5 rules for unincorporated Baltimore County, Maryland.
Verified from official government sources
Baltimore County allows an accessory apartment as a temporary use in an owner-occupied single-family home or accessory building. It requires a Use Permit, must house only family members, cannot have separate meters, and must be renewed every two years.
BCZR § 400.4 (Accessory Apartment)
The size of the accessory apartment may not exceed one third of the overall floor area of the dwelling or 2,000 square feet, whichever is less... 1,200 square feet if located on a lot one acre or greater; 800 square feet if located on a lot less than one acre.
A Baltimore County building permit is required for any shed, gazebo, or accessory structure larger than 120 square feet. The structure must sit in the rear yard, be set back at least 2.5 feet from side and rear lot lines, and cannot exceed 15 feet in height.
Baltimore County Residential Accessory Structure Permit guidelines (BCZR § 400)
A building permit is required for accessory structures greater than 120 square feet... Must be located in the rear yard behind the rear foundation wall line, unless a zoning variance is obtained... Must be located 2.5 feet from the side and rear property lines... There is a height limitation of 15 feet.
A detached garage is an accessory structure subject to BCZR Section 400: it must be subordinate in area to the house, sit in the rear yard, and meet the 15-foot height and 2.5-foot setback rules. Converting one to living space triggers an accessory-apartment Use Permit.
Baltimore County Zoning Policy Manual, A-6 (BCZR §§ 101, 400)
Section 101 of the Baltimore County Zoning Regulations states that an accessory use or structure is subordinate in area to the principal use or structure on the same lot. Section 400 of the BCZR indicates that an accessory use or structure must be located in the rear yard of the principal use or structure.
In Baltimore County a carport is an accessory structure. If it is attached to the dwelling by an open projection such as a deck, porch, or patio, it must meet the principal dwelling setbacks, not the more lenient accessory-building setbacks in BCZR Sections 400.1 and 400.2.
Baltimore County Zoning Policy Manual, A-7 (BCZR §§ 400.1, 400.2)
If an accessory structure/building (garage, pool, shed, pool house, accessory apartment) is to be attached to an existing dwelling by an open projection (such as a deck, porch, patio or carport), it must meet principal dwelling setbacks, not the requirements of Section 400.1 or 400.2, BCZR.
Baltimore County has no separate tiny-home zoning category. A tiny house on a permanent foundation can qualify only as an accessory apartment in a detached accessory building under BCZR 400.4, capped at 1,200 sq ft (1+ acre) or 800 sq ft (smaller lots), family-occupied, with a Special Hearing.
BCZR § 400.4.B (Accessory Apartment in detached building)
The size of the accessory apartment may not exceed: 1,200 square feet if located on a lot one acre or greater; 800 square feet if located on a lot less than one acre, and the accessory building shall comply with the requirements of Section 400.
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