Do I Need a Permit to Build an ADU in Philadelphia, PA?

ADU-specific overview

What makes this different from a simple accessory structure

Pulled from the city's ADU guidance and linked code references.

Permit type: Residential building permit through the Philadelphia Department of Licenses and Inspections (L&I), submitted via the eCLIPSE online portal. Both attached ADUs and new detached ADU structures require a full building permit under the Pennsylvania Uniform Construction Code (PA UCC). A zoning permit application is submitted concurrently to confirm dimensional compliance.
Maximum size: Philadelphia's Zoning Code does not specify a single universal ADU square footage cap; size is governed by the applicable district's lot coverage, setback, and open space requirements. In RSA-5 districts, typical lot and setback constraints effectively limit most detached ADUs to the usable rear-yard footprint. Verify maximum buildable area against the specific district standards using Philadelphia Atlas.
Setbacks: ADUs must comply with the setback standards of the applicable zoning district. RSA-5 and CMX-1 districts typically have rear and side setback requirements that the ADU must satisfy. A Certificate of Appropriateness from the Philadelphia Historical Commission is required if the property is in a historic district. Use Philadelphia Atlas to identify the specific setback requirements before designing.
Owner occupancy: Not required. Philadelphia's ADU ordinance does not impose an owner-occupancy condition — the property owner is not required to live in the principal dwelling or the ADU. This distinguishes Philadelphia from cities that still enforce owner-occupancy requirements.
Parking: Philadelphia's ADU zoning does not impose a separate off-street parking requirement for the ADU unit. However, the underlying zoning district's general parking requirements still apply to the lot. Confirm whether the primary dwelling's parking configuration is affected by the ADU design with L&I or an attorney familiar with the Philadelphia Zoning Code.
Utilities: Water, sewer, gas, and electrical service connections must be reviewed as part of the L&I permit process. Depending on the ADU layout, a separate meter or service entry may be required. The Philadelphia Water Department and PECO each have independent review processes for new connections that should be coordinated in parallel with the L&I permit.
JADU distinction: Pennsylvania and Philadelphia do not use a California-style Junior ADU (JADU) designation. Interior conversions of space within the primary dwelling are treated as attached ADUs and follow the same L&I permit and zoning compliance path as other ADU types.

Pennsylvania does not have a statewide ADU preemption law comparable to California SB 897, Washington HB 1337, Oregon HB 2001, or Colorado HB24-1152. Philadelphia's 2021 ADU amendments are a city-level zoning change, not a state mandate — so the eligible zones (RSA-5, CMX-1) and standards are specific to Philadelphia and can change with further code amendments.
Philadelphia's 2021 Zoning Code amendments added by-right ADU allowances in RSA-5 and CMX-1 districts. Properties in other zoning districts may still require a variance from the Zoning Board of Adjustment (ZBA). Check Philadelphia Atlas to confirm the applicable zoning district before beginning the design process.
Philadelphia Historical Commission review applies to ADUs visible from the public way or otherwise within the commission's jurisdiction in designated historic districts, including Society Hill, Rittenhouse-Fitler, and other local or national register districts. Engage the Historical Commission early if your property is in a historic area — their review timeline is independent of L&I plan review.

Fees

Estimated city fees

Baseline for a simple permitted adu: $550–$1,600+ estimated combined L&I permit and plan review fees for a typical Philadelphia ADU; trade permits, ZBA variance proceedings, and historic review costs are additional

Fee	Amount	Notes
Building permit fee (valuation-based)	$400–$1,200+ (estimated range)	Philadelphia L&I building permit fees are based on declared project valuation. ADU construction — whether a detached structure, addition, or interior conversion — generates higher permit fees than a small shed permit. Verify current fee schedules at eclipse.phila.gov before budgeting.
Plan review fee	$150–$400 (estimated)	A plan review fee is assessed separately from the building permit fee. Combined permit and plan review for a new ADU commonly runs $550–$1,600 depending on scope and valuation.
Pennsylvania state surcharge	$10–$30	Pennsylvania assesses a state surcharge on all permitted residential construction projects, collected by L&I at permit issuance and remitted to the Commonwealth under the PA UCC.
Trade permits (electrical, plumbing, mechanical)	$200–$1,200+ each depending on scope	Separate trade permits and inspections are required for a habitable ADU with full utilities. Each trade permit carries its own L&I review fee.
Zoning variance or ZBA hearing (if required)	Varies; hearings typically add $500–$2,000+ in time and filing costs	By-right ADUs in RSA-5 and CMX-1 do not require a variance. If your zoning district does not allow ADUs by right or the design exceeds dimensional limits, a Zoning Board of Adjustment (ZBA) hearing is required before L&I can accept a permit application.
Philadelphia Historical Commission review (if applicable)	Varies by project scope	Properties in Philadelphia historic districts (including Rittenhouse-Fitler Historic District, Society Hill Historic District, and other local or national register districts) may require a Certificate of Appropriateness from the Philadelphia Historical Commission before L&I will process the building permit.

