(2)"occupancy" or "use-group" means the principal occupancy for which a building or a part of a building is used or intended to be used,-and the occupancy classification shall, unless otherwise spelt out in any development plan or any other improvement scheme under any law for the time being in force, include-(a)residential buildings, that is to say, any building in which sleeping accommodation is provided for normal residential purposes with or without cooking facility or dining facility or both, and such building shall include one or two or multi-family dwelling, lodging or rooming houses, hostels, dormitories, apartment houses and flats, and private garages,(b)educational buildings, that is to say, any building used for school, college or day-care purposes involving assembly for instruction, education or recreation incidental to educational use,(c)institutional buildings, that is to say, any building or part thereof ordinarily providing sleeping accommodation for occupants and used for the purposes of medical or other treatment or care of persons suffering from physical or mental illness, disease or infirmity, care of infants, convalescents or aged persons and for penal or correctional detention in which the liberty of the inmates is restricted, and such buildings shall include hospitals, clinics, dispensaries, sanatoria, custodial institutions, and penal institution like jails, prisons, mental hospitals and reformatories,(d)assembly buildings, that is to say, any building or part thereof where groups of people congregate or gather for amusement or recreation or for social, religious, patriotic, civic, travel, sports, and similar other purposes, and such buildings shall include theatres, motion picture houses, drive-in-theatres, city halls, town halls, auditoria, exhibition halls, museums, skating rinks, gymnasia, restaurants, eating-houses, hotels, boarding-houses, places of worship, dance halls, club rooms, gymkhanas, passenger stations and terminals of air, surface and other public transportation services, recreation piers, and stadia,(e)business buildings, that is to say, any building or part thereof used for transaction of business or for the keeping of accounts and records or for similar purposes and such buildings shall include offices, banks, professional establishments, court houses, and libraries for the principal function of transaction of public business and keeping of books and records, and shall also include office buildings (premises) solely or principally used as an office or for office purpose,(f)mercantile buildings, that is to say, any building or part thereof used as shops, stores or markets for display or sale or merchandise, either wholesale or retail, or for office, storage or service facilities incidental to the sale of merchandise and located in the same building, and such building shall include establishments wholly or partly engaged in wholesale trade, manufacturer's whole-sale outlets (including related storage facilities), warehouses, and establishments engaged in truck transport (including truck transport booking agencies),(g)industrial buildings, that is to say, any building or structure or part thereof in which products or materials of all kinds and properties are fabricated, assembled or processed as in assembly plants, and such buildings shall include laboratories, power plants, smoke houses, refineries, gas plants, mills, dairies, factories, workships, automobile repair garages and printing presses,(h)storage buildings, that is to say, any building or part thereof used primarily for the storage or sheltering of goods, wares or merchandise as in warehouse, and such buildings shall include cold storages, freight depots, transit sheds, store houses, public garages, hangars, truck terminals, grain elevators, barns and stables,(i)hazardous buildings, that is to say, any building or part thereof used for the storage, handling, manufacture or processing of highly combustible or explosive materials or products, which are liable to burn with extreme rapidity or which may produce poisonous fumes or explosions during storage, handling, manufacture or processing or which involve highly corrosive, toxic or noxious alkalis, acids or other liquids or chemicals producing flames, fumes, explosions or mixtures of dust or which result in the division of matter into fine particles subject to spontaneous ignition;
