encrochment of common area by flat owner

If the apartment owners have a society, inform them in writing and request for removal of encroachments, if they remain silent issue a notice to such encroachers to remove such constructions and then contact advocate for permanent remedy.

Please mention (1) in which State your So ciety is,(2) whether the Society is registered and if so, (3)under which Act the Society is registered. Law are different from State to State and also for Act under which it is registered.

If no registered Society has been formed who is the owner of the common area?  It will be difficult to take action. Form a society and register it. You have to go to court.