Allentown, PA Accessory Structures: Garage Conversions (2026)

Under the City of Allentown Zoning Ordinance (eff. Jan. 1, 2026), a garage conversion to habitable space is regulated as an accessory dwelling unit. Section 660-42.C(4) lists the permitted methods of creating an ADU, which include '(d) Converting space within an existing outbuilding on a lot occupied by a single principal dwelling unit to accommodate an accessory dwelling unit.' Outbuildings, defined in Section 660-49.B, expressly include detached garages and carports. A garage-conversion ADU must satisfy all Section 660-42 requirements: it must be on a lot with a single principal dwelling unit (Sec. 660-42.C(1)(a)); a detached-ADU lot must have alley or street access at the rear or street side (Sec. 660-42.C(1)(c)); no more than one ADU per lot (Sec. 660-42.C(3)); floor area may not exceed 800 sq ft or 40% of the principal dwelling, whichever is less (Sec. 660-42.C(5)); at least one additional off-street parking space is required (Sec. 660-42.C(7)); the outbuilding must be on a permanent foundation (Sec. 660-42.C(8)(a)); plans must be reviewed and approved by the building official for compliance with all building and life-safety codes before a building permit issues (Sec. 660-42.C(9)); and the owner-occupancy, short-term-rental, and deed-restriction conditions of Sec. 660-42.C(10)-(12) apply. The City's residential permit guidance separately confirms that 'finishing a basement, attic or garage' and any 'change of use or occupancy' require a building permit. Converting a garage that is not part of an ADU into other living space (e.g., a family room) is a structural alteration / change of use and likewise requires permits.