owner also says that the courtyard was in its current state when he purchased the unit some time ago. What is the responsibility of the OC when unauthorised work has been done, and things go wrong?