ADU laws in Pennsylvania

In plain words

Pennsylvania does not have a statewide ADU law. An accessory dwelling unit (ADU) is a small second home on the same lot as a house. It might be a basement apartment, a unit over a garage, or a backyard cottage. Today each city, borough and township decides through its zoning. Zoning means the local rules about what you can build where. Some towns allow ADUs, often with limits. Limits you may see include a rule that the owner live on site, that only family members live in the unit, or that you add a parking space. Other towns do not allow ADUs at all, or make you go through a public hearing first. Pittsburgh allows them only in one small pilot area for now, though the city is weighing a citywide change. That may change soon. In June 2026 the state House passed HB 2186 by a vote of 139 to 62. It would let you build one ADU per lot 'by right'. That means the town must allow it, with no hearing, if you meet the basic rules. A Senate bill, SB 1346, would do something similar but would skip Philadelphia and Pittsburgh. Neither bill is law. A bill must pass both chambers by November 30, 2026, and then be signed by the Governor. If not, it dies and must start over. Until then, your local rules decide. You may be able to build one if your local rules and your property allow it.

The rules at a glance

What to do next

1. Call your municipal zoning officer (city, borough or township) and ask whether ADUs, in-law suites or accessory apartments are permitted in your zone, and by what process.
2. Ask whether approval is a simple zoning permit or needs a special exception, conditional use or variance hearing, and what it costs.
3. Write down local rules on owner occupancy, who may live in the unit, size, height, setbacks and parking before you design.
4. Check HOA covenants and your deed; the pending bills would not override private restrictions.
5. If your town does not allow ADUs, follow HB 2186 and SB 1346 on palegis.us; the session ends November 30, 2026.
6. Plan for building permits under the statewide Uniform Construction Code, including septic or sewer capacity if the ADU adds a bathroom.

What your town still decides

The Municipalities Planning Code (MPC) lets each city, borough and township in Pennsylvania write its own zoning. Nothing in the MPC requires them to allow ADUs, so the answer depends on the town; some rural townships have no zoning at all, while building permits everywhere follow the statewide Uniform Construction Code. The MPC does not cover Philadelphia (a first class city) or Pittsburgh (a second class city), which zone under their own laws. That is why the pending Senate bill, an MPC amendment, would not reach those two cities, while the House-passed bill, a new chapter in Title 53, would cover every municipality with zoning. The pending bills would ban owner-occupancy rules, family-relationship rules, extra parking demands and large setbacks, a sign that lawmakers see these limits in local codes today. Where a town does not list ADUs as permitted, owners usually need a special exception, conditional use or variance, each of which involves a public hearing.

Examples of local rules

• Pittsburgh: Ordinance 32 of 2018 (Council file 2018-0558, passed September 4, 2018) created an interim Accessory Dwelling Unit Overlay District, Zoning Code section 912.08, set to last 24 months unless made permanent. The city says it was mapped over the single-family parts of the Garfield neighborhood, so ADUs are not allowed citywide. Inside the overlay: one ADU per lot, under 800 sq ft, owner must live on site, no leases under 30 days, no taller than two stories or 30 feet, no on-site parking required, exempt from minimum lot size, and a recorded deed restriction. Council Bill 2025-1545 would allow ADUs by right citywide, along with parking and affordable housing changes; the Planning Commission recommended it in June 2026 and Council held a public hearing on September 23, 2026, but it was still held in Council with no final vote as of this check. Source
• Philadelphia: Philadelphia zones under its own code, not the Municipalities Planning Code. A 2022 law-firm summary says ADUs were allowed by right only in a few zoning districts (RSA-5 and CMX-1), up to 800 sq ft, inside the main building or an existing accessory building, with the owner living on the property. A 2021 Council bill to allow ADUs more widely was amended to exclude several council districts. These details come from secondary sources; confirm current rules with the city's Department of Planning and Development or Department of Licenses and Inspections. Source

What we’re still confirming

• The House passed a statewide ADU bill (HB 2186); whether the Senate acts on it or on its own bill, SB 1346, before the session ends November 30, 2026 is open.
• Whether Pittsburgh made its 2018 ADU overlay permanent, and whether City Council will pass Bill 2025-1545 to allow ADUs citywide by right, isn't confirmed.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.