ADU Rules in Philadelphia, PA (2026)
ADU rules, permit requirements, size limits, and fees for Philadelphia, PA. Source-cited from official municipal code.
Yes, ADUs are allowed in Philadelphia, PA.
Philadelphia, PA permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. State and local law governs the approval process. In Philadelphia, the local building department handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in Philadelphia.
ADU Size Limits
ADU Size Limits in Philadelphia: Detached ADU: up to 800 sq ft (max height: varies — see official source). Attached ADU: 800 sq ft. The floor area of an accessory dwelling unit may not exceed 800 sq. ft., except in historic structures (as described in subsection (d)(.1) above).
| Type | Max Size | Max Height |
|---|---|---|
| Detached ADU | 800 sq ft · Verified May 25, 2026 · Source | See official source |
| Attached ADU | 800 sq ft · Verified July 14, 2026 · Source | See official source |
Permit Fees
ADU Permit Fees in Philadelphia: Plan check fee: Varies. Building permit fee: Varies. Impact fees: None. School fees: None or N/A. Total estimated permit cost: Varies.
| Fee Type | Amount |
|---|---|
| Plan Check | $300–$1,200 |
| Building Permit | $500–$3,000 based on construction value |
| Impact Fees | None |
| School Fees | None |
| Total Estimate | See official source |
Permit Timeline
Philadelphia ADU Permit Timeline: Permit timeline has not been confirmed — contact the department for current processing times. Apply through the local building department online permit portal. Contact them through their official website for current contact information.
Setback Requirements
ADU Setback Requirements in Philadelphia: Front setback: Accessory dwelling units are subject to all applicable regulations of the zoning district in which they are located, except as otherwise expressly stated in this section.. Side setback: Accessory dwelling units are subject to all applicable regulations of the zoning district in which they are located, except as otherwise expressly stated in this section.. Rear setback: Accessory dwelling units are subject to all applicable regulations of the zoning district in which they are located, except as otherwise expressly stated in this section.. Accessory dwelling units are subject to all applicable regulations of the zoning district in which they are located, except as otherwise expressly stated in this section.
Parking Requirements
Parking Requirements: Parking requirements have not been confirmed — see official source.
Restrictions & Requirements
- Accessory residential unit must be on same lot as primary dwelling
- Maximum one accessory residential unit per lot in RSA/RSD zones
- ADU must comply with Philadelphia Construction Code (International Residential Code as amended)
- Rear yard minimum 30% of lot depth must remain as open space
- Rowhouse party walls cannot be breached without structural engineering certification
- Historic district properties require Historical Commission review before any exterior changes
- Unit cannot be separately conveyed (sold) apart from primary lot
How Many ADUs Are Allowed?
Number of ADUs Allowed in Philadelphia: Single-family lots: 1. Multifamily properties: Accessory dwelling units are allowed only on lots occupied by a single-family use contained in a detached or semi-detached building in the permitted areas described in § 14-604(11)(d) (Permitted Areas), except within historic structures (as described in subsection (d)(.1) below), where accessory dwelling units are also permitted on lots occupied by a single-family use contained in an attached building.. No more than one accessory dwelling unit is allowed per lot.
- Single-Family Lots
- 1 · Verified May 25, 2026 · Source
- Multifamily Properties
- Accessory dwelling units are allowed only on lots occupied by a single-family use contained in a detached or semi-detached building in the permitted areas described in § 14-604(11)(d) (Permitted Areas), except within historic structures (as described in subsection (d)(.1) below), where accessory dwelling units are also permitted on lots occupied by a single-family use contained in an attached building. · Verified July 14, 2026 · Source
Statewide Preemption
ADU Preemption
We could not confirm a statewide ADU preemption statute for Pennsylvania.
View Pennsylvania preemption detailsFrequently Asked Questions
Can I build an ADU in Philadelphia?
Yes. Philadelphia, PA allows accessory dwelling units. On a single-family lot you can build 1.
How big can an ADU be in Philadelphia?
The maximum size for a detached ADU in Philadelphia is 800 square feet.
How long does it take to get an ADU permit in Philadelphia?
The typical ADU permit timeline in Philadelphia is Philadelphia L&I (Licenses and Inspections) issues permits. Zoning permit first, then building permit. Philadelphia eCLIPSE permit system is online. Typical timeline: 4-8 weeks for zoning approval, 2-4 weeks additional for building permit. Complex projects may require Zoning Board of Adjustment (ZBA) variance.. Total estimated permit fees are $1,000–$5,000 total fees.
Do I need extra parking for an ADU in Philadelphia?
Philadelphia parking rules for ADUs: No minimum parking required for accessory residential units. Philadelphia is a walkable, transit-rich city — L&I does not require additional parking for ADUs. SEPTA rail, subway (Broad Street Line, Market-Frankford Line), and extensive bus network reduce car dependency.
Do I have to live on-site to have an ADU in Philadelphia?
Owner-occupancy requirement in Philadelphia: Owner-occupancy is required. The principal dwelling unit or the accessory dwelling unit must be occupied by the owner of the subject lot.
Source: Philadelphia Code Title 14 (Zoning and Planning) — Accessory Residential Units; Philadelphia Construction Code. Last verified April 6, 2026. View source