Documents

Required documents

Building permit application submitted through the L&I eCLIPSE online portal at eclipse.phila.gov.
Zoning permit application or zoning compliance documentation confirming the ADU is allowed by-right in the applicable zoning district and that the design meets Philadelphia Zoning Code dimensional standards for the district.
Scaled site plan showing lot lines, the principal dwelling, the proposed ADU footprint, setback dimensions from all lot lines, driveway/access layout, and lot coverage calculation.
Construction drawings including floor plans, elevations, cross sections, and roof plan for the ADU, sized and detailed to comply with the Pennsylvania Uniform Construction Code (PA UCC / 2018 IRC with PA amendments).
Structural footing and framing details showing footing depth below the Philadelphia frost line (minimum 36 inches), post/beam/joist sizing, ledger connection details for attached ADUs, and all connection hardware.
Utility plans showing proposed water, sewer, gas, and electrical service connections, meter locations, and any new service entry points.
Pennsylvania Home Improvement Contractor (HICPA) registration number for the contractor performing the work, or a signed homeowner-builder certification if the owner is self-contracting under PA UCC owner-occupant provisions.
Certificate of Appropriateness from the Philadelphia Historical Commission if the property is in a designated historic district and the ADU work is subject to their review.

Timeline

Typical timing

Plan review: 10–20 business days for standard residential plan review through eCLIPSE
Total cycle: 3–7 months from initial design to final inspection for a typical Philadelphia ADU

ZBA variance proceedings (if the district does not allow ADUs by-right) can add 3–5 months before the permit application is accepted. Philadelphia Historical Commission review adds additional time if applicable. Straightforward by-right RSA-5 ADUs with complete submissions typically move faster than the outer bound.

Process

How the permit process works

Confirm ADU eligibility for your zoning district Use Philadelphia Atlas (atlas.phila.gov) to identify your parcel's zoning district. ADUs are allowed by-right in RSA-5 and CMX-1 districts under the 2021 amendments to the Philadelphia Zoning Code. If your district is not RSA-5 or CMX-1, confirm whether ADUs are permitted in your zone before investing in permit drawings — a ZBA variance may be required.
Check for historic district and other overlay conditions Determine whether the property is in a Philadelphia historic district subject to review by the Philadelphia Historical Commission. Historic review must be completed and a Certificate of Appropriateness obtained before L&I will process the building permit. Also check for floodplain, special review overlay, or HOA/deed-restriction conditions that may apply independently of city zoning.
Design the ADU to comply with PA UCC and zoning dimensional standards Prepare the ADU design against the dimensional standards of the applicable zoning district (lot coverage, setbacks, height, open space) and the structural and life-safety requirements of the PA UCC. Philadelphia's frost line is 36 inches — footing depth is a common correction item on residential submissions. Engage a licensed design professional or contractor familiar with L&I submissions early.
Plan utility connections with Philadelphia Water Department and PECO Confirm water, sewer, and electrical service strategy before finalizing the permit application. Depending on the ADU configuration, a separate service lateral or meter may be required. The Philadelphia Water Department and PECO may have their own review and connection requirements that run independently of the L&I permit.
Submit zoning and building permit applications through eCLIPSE Create an eCLIPSE account at eclipse.phila.gov and submit both the zoning permit application and the building permit application with all supporting documents: site plan, construction drawings, structural details, utility plan, and contractor HICPA information or owner-builder certification. L&I processes all Philadelphia residential building permits through eCLIPSE.
Respond to zoning and plan review comments L&I zoning reviewers will check the design against Philadelphia Zoning Code dimensional standards. Plan reviewers will check the drawings for PA UCC structural and life-safety compliance. Address any correction notices and resubmit through eCLIPSE. Track review status through the portal.
Pay fees, obtain trade permits, and begin construction Once plan review approvals are issued, pay the permit fee, plan review fee, and PA state surcharge through eCLIPSE. Pull separate trade permits for electrical, plumbing, and mechanical work. Post the building permit card on site before starting any construction. Keep approved drawings on site throughout.
Schedule L&I inspections and close out the permit Schedule the required L&I inspections through eCLIPSE: footing (before concrete pour), framing, utilities (rough-in), and final inspection. After passing the final inspection, L&I closes the permit. The ADU may not be lawfully occupied before the final inspection is passed and the permit is closed.

Code basis

What Philadelphia reviews against

Philadelphia Zoning Code (2022 edition with 2021 ADU amendments, Chapter 14 of the Philadelphia Code) for land-use allowances and dimensional standards; Pennsylvania Uniform Construction Code (PA UCC), based on the 2018 International Residential Code (IRC) with Pennsylvania amendments, enforced by the Philadelphia Department of Licenses and Inspections (L&I).

Residential permit page Philadelphia permit portal

If you skip the permit

What can go wrong

Philadelphia L&I can issue a stop-work order requiring all work to cease immediately and post a violation notice on the property.
L&I can require removal or demolition of unpermitted ADU work at the owner's expense; after-the-fact permitting may require opening concealed construction for inspection.
Pennsylvania law requires sellers to disclose known code violations and unpermitted work in residential transactions — an unpermitted ADU creates material disclosure obligations that can affect sale price, complicate financing, or require remediation before closing.
An unpermitted ADU in a Philadelphia historic district may trigger separate enforcement by the Philadelphia Historical Commission in addition to L&I enforcement.
A non-permitted ADU cannot lawfully be occupied or rented; it lacks a final L&I inspection and closed permit.
Lenders and title companies increasingly flag unpermitted additions in Philadelphia transactions, creating complications at refinancing or home equity applications.