Housing Society Problems & Solutions: Amalgamation of Two Adjacent Flats; Recovery of Maintenance Dues
Often, resident members in cooperative housing societies (CHS) buy flats in new or redeveloped buildings, which adjoin each other and, for habitual convenience, merge them into a single flat (or a duplex flat if situated on separate floors). In most such cases, the owners remain ignorant of the rules that require them to seek explicit permission from the municipal authorities before undertaking construction to merge adjoining flats.
Source: moneylife.in