conversion of existing single-family detached dwellings into two-family, three- to four-family dwellings or multi-family dwellings is permitted within the Olde Towne, Port Norfolk, and Park View Historic Districts subject to a Use Permit (See Sec. 40.2-533
Read it in the chapter →How this ordinance defines it
The operative definition is the local one. Codes routinely subdivide a category into tiers — “day care 2, family”, “group home 2” — and attach different permissions to each, so only Portsmouth’s own text settles what this covers.