What do you mean by ‘internal common property wall’? If it is an external wall, then I thought you as the owner were responsible for the internal property-facing side of the wall i.e. the internal wall, plaster, membrane etc. that is shared with the brickwork on the outside (which is the OC).
It’s different in Victoria. In NSW and, I believe, Queensland, any surface that backs on to common property or an adjoining lot is common property too. Another example of how Victorian strata law is behind the times.