“Class A” & “Class B” multiple dwellings are defined in Multiple Dwelling Law.
The two types are defined in MDL Sec 4 (Definitions), Items 8 & 9.
“Class A” multiple dwellings include tenements, flat houses, maisonette apartments, apartment houses, apartment hotels, bachelor apartments, studio apartments, duplex apartments, kitchenette apartments, garden-type maisonette dwelling projects and all other except class B. This class is for a permanent residential purpose.
“Class B” multiple dwellings include hotels, lodging houses, rooming houses, boarding houses, boarding schools, furnished room houses, lodgings, clubhouses, college, and school dormitories and dwellings designed as private dwellings but occupied by one or two families with five or more transient boarders, roomers or lodgers in one household.
The two classification as defined in the building code
The building code section 310.1.2 defines “Class A” as a dwelling unit as defined under MDL section 4 and not classified under I-1. “Class A” comes under occupancy group R-2, Whereas “Class B” dwelling unit is categorized under R-1 occupancy group.
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