Philadelphia's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Philadelphia, Pennsylvania, there are 4 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

ADU Owner Occupancy

An accessory dwelling unit or the main house must stay owner-occupied, locked in by a recorded deed restriction before final occupancy.

Key details: Governing section: Philadelphia Code § 14-604(11)(e). Requirement: Owner must occupy principal or ADU. Mechanism: Recorded affidavit + deed restriction. Removal: Requires Zoning Board approval. Units per lot: One ADU maximum.

Occupying neither unit as owner, or removing the recorded deed restriction without Zoning Board approval, puts the ADU out of compliance and can block final occupancy sign-off or trigger enforcement by the Department of Licenses and Inspections.

Shed & Carport Rules

Philadelphia exempts a small shed from permits only when it is 120 sq. ft. or less, no taller than 15 ft. (one story), located in the rear yard, and accessory to a one- or two-family dwelling - per L&I Permit Guide PG_011 and the Zoning Code. A shed in a front or side yard, or larger than 120 sq. ft., requires a zoning permit, and a shed over 200 sq. ft. requires both a zoning and a building permit.

Key details: Code Section: Phila. L&I Permit Guide PG_011; Zoning Code Sec. 14-604(2). Permit-Free Size: 120 sq. ft. or less, in rear yard, one- or two-family dwelling. Height Limit: Not more than 15 ft. and not more than one story. Zoning Permit Needed: Front/side yard placement, or shed over 120 sq. ft.. Building Permit Needed: Sheds over 200 sq. ft..

Building a shed that exceeds Zoning Code size limits, or placing one in a front/side yard without the required zoning permit, draws a refusal or violation notice from the Department of Licenses and Inspections; correcting it requires either removal or a Zoning Board of Adjustment appeal (community meeting plus public hearing). Additional electrical, mechanical, or plumbing permits may also be required.

ADU Rules

Philadelphia permits accessory dwelling units (ADUs) only on lots in the RSA-5 or CMX-1 base zoning districts (and certain overlay districts), under Zoning Code Section 14-604(11). The ADU must be inside the principal building or inside a detached accessory building (such as a detached garage) that already existed as of the Code's effective date, be no larger than 800 square feet, be limited to one per lot, and the owner must occupy either the principal or accessory unit.

Key details: Code Section: Philadelphia Zoning Code Sec. 14-604(11). Permitted Districts: RSA-5 or CMX-1 base district (plus qualifying overlays). Max Floor Area: 800 sq. ft. (more allowed only in qualifying historic structures). Location: Inside principal building or pre-existing detached accessory building (e.g. detached garage). Owner Occupancy: Required; affidavit + deed restriction recorded before occupancy.

Creating or occupying an ADU without a zoning/use registration permit, or in a district where it is not permitted, is a Zoning Code violation enforced by the Department of Licenses and Inspections; a refusal triggers an appeal to the Zoning Board of Adjustment requiring a community meeting and public hearing. Failure to record the required owner-occupancy affidavit and deed restriction blocks final occupancy approval.

This is not one of those rules that cities tend to ignore. Philadelphia actively enforces its adu rules requirements.

Garage Conversions

Philadelphia does not have a standalone garage-conversion ordinance, but a detached garage is the prime candidate for an accessory dwelling unit under Zoning Code Section 14-604(11): an ADU may be located inside a detached accessory building such as a detached garage that already existed as of the Code's effective date, in the RSA-5 or CMX-1 districts, up to 800 sq. ft., owner-occupied. Converting a garage to any new use is a change of use requiring a use registration permit.

Key details: Code Section: Phila. Zoning Code Sec. 14-604(11); Admin. Code A-301.1.5. Eligible Building: Detached garage in existence as of the Zoning Code effective date. Allowed Use: ADU up to 800 sq. ft. in RSA-5 / CMX-1; or other permitted accessory use. Permit: Use registration permit required for the new use (A-301.1.5).

Converting a garage to living space or another use without the required zoning and use registration permits is a Licenses and Inspections violation; an illegal dwelling unit can be ordered vacated and the work undone. If the proposed conversion exceeds what the Zoning Code allows, L&I issues a refusal and the owner must seek a variance from the Zoning Board of Adjustment.

The Bottom Line

Philadelphia's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Philadelphia is broadly strict or permissive.

This guide is based on Philadelphia's current municipal code. Local rules can and do change, so check the individual ordinance pages for the latest details, penalties, and FAQs.