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ADU rules in Pennsylvania

Representative cities: Philadelphia, Pittsburgh.

Verify locally. Pennsylvania's UCC is administered locally — over 90% of municipalities enforce it themselves, so permit thresholds and fees vary by city or township. Always verify with your local building department (e.g., Philadelphia L&I). ADU rules below are drawn from official sources — always confirm with the issuing building department before designing or building.

ADU permit rule

Permit requiredCase by casecity authority
Fee basis
Permit fees set by each municipality; Philadelphia adds a $3 city and $4.50 state surcharge per permit plus plan-review fees. No single statewide fee.
Typical timeline
Typically ~15 business days for residential alterations (Philadelphia L&I); other PA municipalities vary.
Setback
—
Area threshold
Not size-exempt
Exempt if
Not exempt
Go / no-go
case-by-case
ADUs require a building permit plus zoning/use approval. The PA UCC governs construction; local zoning controls whether an ADU is allowed on your lot. Verify with your municipality (e.g., Philadelphia L&I).
ADU official sources: City of Philadelphia — Get a Building Permit · PA Dept. of Labor & Industry — Uniform Construction Code (UCC)
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Frequently asked questions

Do I need a permit to build an ADU in Pennsylvania?

Per Pennsylvania rules, an ADU is "yes" for a permit and the authority is "city". ADUs require a building permit plus zoning/use approval. The PA UCC governs construction; local zoning controls whether an ADU is allowed on your lot. Verify with your municipality (e.g., Philadelphia L&I). Always confirm with the issuing building department.

How big can an ADU be in Pennsylvania?

Size limits for an ADU in Pennsylvania are set by local zoning — verify with your city building department.

What are the ADU setbacks in Pennsylvania?

Setback rules vary by city in Pennsylvania; confirm with the local planning or building department.

How much does an ADU permit cost in Pennsylvania?

Fee basis: Permit fees set by each municipality; Philadelphia adds a $3 city and $4.50 state surcharge per permit plus plan-review fees. No single statewide fee.

State-wide sources: PA Dept. of Labor & Industry — Uniform Construction Code (UCC) · PA UCC Adopted I-Codes (AWC Code Adoption Map) · City of Philadelphia — Get a Building Permit · City of Philadelphia — EZ Permits (no plans)

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