ADU rules in Baltimore, MD — also called accessory dwelling unit regulations or granny flat ordinances — cover setbacks, owner-occupancy, parking, and permit requirements.
Baltimore's Article 32 Zoning Code does not have a general 'ADU' use, but Section 15-504 allows existing carriage houses in any Residential or OR District to be converted into a single-family detached dwelling, treated as an accessory structure on the same lot.
Article 32 (TransForm Baltimore, effective 2017) regulates accessory structures and uses in Title 15, Subtitle 5. Section 15-501 establishes general standards: an accessory structure must be on the same lot as the principal structure, may not occupy more than 50% of a required rear yard, may not exceed 15 feet in height, and may not be erected before construction of the principal building. Section 15-504 is the carriage-house provision: a pre-existing carriage house in a Residential District or OR District may be converted to a single-family detached dwelling if the building contains at least 350 square feet of gross floor area, and the conversion may not enlarge the building height or footprint by more than 20%. Maryland's Accessory Dwelling Units Act of 2025 (SB 891 / HB 1466), effective October 1, 2025, requires Baltimore City and charter counties to adopt local ADU authorizing legislation by October 1, 2026, which is expected to expand by-right ADU options beyond the carriage-house pathway.
Building or converting a structure to a dwelling without permits and zoning approval is a Code violation enforced by the Department of Housing and Community Development; violators face stop-work orders, citations, and the requirement to remove or restore unpermitted work. Carriage-house conversions exceeding the 20% size or height expansion limit lose the Section 15-504 allowance.
Baltimore, MD
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Baltimore, MD
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Baltimore, MD
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Baltimore, MD
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Baltimore, MD
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