ADU Rules in Baltimore City, Maryland

Baltimore is Maryland's largest city and an independent city — it has been legally separate from Baltimore County since 1851 and is not part of any county. With a population of about 585,000 (the largest independent city in the US by population), Baltimore is a major mid-Atlantic urban center with a diverse housing stock ranging from historic rowhouses to modern apartments. The city has been expanding ADU allowances to address housing affordability. Baltimore County (with its seat in Towson) is an entirely separate jurisdiction.

Baltimore vs. Baltimore County

• Baltimore City: Independent city with its own Zoning Code — use Baltimore City's permit process
• Baltimore County: Separate county government based in Towson — completely different jurisdiction
• Do not confuse the two: permits from one are not valid in the other

Baltimore City Zoning Code

The Baltimore City Zoning Code governs all land use within Baltimore City limits. Baltimore has historically had a significant stock of rowhouses, and the city has been working to make it easier to create accessory dwelling units — including carriage houses and basement apartments — as part of its housing strategy.

Permitted ADU Types

Per Baltimore City Zoning Code (subject to verification):

• Detached ADUs: Carriage houses and rear-yard structures in eligible zones
• Attached ADUs: Additions to rowhouses and other structures
• Interior conversions: Basement and upper-floor conversions with separate entrance
• Garage conversions: Converting existing garage to ADU

Baltimore's rowhouse typology creates particular opportunities for basement ADUs and carriage house conversions in rear alleys.

Size Limits

Per Baltimore City Zoning Code (verify current standards):

• Maximum floor area per zone
• Lot coverage restrictions apply

Setbacks

Per Baltimore City Zoning Code:

• Rear: Minimum setback (rowhouse alleys create unique situations)
• Side: Minimum setback

Maryland ADU Rules

ADU rules in Maryland are set by each county and municipality. Verify current ADU requirements with the Baltimore City Department of Planning.

Chesapeake Bay Critical Area

Properties within 1,000 feet of tidal waters, tidal wetlands, and tributary streams of the Chesapeake Bay are subject to Maryland's Critical Area Law. Baltimore's waterfront neighborhoods (Inner Harbor, Fells Point, Locust Point, Canton, etc.) may be in the Critical Area — verify status for waterfront properties.

Historic Districts

Baltimore has numerous historic districts including:

• Fells Point: Historic district and National Register area
• Federal Hill: Historic district
• Bolton Hill, Mount Vernon, and others

Properties in historic districts require review by Baltimore's Commission for Historical and Architectural Preservation (CHAP).

100-Year Floodplains

Parts of Baltimore near the waterfront, Jones Falls, and other waterways may be in FEMA flood zones. Verify flood map status.

Permit Process

1. Verify zoning: Baltimore City Department of Planning (baltimorecity.gov)
2. Check Critical Area status: If near the Inner Harbor or tidal waterways
3. CHAP review: If in a historic district
4. Check flood zone: If near waterways
5. Submit plans: Baltimore City Permit Application Center
6. Building permit and inspections
7. CO: Required before occupancy

Contact

Baltimore City Department of Planning 417 E. Fayette Street, Baltimore, MD 21202 Phone: (410) 396-7526 Website: planning.baltimorecity.gov

Baltimore City Permit Application Center 469 City Hall, 100 N. Holliday Street, Baltimore, MD 21202 Phone: (410) 396-3360

Disclaimer: Baltimore City and Baltimore County are separate jurisdictions. ADU rules are evolving following Maryland's 2024 statewide ADU legislation. Verify current standards with Baltimore City before starting any project.