Millcreek, PA Accessory Structures: ADU Owner Occupancy (2026)

Millcreek Township Code § 145-58 sets the supplemental criteria for an In-Law Apartment in the Township's Zoning Ordinance. Subsection B is the owner-occupancy rule. The Dwelling in which the In-Law Apartment is being created must be owner-occupied, and the Dwelling Unit occupied by the owner must be greater than 70% of the total living space, including the In-Law Apartment. The apartment's living space cannot exceed 720 square feet or 40% of the principal Dwelling's total area, whichever is less.

The two measurements use different bases. "Living space" includes the Dwelling's area excluding that of any garage, while "total area" includes the garage and all other portions of the Dwelling. Subsection A adds that the use must at all times meet all elements of the definition in Article II and every criterion and condition imposed, so owner occupancy is a continuing condition and not a one-time test at approval.

The same section limits the unit in other ways. Only one In-Law Apartment is allowed within any Single-Family Dwelling, Detached (subsection C). No more than two bedrooms are permitted (D). The apartment can be located only within a primary Dwelling (E), which rules out a detached garage unit or a separate cottage. Any addition or modification made to accommodate it must be architecturally integrated with the principal Dwelling's use as a Single-Family Detached Dwelling (F), and the work must meet the Pennsylvania Construction Code regulations (G).

The district use lists in Chapter 145 place the In-Law Apartment among the Accessory Uses permitted by Conditional Use in the CR Conservation Residential, R1 Single-Family Residential and R2 Low-Density Residential Districts. In those districts the Board of Supervisors approves it, after finding that the general criteria in Article IV and the criteria in Article V are satisfied. Section 145-107 also requires a Zoning Permit from the Zoning Officer before a change in use or occupancy of a Building.