Who’s responsible for new waterproofing when there wasn’t any before?

Our Strata scheme in NSW was registered in 1983 when none of our apartments had bathroom waterproofing and therefore it wasn’t part of common property.

If, however, an owner subsequently renovates their bathroom and is therefore required to install waterproofing under the Building Code, does the new waterproofing automatically become part of common property and Owners Corporation therefore become responsible for its maintenance / repair? 

Or does a bylaw need to be passed specifying who would become responsible for maintenance/repair of the new waterproofing?  

I’m aware that under new NSW Strata legislation waterproofing is common property but I’m not sure if this applies to older buildings in which waterproofing didn’t exist at time of Scheme’s registration.