ADU Rules in Pittsburgh, Pennsylvania

Pittsburgh is Pennsylvania's Second Class City and the seat of Allegheny County, situated dramatically at the confluence of the Allegheny, Monongahela, and Ohio Rivers — a point known as the Golden Triangle (Point State Park). With approximately 300,000 residents and a legacy of steel-era neighborhoods cascading down steep hillsides, Pittsburgh presents a unique context for accessory dwelling unit development.

No Pennsylvania Statewide ADU Law

Pennsylvania has not enacted statewide ADU preemption legislation. The Pennsylvania Municipalities Planning Code (MPC) governs how municipalities structure their zoning, but local content — including ADU rules — is entirely determined by Pittsburgh's own Zoning Code.

Pittsburgh Zoning Code Framework

Pittsburgh's Zoning Code divides residential land into several district types:

• R1A and R1B (Single-Unit Residential): Lower-density districts where accessory structures are generally permitted but accessory dwelling units may require additional review.
• R2 (Two-Unit Residential): Allows two-unit structures as of right, which may include configurations equivalent to ADUs.
• RM (Multi-Unit Residential) and RIV (Riverfront): Allow higher-density uses.
• UI (Urban Industrial) and mixed-use districts in revitalizing areas may permit accessory dwelling arrangements.

Accessory structures (including potential ADU conversions) in single-unit districts are generally subordinate uses. Pittsburgh's zoning has provisions for accessory buildings in rear yards; whether a converted accessory structure can be a habitable dwelling unit depends on the district's specific regulations.

Topography and Steep Slope Overlays

Pittsburgh's terrain is one of its defining characteristics — and one of its greatest development constraints. The city's Steep Slope Overlay District applies to areas with slopes of 15% or greater. Key requirements include:

• Geotechnical (soils) report may be required.
• Limitations on impervious surface coverage.
• Enhanced stormwater management design.
• Retaining wall engineering may be needed.

Many of Pittsburgh's most historically interesting hillside neighborhoods (Mount Washington, Duquesne Heights, Troy Hill, Perry North) fall within steep slope areas. ADU construction in these locations requires careful site assessment.

Historic Districts and Design Review

Pittsburgh has numerous historic districts and locally designated neighborhoods (Lawrenceville, Mexican War Streets, Allegheny West, Shadyside). Work on properties in historic districts requires review by the Pittsburgh Historic Review Commission. Exterior alterations and new accessory structures must receive a Certificate of Appropriateness.

Urban Infill and ADU Policy Context

Pittsburgh has actively promoted urban infill development to address population loss and housing affordability. The Pittsburgh Department of City Planning has engaged in planning efforts that acknowledge accessory dwelling units as a housing strategy. Verify current policy positions and any recent ordinance updates directly with the Department of City Planning.

Permit Process

1. Zoning review: Department of City Planning, 200 Ross Street. Determine if your ADU is permitted as-of-right or requires a variance/special exception.
2. Building permit: Bureau of Building Inspection (BBI), 200 Ross Street. Required for all new construction and structural alterations.
3. Zoning Board of Adjustment: Appeal body for variances; meets regularly; filing fees apply.

Contact

• Bureau of Building Inspection: (412) 255-2175
• Department of City Planning: (412) 255-2200, pittsburghpa.gov/dcp
• Zoning Board of Adjustment: (412) 255-2126

Disclaimer: Zoning regulations change frequently. Verify all information directly with the Pittsburgh Department of City Planning and Bureau of Building Inspection before making any development decisions.