“Changes to common property
(1) Procedure for authorising changes to common property An owners corporation or an owner of a lot in a strata scheme may add to the common property, alter the common property or erect a new structure on common property for the purpose of improving or enhancing the common property.
(2) Any such action may be taken by the owners corporation or owner only if a special resolution has first been passed by the owners corporation that specifically authorises the taking of the particular action proposed.”
More here:
https://www.austlii.edu.au/au/legis/nsw/consol_act/ssma2015242/s108.html