ADU rules in State College

The Borough has no accessory dwelling unit use. Chapter XIX lists uses district by district and every residential district is written as 'for the following uses only,' so anything unlisted is prohibited. The one secondary unit the code allows with a house is a 'single apartment unit,' and § 19-501.l(2)(a) requires that it 'shall be contained within the main building,' which rules out a backyard cottage or a converted detached garage. Two other provisions close the door: § 19-501.l(1) bars more than one building for residential use on a lot in the R-1, R-2, R-3H, R-OA and UV districts, and § 19-501.l(5) provides that a detached private garage 'shall not include a dwelling.' The Borough's own Accessory Structures page states the rule plainly: 'Accessory structures are not permitted to be used for dwelling purposes.'

An internal or attached accessory apartment is a by-right listed use. Section 19-501.f permits a 'One-family dwelling with a single apartment unit' in R-1, and every other residential district picks it up by cascade: R-2, R-3H and R-OA permit any use allowed in R-1 or R-2 (§§ 19-601.a, 19-952.a, 19-1152.a), and R-3, R-3A, R-3B, R-4 and R-O build on those (§§ 19-701.a, 19-801.a, 19-901.a, 19-1001.a, 19-1101.b(1)). The apartment must sit inside the main building and hold no more than one bedroom or 500 square feet (§ 19-501.l(2)). Occupancy is capped at two people in the apartment and three unrelated people in the whole building (§ 19-501.l(3)(b)). One trade-off to know about: a house that contains a single apartment loses the right to a home occupation, because § 19-501.l(4) permits home occupations 'in all dwelling units, except one-family dwellings containing a single apartment.'

Section 19-501.l(2)(b) is the whole size rule: 'The apartment unit shall have not more than one bedroom or exceed 500 square feet in total floor area.' There is no percentage-of-house alternative and no separate height standard, because § 19-501.l(2)(a) requires the unit to be contained within the main building, so the house's district bulk, height and lot coverage limits govern the envelope. Occupancy inside the apartment is limited to two people, and the building as a whole to three unrelated people (§ 19-501.l(3)(b)). The Borough's 2024 policy consensus memo for the zoning rewrite calls this 'the current 500 square feet standard' and proposes raising it to 800 square feet, which has not been adopted.

Chapter XIX attaches no owner-occupancy condition to a one-family dwelling with a single apartment unit; the only owner-occupancy language in the zoning code is a floor-area and height bonus for owner-occupied units in the downtown commercial districts (§§ 19-1518.a, 19-1855.a). In practice the Centre Region rental housing permit application the Borough reviews offers both a 'Rental with Owner Occupancy' and a 'Rental without Owner Occupancy' box, so an absentee owner may rent the house and the apartment (each rented unit needs the permit). The exception is short-term renting: § 10-906.c requires the property to be someone's principal place of residence and provides that in a one-family dwelling with an accessory apartment that person 'must live in the one-family dwelling, not the apartment.'

Part H sets parking by use and the residential line reads 'One- and Two-Family Dwellings: 2 spaces for each unit' (§ 19-2403.c). The table has no separate entry for a one-family dwelling with a single apartment unit, so the Zoning Officer applies that per-unit residential standard; confirm the exact count for your lot before you design, since the code is silent on whether the apartment adds two spaces or is absorbed in the house's two. Separately, § 19-501.l(3) allows the permitted number of residents only 'on the condition that adequate off-street parking space is provided on the premises for all vehicles operated or kept by such residents.' Parking must be on the same lot and out of the front yard, though a driveway serving a one- or two-family dwelling may be used (§ 19-2402.b-d). If the apartment is short-term rented, § 10-903 adds one off-street space per bedroom offered, at least 15 feet by 8 feet each.

The single apartment unit is a listed permitted use, not a special exception or a conditional use, so review is administrative with no hearing. A Borough zoning permit is required before erecting or structurally altering a building and before any change of use (§ 19-304.a(1), (2), (4)); the Borough's fee schedule lists $50 for new construction, an addition or a change of use, and applications for one- and two-family dwellings go to the Zoning Officer with roughly 10 business days for initial review. Centre Region Code Administration issues the building permit, and Borough zoning approval is a prerequisite. If the apartment will be rented, the Rental Housing Permit application also goes to the Borough first for a $25 zoning review before CRCA inspects and issues.

Renting the apartment (or the house) requires a Rental Housing Permit: the Borough reviews for zoning compliance and Centre Region Code Administration inspects and issues, and the Borough states the permit is required 'for any unit occupied by anyone other than the owner or the owner's immediate family.' Occupancy caps bind hard in this college town: no more than two people in the apartment and no more than three unrelated people in the building (§ 19-501.l(3)(b)). More than one unrelated student makes the property a Student Home, which needs its own license ($1,000 initial, renewed annually) and, in the R-1, R-2 and R-3 districts, must clear a spacing test (no student home within nine times the district's minimum lot width of another), 1,500 square feet of floor area per dwelling unit and two parking spaces per unit (§ 19-501.l(6)). Short-term rental of under 30 days needs a license under Chapter X, Part I: no more than 120 days per year, proof that the property is the principal residence of the owner or a long-term tenant, one off-street space per bedroom rented, and for a one-family dwelling with an accessory apartment the resident 'must live in the one-family dwelling, not the apartment,' after which the apartment itself may be short-term rented.