Section 30(3)(f) in Kerala Municipality Building Rules, 1999
(f)Group E. - Office or business building shall include any building or part of a building having a total floor area of more than 300 sq. metres which is used for transaction of public or private business or for accommodating offices of public or private agencies or for the keeping of records, accounts and similar purposes. Local, State and Central Government office and buildings for office purposes constructed by private sector and quasi government agencies and buildings for the use of defence, court houses, public utility buildings, jails and prisons are included in this group.